Introduction of 80GHz band E-Band microwave applicationsOn December 4 the Ministry of Industry and Information Technology officially issued TD-LTE 4G licences to China Mobile China Telecom and China Unicom and China officially entered the era of 4G. According to a report by GSMA Intelligence a third-party analyst more than 128 countries will deploy about 500 LTE networks by the end of 2017. 4G not only provides more bandwidth and brings better mobile Internet experience to people but also challenges the carrier's mobile bearer network.With the issuance of 4G licenses in China the LTE network will be deployed quickly. However LTE base station coverage is small deployment density is much higher than GSM base station and 3G base station LTE construction will face a large number of new site demand and part of the new site shortage of fiber resources the domestic estimated 20% of the new site fiber resources missing making LTE base station service return and PTN fiber network loop are under pressure. As an important solution of mobile return microwave can replace or supplement optical fiber solve the problem of optical fiber shortage and realize the rapid deployment of LTE network. However the traditional microwave band (6-42GHz) is short of spectrum resources and the channel spacing is small (the maximum channel spacing is 28MHz at present in China) so it is difficult to meet the large bandwidth requirement of LTE base station for bearer network. In this case the industry has turned its attention to E-Band microwave which can provide large bandwidth. What is E-Band microwave how much bandwidth does E-Band microwave transmission provide and what application scenarios are suitable for?Introduction of E-Band band microwaveE-Band RF channel configurationIn 2000 ITU-R and ETSI standard organizations classified high-frequency 71-76 GHz and 81-86 GHz microwaves which were later referred to as E-Band.Fig. 1. definition of E-Band radio frequencyAt the same time ITU-R FCC and CEPT have made some suggestions on the radio frequency channel configuration of E-Band. The channel division is mainly 250MHz and 1.25GHz. It is precisely with 250MHz or even greater channel spacing resources that E-BAND microwave single-frequency point can provide greater bandwidth. At present the industry's largest single-frequency point bandwidth is up to 2.5Gbps. In the future it can even provide 10G air transmission bandwidth. Figure 2. E-Band radio frequency channel configuration defined by ETSI and FCCE-Band microwave transmission distanceThe transmission distance of microwave is affected by both free space loss atmospheric loss and rain attenuation. Next we focus on the transmission performance of E-Band microwave.Free space loss:The path loss of 71GHz to 76GHz is about 130dB and that of 81GHz to 86GHz is 131dB. This value is generally higher than the free space loss in the traditional frequency band which directly causes the transmission distance of E-Band to be much smaller than other traditional frequency bands.Air loss:As can be seen from the atmospheric window diagram below the attenuation of E-Band is very low in the range of 71 GHz to 86 GHz which is basically less than 0.5 dB/km.Fig. 3. atmospheric attenuation diagramRain failure:For microwave above 10GHz rain attenuation will directly restrict the distance of microwave transmission. For E-Band microwave in very serious cases such as rainforest rainfall (100mm/h) rain attenuation is around 30dB/km but this generally occurs only in a short period of time and in network design the allowance can be reserved to adapt to weather changes. Some manufacturers also support adaptive modulation function: that is by reducing the modulation mode to adapt to weather changes with the QOS configuration to ensure that high priority services can communicate normally thereby enhancing network reliability.E-Band is basically not affected by cloud and fog. Even if the visibility is 50 meters and the density is 0.1 g/cubic meter the E-Band can only produce 0.4 dB/km attenuation which can be neglected.From the actual test situation E-BAND microwave can work steadily in the range of 2 ~ 3km transmission distance.Application scenarios of E-Band microwaveCompared with the traditional frequency band E-Band has abundant frequency resources and supports wider bandwidth than the traditional frequency band. The single frequency bandwidth reaches 2.5 Gbps.Table 1 Comparison between traditional band and E-BandFrom the above analysis data E-Band microwave is very suitable for large bandwidth transmission application scenarios to meet the LTE bandwidth requirements for the return network combined with China Mobile's business needs we can roughly be divided into the following four scenarios.1. PTN access layer patch network:Loop network can improve the reliability and disaster tolerance of the bearer network. Operators usually have certain requirements on the network loop formation rate especially the pursuit of high quality China Mobile. However due to various practical difficulties and the lack of fiber resources in some stations a considerable proportion of the network access layer is still facing the pressure of loop formation. E-Band microwave can be used as an alternative to fiber optics to complement the existing network PTN equipment (the bandwidth of access loop is 1 Gbps at present) which solves the problem that the lack of fiber resources leads to the inability of PTN network to form a loop provides the protection capability of loop network for PTN network and improves the reliability of transmission network.2. LTE terminal base station access:In densely populated areas the bandwidth requirement of single base station (S333 configuration mode) is more than 900Mbps. E-Band microwave has abundant spectrum resources in 1-3 Km short-range scenario which can be used to solve the problems of resource shortage and transmission bandwidth of traditional microwave band. As the terminal LTE base station service access E-Band microwave can solve the problem of fiber missing in some new sites and realize the rapid deployment of LTE base station.3. major customer lines:For data service interconnection dedicated lines enterprise link leasing and other services with bandwidth requirements of more than 1 Gbps some buildings can not be deployed because of the difficulty of fiber laying high cost and long cycle. E-Band microwave can be used as an alternative fiber between IP/MPLS routers or L2 switches to solve the problem of fiber and deployment difficulties.4. integrated services access:E-Band microwave provides 2.5G wide bandwidth can easily carry base station/Wi-Fi large customers broadband and other services at the same time. In the absence of fiber and there is a demand for integrated services E-BAND microwave bandwidth advantages can be rapidly deployed to establish a leading brand attract more high-value customers.Fig. 4. four main application scenarios of E-Band microwaveE-Band spectrum has been opened in 47 countries E-Band microwave has been deployed in Europe the Middle East and other regions on a large scale Huawei has 40 E-band microwave commercial success in the world. But E-band microwave is still in the experimental stage in China. Recently China Mobile and Huawei have established the first E-Band test Bureau in China in Beijing Mobile Network. The physical link service test and reliability verification of E-Band have been completed providing detailed experimental data and technical evaluation for spectrum opening. At present the test Bureau bears the LTE service of the existing network and PTN hybrid group protection ring network providing high quality large bandwidth protection.
Tiantong No.1 WX mobile system to date the most detailed "spoiler"For a long time WX communication has played an important role in field exploration border patrol earthquake relief and other activities because of its advantages of wide coverage flexible networking and not limited by geographical environment.However due to the insufficient number of small terminals various types of equipment and the lack of interconnection and interoperability the rapid mobile communication needs of rescue teams are still not met.Against this background the WX mobile system came into being. This article will give you a detailed explanation of the origin and development of WX mobile system.First the WX is going to run.In July 2008 academicians Sun Jiadong and Shen Rongjun jointly wrote a letter ** calling for speeding up the construction of China's own WX mobile communication system.After more than three years of demonstration and design in 2011 China's first WX mobile communication system - Tiantong No. 1 WX mobile communication system project officially started.Tiantong-1 WX mobile communication system is a WX mobile communication system independently developed and constructed in China and also an important part of China's spatial information infrastructure. The system consists of space segment ground segment and user terminal. The space segment is planned to be composed of multiple geosynchronous orbit mobile communication WX.In August 6 2016 WX was launched successfully in Xichang. At present WX is carrying out on-orbit testing ground applications operation and control systems are undergoing integrated joint testing soon the whole system will be officially operational.Two. About Tiantong WXAt 0:22 on August 6 2016 China successfully launched Tiantong-1 01 satellite into space with Long March No. 3 B carrier rocket at Xichang WX launch center which is the first launch star of China's WX mobile communication system.Tiantong No. 1 WX is based on Dongfanghong No. 4 platform. The launch weight is 5400 kg. The design life is 12 years.Tiantong-1 WX has 109 land-point beams which cover the territory territorial sea and within the chain of one island. At the same time there are two sea-area beams covering the western Pacific (within the chain of two islands) and the northern Indian Ocean (the Bay of Bengal the Andaman Sea).Operating frequency band: User link is S band feeder link is C band both the uplink and downlink transmission of user link and feeder link are FDD / TDMA / FDMA mode. It can support 1 million users at the same time.On August 13 Tiantong-1 WX communication antenna was successfully launched; on August 18 Tiantong-1 WX transponder was successfully opened.At present WX is carrying out on-orbit testing ground applications operation and control systems are undergoing integrated joint testing soon the whole system will be officially operational.Three. Ground operation: the exclusive paragraph is being replied.Tiantong No.1 WX mobile system is responsible for system operation and publicity and promotion by China Telecom WX communications.China Telecom is the only operator with WX mobile communication license in China's basic telecommunications operators operating the Tiantong-01 satellite ground service exclusively providing customers with "space-earth-air integration" of all-round communication security services.It is understood that as Tiantong No. 1 WX mobile system "operational responsibility" China Telecom Group WX Communications Co. Ltd. next generation WX Mobile Communication Development Center Deputy General Manager Han Miao recently said that the Ministry of Industry and Information Technology is approving new segment resources dedicated to Tiantong No. 1 ground mobile communications.Four terminal supports Android system seamless switching with ground 4G network.At present the terminals supporting Tiantong-1 WX mobile system include hand-held portable on-board data acquisition and other forms.Let's talk about the handheld terminal that we care most about.At present the mobile terminal which supports Tiantong-1 WX mobile system adopts Android operating system and supports Chinese user interface. The interface application program and operation mode are basically the same as ordinary mobile phone. It can operate skillfully without training.What is even more surprising is that the mobile phone is multi-mode and compatible with ground 4G mobile communication.Other data: mobile phone supports 1.2 kbps-9.6 kbps voice data SMS services and positioning functions; weighs less than 250g standby time 72 hours working time 6 hours.Five. Various types of business that can be provided.According to the introduction Tiantong-1 on-orbit test shows that Tiantong-1 WX mobile system has been able to basically achieve all the functions of ground communications.Voice can dial any global fixed and mobile phone.Short messages which support short messages in and out of the network can be interconnected with the public mobile terminals on the ground.Fax rate 9.6kbps;Beidou positioning function all terminal products are built-in Beidou receiving capacity support based on Beidou / GPS position management and control;Data transmission/Internet access/video return data transmission rate 9.6-384 kbps Internet access rate 64-384 kbps.After that it will provide a variety of value-added services including voice value-added services access services cloud services intelligent network services online data processing and transaction processing services storage and forwarding services multiple communications services information services communications services.Six about the futureThe launch of Tiantong No.1 01 star is just the beginning of WX mobile communication system in China.According to the plan Tiantong 1 02 and 03 stars will gradually evolve using the new Dongfanghong 5 WX platform improve the power of the whole satellite and antenna caliber to support broadband communications with greater capacity.After the launch they will be deployed on the 01 sides of the East and west respectively forming a normal coverage of the Middle East Pacific Ocean the India ocean area and the "one belt and one road" area.With the development and popularization of the WX mobile system Tiantong-1 will play an important role in improving the level of mobile communication and emergency communication in China. It will become an indispensable information infrastructure for economic construction and national defense construction and meet the needs of the government the army the industry and the public. User needs.
The second generation of E-Band microwave: the choice of LTE EraWith the rapid development of mobile broadband the network capacity is growing rapidly. As one of the main return modes of bearer network microwave network is facing the dual challenges of super-large service capacity and densely deployed stations. Traditional band microwave (6-42GHz) spectrum resources are becoming increasingly scarce bandwidth capacity is limited it is difficult to meet the G-bit-level large bandwidth stations to return the demand and E-Band microwave (80GHz) because of its rich bandwidth resources large transmission capacity low spectrum usage fees and high-frequency narrow beams to adapt to intensive deployment and other advantages gradually from the traditional enterprises. The application of the industry market to the carrier class large bandwidth business bearer network development.E-Band can deal with large capacity backhaul easilyE-Band is the microwave frequency band of 80GHz (71-76GHz and 81-86GHz) which is the highest frequency band for commercial microwave communication. According to the ITU-R spectrum allocation proposal (see Fig. 1) E-Band can be divided into 19 to 250 MHz subbands according to ETSI standards with a wider modulation channel spacing than conventional microwave bands enabling E-Band microwave communication systems to transmit more than G bits of capacity. Business. With high-order modulation E-Band microwave can realize 1-5 Gbps even more than 10 Gbps high capacity space port transmission.E-Band microwave naturally has the capability of transmitting large capacity business. Taking a GSM/UMTS/LTE co-station as an example assuming that its maximum return service capacity is 400 Mbps (of which LTE service is 300 Mbps) the conventional microwave (6-42 GHz) needs to occupy the maximum sub-band of 56MHz in the spectrum definition which can only meet the transmission bandwidth requirement under 256 QAM modulation which is almost not used. The maximum capacity of conventional band microwave can be achieved when capacity is enhanced.For E-Band microwave the transmission of 400 Mbps only needs one 250MHz (E-Band minimum subband) in the standard definition which can be easily accomplished in the minimum modulation mode QPSK. If high-tone mode (such as 64QAM) and two 250MHz bands (500MHz) are used the E-Band can achieve 2.5Gbps of ultra-large transmission bandwidth. For the actual deployment and planning of GSM/UMTS base station although its single station capacity is generally less than 100 Mbps but in larger aggregation stations still face the need to converge to the core network to transmit Gbps-level service capacity which means that E-Band is also suitable for the wireless transmission of metropolitan aggregation nodes.In addition E-Band is located in the 80GHz high frequency band with very narrow beam angle the interference of spectrum reuse is relatively small suitable for dense LTE access network in the actual frequency planning can flexibly combine one or more 250MHz granular sub-bands with adaptive modulation (AM) and adaptive channel adjustment (AC) technology may be dense in urban areas. Set deployment of the return network more flexible and effective spectrum planning convenient for multiple operators in the same area at the same time deploy E-Band microwave.At present more than 40 countries and regions around the world have opened E-Band bands. Most of them adopt free or low-cost strategies for the management of E-Band spectrum in order to encourage and promote more applications alleviate the growing shortage of microwave spectrum resources and minimize and protect the investment of operators in the spectrum.Second generation E-Band for future telecom level applicationsAt present E-Band microwave is mostly used in enterprise transmission scenarios. It has many shortcomings in transmission capacity spectrum efficiency network characteristics and management. Specifically it only supports low modulation mode (BPSK) the maximum transmission capacity is only 1 Gbps and needs to occupy 1 GHz frequency band to realize and the spectrum efficiency is very low. Packet data characteristics L2 or L3 functions through external switches or routers to achieve; Synchronization characteristics deficiency no or only support synchronous ether not support IEEE 1588v2; Lack of perfect network management functions only provide the most basic configuration and management; Mainly used in the enterprise market can not meet the requirements of telecommunications network equipment. High reliability; less deployment narrow application area high cost of devices and equipment no scale delivery and maintenance capability high overall TCO.With the rapid development of LTE network the demand for single-station transmission capacity will grow to G bit level in the future. LTE also puts forward higher requirements on data characteristics synchronization management and many other aspects. Obviously the first generation of E-Band microwave products based on enterprise applications can not meet LTE's demand for large bandwidth high performance and low cost return. To this end leading microwave manufacturers have invested in the development of a new generation of E-Band products the second generation of E-Band microwave to adapt to future telecommunications applications emerged.In October 2012 Huawei took the lead in releasing the industry's first second-generation E-Band microwave products. The product's performance in transmission capacity packet characteristics synchronization network management and TCO reduction has been substantially improved compared with the first-generation E-Band.Super large transmission capacity and extremely high spectral efficiencyThe second generation E-Band supports 64QAM high-pitch technology. Without using the same capacity enhancement technology as Ethernet frame head compression 1.2Gbps transmission capacity can be achieved by using a 250MHz subband. If two 250 MHz subbands are combined the transmission capacity of E-Band microwave single link can reach 2.5 Gbps (2.5 Gbps transmission capacity can be achieved with 1 250 MHz Ethernet frame compression technology) which can fully meet the future demand of G-bit base station for super-capacity service. Compared with the first generation E-Band which takes up 1 GHz band to realize G-bit transmission the spectrum utilization of the second generation E-Band is obviously improved greatly.Advanced capacity enhancement technologyTo minimize the impact of weather and environmental changes on the microwave link the second generation E-Band microwave uses adaptive modulation and adaptive channel adjustment techniques to further enhance the link capacity and reliability supports adaptive modulation levels ranging from QPSK to 64QAM up to 6 levels with weather changes and 250MHz and 500MHz modulation. Frequency band dynamic adjustment can provide from hundreds of Mbps to 2.5 Gbps of fine elastic large bandwidth pipeline enhance the flexibility of site planning and deployment.Another important technology to improve the transmission efficiency of carrier wireless packet service is Ethernet frame compression technology (also known as "bandwidth accelerator"). The second generation E-Band supports deep Ethernet header compression. It can compress the two-layer Ethernet header (L2 Ethernet) and three-layer IP header (UDP/IP/IPv4/IPv6) in the Ethernet packet in the microwave space-port link. The transmission efficiency of short packet packets (Perfect clock synchronization mechanismClock synchronization is an important step in the deployment of microwave bearer network. The first generation of E-Band microwave only supports synchronous Ethernet technology to provide frequency synchronization which can not meet the phase synchronization requirements of LTE service bearer. Second-generation E-Band microwave supports synchronous Ethernet and full-mode IEEE 1588v2 (BC/OC/TC) deployment in various scenarios and adopts out-of-band synchronous transmission mechanisms to ensure accurate transmission of synchronous information in packet networks.Rich Ethernet data and network management featuresSecond-generation E-Band has rich network and management features: device/link/network-level protection mechanism; full-scale L2 Ethernet features; deep-level end-to-end QoS and SLA support especially L2 OAM which can timely complete all kinds of fault detection and location in complex networks; support MPLS-TP to provide reliable end-to-end packet service delivery. And management.Significantly reduce TCOIn addition to the lower spectrum usage cost of the E-Band band itself the second generation of E-Band products also use the design of telecommunication-grade products to provide high reliability; high-frequency spectrum efficiency and bandwidth can greatly reduce the unit bit transmission cost and power consumption; compact outdoor equipment structure multi-GE ports easy to expand; unique USB port configuration advantages For fast start and backup multi-functional (service/power/network management) line connection exempts tower maintenance; uses a network management platform that integrates with optical/router/microwave end-to-end... These characteristics can significantly reduce the TCO of carriers.Second-generation E-Band microwave can be used in large bandwidth convergence links and optical network ringing macro-station backhaul and high-density small cell micro-station access scenarios. It can well meet the needs of operators to build high-quality and ultra-wide bandwidth backhaul network. It is increasingly favored by operators all over the world. Vodafone France Telecom Deutsche Telecom Spain and so on. Leading multinational operators such as Dental Telecom Norwegian Telecom and Russian MegaFon have launched a second-generation E-Band business process. According to Dell'Oro's forecast the E-Band-dominated mega-capacity microwave market will continue to grow at an average annual rate of up to 26% over the next five years. E-Band products and technologies are also in constant development. Combining high-tone and MIMO wireless transmission technologies the transmission bandwidth of E-Band is expected to reach 5-10 Gbps in the future making microwave truly a reliable transmission platform with "fiber-level" capacity.
Intelligent radar and its key technologiesWith the rapid development of artificial intelligence technology and its gradual application in the military field intelligent radar and intelligent radar technology have attracted wide attention at home and abroad. Strengthening the research of intelligent radar and its key technology is not only the need of radar technology development but also the key to improve radar combat capability.1. IntroductionTraditional radar works mainly according to the pre-designed working mode. It has no ability to change the working mode automatically with the change of the target and environment and it has insufficient adaptability to the target and environment. Although adaptive signal processing technology has been widely used to improve radar anti-clutter anti-jamming and other aspects of performance but because adaptive signal processing requires the signal to be processed to satisfy the ideal conditions of stationary characteristics in order to obtain satisfactory performance so the actual combat environment especially under complex battlefield conditions adaptive signal processing. Signal processing is also limited. In order to meet the current and future operational requirements the radar system and technology must be further innovated and developed to continuously enhance the detection capability of radar in order to adapt to increasingly complex operational environment.The battlefield environment is complex and changeable under the condition of information warfare which requires that the radar must be able to change its working mode and parameters intelligently according to the requirement of combat mission and actual combat environment and select countermeasures independently. In order to achieve this we must add "intelligent" function to the existing radar design so that the radar can be "intelligent". The rapid development and deep fusion of modern radar technology and artificial intelligence technology will provide strong technical support for the development of "intelligent" radar i. e. intelligent radar.2 the basic concept of intelligent radar(1) AI technologyUp to now the definition and nature of "intelligence" is still an unsolved problem in scientific research. From the point of view of Engineering technology intelligence can be understood as "the ability to acquire and store knowledge and use knowledge to solve problems". Its basic characteristics are: perceptual ability; with memory and thinking ability; with learning and adaptive ability; with behavior ability. Artificial intelligence is a subject that studies machine intelligence that is using artificial methods and techniques to study intelligent machines or intelligent systems to imitate extend and expand human intelligence and realize intelligent behavior.Artificial intelligence is developed on the basis of in-depth study and mutual penetration of computer science information theory control energy system theory neurophysiology psychology linguistics mathematics philosophy and other disciplines. It is a highly comprehensive frontier subject and frontier science. It is also a new idea new theory and new science. Emerging disciplines emerging from technology. Since the advent of artificial intelligence it has experienced more than 60 years of tortuous development process has been widely used in many aspects of people's daily life and work and in the military field has a broad application prospects. At present artificial intelligence technology has entered a new period of development artificial intelligence in China has been highly concerned by the state and academia was written in the 2017 government work report.(2) the basic concept of intelligent radarThe concept of intelligent radar is in the process of development and formation. The understanding and understanding of intelligent radar will be deepened gradually with the deepening of research. At present there is no clear definition of intelligent radar at home and abroad. We think that intelligent radar can be understood in broad sense and narrow sense generally. In broad sense radar using artificial intelligence technology is intelligent radar. The application object of artificial intelligence technology can be part of radar subsystem or single radar system or radar netting system composed of multiple radars. In a narrow sense intelligent radar is considered as a kind of "radar with the ability of information acquisition knowledge learning autonomous reasoning and decision-making". It can change the transmitting signal form working mode processing mode and resource allocation independently according to the external target environment and task requirements in order to obtain better target detection tracking and recognition performance. . Compared with the generalized intelligent radar the narrow sense intelligent radar is an intelligent radar with higher intelligence.Considering the intelligent coverage it can be considered that the intelligence of radar subsystem is the primary form of intelligent radar the intelligence of single radar system is the intermediate form of intelligent radar and the intelligence of multiple radar netting systems is the advanced form of intelligent radar. Considering the depth of intelligent application it can be considered that the intelligent radar based on mathematical rules is a primary intelligent radar the intelligent radar based on empirical knowledge is a secondary intelligent radar and the intelligent radar based on data-driven is a high-level intelligent radar.Intelligent radar is the result of deep fusion and comprehensive application of modern radar technology artificial intelligence technology communication and information technology computer network technology and so on. It is an important direction of modern radar development.3 the development and trend of intelligent radar at home and abroad(1) overseas researchSince the end of the last century the Air Force Research Laboratory (AFRL) has been devoted to the research of intelligent signal processing. Its early research mainly focused on constant false alarm processing (ES CFAR) of expert system. Since then knowledge-based space-time adaptive processing (KB STAP) and digital map information-based space-time adaptive processing (KBMap-STA) have been developed respectively. P) research projects. AFRL and DARPA in the United States have sponsored many research projects such as knowledge-based radar (KB-Radar) Knowledge-Aided sensor signal processing and expert reasoning (KASSPER) Knowledge-Aided radar (KA-Radar) and automatic intelligent radar system (AIRS). In 2007 the US DARPA also listed KASSPER as one of the main directions of radar technology. In 2015 the United States DARPA launched the "Target Recognition and Adaptation in Competitive Environment" tracking radar target recognition project using depth learning technology to improve non-cooperative target recognition capabilities.In the 1980s and 1990s Guerci conducted a great deal of research in the field of cognitive radio and put forward the concept of "matched irradiation" which is essentially an intelligent allocation of irradiation power in space. Kershaw and Evans proposed in 1994 to transform the system into a closed-loop radar feedback system by adding an offline link from the receiver to the transmitter. In 2002 the United States Air Force Research Laboratory the Space and Missile Defense Command and the Navy Research Laboratory jointly organized the Waveform Diversity Task Force to carry out scientific research and experimental work on radar intelligent launching technology making major breakthroughs in frequency diversity array space-time coding array and so on.In 2006 Canadian Simon Haykin first proposed the concept of cognitive radar. Through Knowledge-Aided and adaptive launching it can realize the continuous interaction and learning with the environment obtain the information of the environment combine the prior knowledge and reasoning constantly adjust the parameters of the radar receiver and transmitter and self-adaptively detect the target. In 2007 Guerci proposed a knowledge-based cognitive radar system architecture. In 2013 the United States DARPA supported the Radar and Communications Shared Spectrum (SSPARC) research project. Based on cognitive radio and cognitive radar the communication and radar mutual transmission spectrum usage was realized and the mutual interference between radar and communication was reduced. In 2016 Greco extended cognitive radar to passive radar.In addition knowledge-based decision support performance evaluation simulation training fault diagnosis technology are also important aspects of intelligent radar technology research and very early began to become practical. In 1991 the United States Department of Defense formally issued the "Comprehensive Diagnosis" standard. As the main way to improve the operational readiness of the new generation weapon system and reduce the cost of support fault diagnosis using artificial intelligence technology has been applied to the new research radar system.Generally speaking although the concept of "smart radar" is seldom mentioned abroad a lot of research work has been carried out in the field of smart radar related technology and the technology maturity has been continuously improved. Many research results are on the eve of practical application and some of the research has become practical.(2) domestic research situationSince 2008 a number of domestic units have carried out research in the field of cognitive radar including environmental perception and description optimal waveform design adaptive signal processing and so on. At present there is a certain research foundation in the field of intelligent radar information processing and clutter suppression technology in China. The main research features are combining MIMO radar cognitive radar software radar and other research directions focusing on the formation of knowledge on the basis of statistical analysis of target and environment data and further using multi-waveform optimization. Adaptive processing and cognitive structure with feedback can improve the detection performance of radar system for weak targets clutter suppression performance and the utilization efficiency of radar system resources. In the research of intelligent radar target recognition technology there is also a more extensive research foundation in China including the use of neural networks support vector machines to classify and recognize the results of radar range profiles classification and recognition of SAR images. In addition in recent years China has also paid close attention to cognitive electronic warfare and carried out the preliminary research work which to a large extent promotes the research work of radar intelligent anti-jamming technology.Overall China has been following up and carrying out some research in the field of smart radar technology but there is still a big gap compared with foreign countries in the aspects of systematicness advancement and innovation. The system structure and technology system have not been established.(3) development trend of intelligent radarDeep intelligence. With the development of artificial intelligence technology the degree of radar intelligence is bound to deepen. At present adaptive algorithm processing technology based on mathematical rules has been widely used. Radar begins to have primary intelligence. Advanced intelligent radar based on depth learning will gradually appear in the future.Widely practiced. Just as the emergence of smart phones makes traditional mobile phones disappear quickly smart radar will be widely used in various combat platforms. Cognitive radar and Cognitive Electronic Warfare (CEW) follow each other like shadows constantly advancing in contradictions intelligent radar technology system itself will gradually mature through continuous learning.Multi function integration. Intelligence often means multi-function. With the development of active phased array technology digital array technology and software radio technology multi-function integrated intelligent radar which integrates the functions of air defense anti-missile and anti-defense will appear soon.Integrated RF integration. Detection reconnaissance interference communication attack control and evaluation are important elements of the future information war but the underlying technical mechanism is extremely compatible. In the future it will be the inevitable development trend of military electronic information technology to realize the above-mentioned integrated radio frequency integration based on intelligent radar technology under strong confrontation conditions and complex electromagnetic environment.Self organizing networking. Networking is undoubtedly an important direction of future radar development. There are two forms of future intelligent radar self-organizing network: one is distributed each radar has a higher intelligence; the other is centralized that is to set up a central base station only the base station radar has a higher intelligence.4 the key technology of intelligent radarThe goal of the development of intelligent radar is to enable the radar to have the ability of intelligent perception of environment processing information decision-making response control action and other independent behavior. In the process of promoting the evolution of intelligent radar from primary form to advanced form from primary intelligence to advanced intelligence the following smart radar gates should be broken through. Key technology to promote the continuous development of intelligent radar.(1) intelligent information processing technologyAiming at the targets with low radar cross section such as stealth aircraft and the complex ground/sea clutter environment this paper introduces the technical thinking of artificial intelligence uses various prior knowledge to form the knowledge base of the target and environment and adjusts independently through the process of machine learning analysis and judgment on the basis of continuously obtaining the target and environment characteristic information. The frequency waveform and energy of radar system can improve the performance of detecting and tracking weak targets. The main research contents include target detection and tracking technology based on prior knowledge radar information processing knowledge formation rule extraction and logical reasoning technology.(2) intelligent clutter suppression technologyAiming at the characteristics and difficult problems of strong clutter and high space-time coupling in the down-looking working environment of airborne early warning radar a priori knowledge of clutter environment is formed by continuous knowledge accumulation and learning based on artificial intelligence theory. Combining with advanced multi-waveform flexible transmitting technology of digital array radar the clutter suppression performance and complexity are improved. Moving target detection performance in clutter environment. The main research contents include clutter environment perception and parametric characterization technology radar emission pattern and waveform optimization technology.(3) intelligent anti-jamming technologyAiming at the characteristics of non-stationary and high dynamic changes of jamming signals in electronic warfare environment and the development of cognitive electronic warfare technology this paper adopts the theory and technology of artificial intelligence to accomplish cognition and decision-making quickly on the basis of real-time perception and learning of electronic warfare environment and multi-dimension such as time space frequency waveform polarization and so on. Resources evaluation and scheduling are carried out to achieve intelligent game under complex interference conditions. The main research contents include jamming environment sensing technology anti-jamming measures automatic optimization selection technology anti-jamming effect feedback and evaluation technology.(4) intelligent target recognition technologyAiming at the classification and recognition requirements of target types attributes and quantities in actual combat environment the machine learning theories and methods such as depth learning and support vector machine are adopted to complete the tasks of target and environment feature extraction and pattern recognition and realize the effective recognition of non-cooperative targets. The main research contents include target feature learning and recognition method based on depth network target classification and recognition method based on large data and small samples man-machine collaborative target recognition method and so on.(5) intelligent resource allocation and scheduling technologyAiming at the complex combat environment of radar such as multiple targets true/false warheads active/passive jamming and so on the complex scene discrimination calculation fast intelligent decision-making and flexible resource allocation are realized by means of artificial intelligence. The anti-jamming of real-time implementation system reasonable allocation of target tracking resources and effective implementation of key targets are solved. Identify complex problems and make full use of existing radar resources to improve radar operational effectiveness. The main research contents include radar resource intelligent dynamic scheduling and task planning technology radar resource intelligent dynamic reconstruction and real-time evaluation technology.(6) intelligent multi-source data mining technologyAiming at the requirement of improving command and decision-making ability of early warning operation this paper adopts the theory and method of artificial intelligence to organize classify analyze and interpret the large amount of data accumulated in the peacetime combat readiness training and test of radar system in order to accumulatively describe the information in the data and adaptively learns various numbers from different sources through artificial intelligence. According to the data the related information is found and the multi-dimensional information content is formed. Further experiments and operations are carried out to improve the intelligent support ability for early warning command and decision-making. The main research contents include knowledge model based on multi-radar data knowledge acquisition knowledge organization knowledge-based learning algorithm reasoning analysis and distributed intelligent radar network expert system and decision support system.5 concluding remarksAt present the development of radar equipment and technology is faced with many major challenges. What is the future of radar? How to develop future radar is a question that must be seriously considered and answered before us. The development of radar equipment and technology must not be "closed-door". It must follow the trend of the development of advanced technology merge new technology and speed up the pace of innovation and development. Artificial intelligence is a new frontier science which is developing rapidly. It is another revolution after the three industrial revolutions. With the development of big data and cloud computing technology artificial intelligence technology such as natural language understanding human-computer interaction intelligent decision-making control and so on may have great application breakthroughs in radar. Smart radar is a new concept of radar system. It is also an important direction of radar technology development in the future. Although the basic concepts and key technologies of intelligent radar are not mature and intelligent radar will face many great challenges from the engineering implementation the future development of intelligent radar should arouse our great concern. To adapt to the development trend of intelligent perception the deep integration of radar technology and artificial intelligence technology will make the future radar more intelligent thus bringing a bright future to the future of radar.
Definition performance parameters antenna type and feeder system of antenna systemAntenna system is composed of transmitting antenna and receiving antenna. The former is a transmission mode converter that converts the radio frequency current or electromagnetic wave of guided wave mode into the space electromagnetic wave of diffuse wave mode and the latter is a transmission mode converter of inverse transformation.As the transmitting antenna used in the mode conversion of guided traveling wave to diffusion wave the receiving antenna I used in the mode conversion of diffusion wave to guided traveling wave is called reciprocity theorem except that the transmitting antenna's power bearing capacity and voltage bearing capacity are far greater than the receiving antenna's both of them can be exchanged and the basic characteristic parameters of the antenna remain unchanged. Another important function of the antenna is to concentrate the energy of the electromagnetic wave that is to concentrate the energy in the transmitting direction while reducing the energy in other directions when it is used as the transmitting antenna; when it is used as the receiving antenna more energy can be intercepted from the incoming waves in the receiving direction while the incoming waves in other directions can be reduced by phase cancellation. This is the directivity of the antenna. Compared with the non directional antenna the increase of the energy concentration is called the gain of the antenna. The extended meaning of antenna directivity is negative gain (attenuation) in non-communication direction which can be used to describe another related performance index of antenna i.e. sidelobe (interference) radiation rejection of transmitting antenna or incoming wave interference rejection of receiving antenna in non-communication direction.1. Definition of mobile communication antenna system Definition and scope of antenna systemIn the mobile communication system the communication antenna is the converter of the communication equipment circuit signal and the space radiation electromagnetic wave. This paper mainly analyzes the antenna and feeder system in mobile communication system including base station / room sub-antenna related feeder cable and other radio frequency devices and related installation services.Two. Performance parameter description of base station antennaGe index1 working frequency band (Frequency Range)Working frequency band: whether antenna or other communication products always in a certain frequency range (bandwidth) depending on the requirements of the indicators. Under normal circumstances the frequency range that meets the requirements can be the working frequency of the antenna.The working bandwidth is called working bandwidth. Generally the working bandwidth of omnidirectional antenna can reach 3-5% of the central frequency and the working bandwidth of directional antenna can reach 5-10% of the central frequency.2. Input impedance (Input Impedance)Input impedance: the ratio of the signal voltage to the signal current of the antenna input is called the input impedance of the antenna. The input impedance of the general mobile communication antenna is 50 ohms.The input impedance is related to the structure size and working wavelength of the antenna. In the required operating frequency range the imaginary part of the input impedance is very small and the real part is quite close to 50_. This is necessary for the antenna to be in good impedance matching with the feeder.3. Voltage Bobbi (VSWR)Voltage Standing Wave Ratio (VSWR): The VSWR of an antenna is the ratio of the maximum value to the minimum value in the VSWR pattern generated along the transmission line when the antenna is used as the load of a lossless transmission line.The standing wave ratio (SWR) is generated by the superposition of reflected waves generated by the incident wave energy transmitted to the input of the antenna and not completely absorbed (radiated). The bigger the VSWR the bigger the reflection and the poorer the match. In mobile communication systems Bobbi is generally less than 1.5.4 isolation degree (Isolation)Isolation represents the ratio of signals fed to one port (one polarization) of a bipolar antenna to signals fed to another port (the other polarization).5 and three order intermodulation (Third Order Inter modulation)Third-order intermodulation signal: refers to two signals in a linear system due to the existence of non-linear factors so that the second harmonic of one signal and the fundamental wave of another signal to produce beat (mixing) after the parasitic signal.Intermodulation is the phenomenon of system performance degradation caused by two or more carrier frequencies outside the band mixing and falling into the new frequency components in the band.6. Power capacity (Power Capacity)Power capacity: The power capacity of an antenna is the maximum continuous RF power that can be continuously added to the antenna within a specified period of time without degrading its performance.Space radiation index7 gain (Gain)The ratio of the radiated power flux density of the antenna in a given direction to the maximum radiated power flux density of the reference antenna (usually using an ideal point source) at the same input power.Antenna gain is used to measure the antenna's ability to transmit and receive signals in a specific direction. It is one of the important parameters in selecting base station antenna. The higher the antenna gain the better the directivity. The more concentrated the energy the narrower the lobe.8 H/V-Plane Half Power Beam WidthIn the main lobe of the power pattern the angle between the beam widths of the two points which reduce the relative maximum radiation power to half or less than the maximum 3dB is called the half power lobe width.The horizontal half-power beam width is called the horizontal beam width; the vertical half-power beam width is called the vertical beam width.9. Electrical Down Tilt.The dip angle refers to the angle between the maximum radiation direction on the vertical radiation surface of the communication antenna and the antenna normal.The communication antenna is divided into fixed dip antenna and tuning antenna according to whether or not it supports electric dip adjustment: fixed dip antenna refers to the fixed dip antenna generated by configuring the amplitude and phase of the antenna radiation element array according to the wireless coverage requirements; and tuning antenna refers to the change of different radiation elements in the array through the phase-shifting element. Phase difference results in different radiation main lobe dip states. Generally the dip state of an electrically tuned antenna is only in a certain range of adjustable angles.10 front to back ratio (Front-to-Back Ratio)The antenna front-to-back ratio is defined as the ratio of the maximum radiation direction of the main lobe (specified as 0 degrees) to the maximum power flux density near the opposite direction (specified as 180 degrees (+ 30 degrees) F/B = 10 log (front-to-back power / backward power).11. Sidelobe suppression and zeros filling (Elevation Upper Side lobes & Null Fill)Side lobe suppression: The side lobe of the main lobe in the vertical direction (i.e. the direction toward the zenith angle) is called the superior side lobe. In order to cover the effect of base station antenna the antenna will be mechanically declined in network planning. This may lead to the antenna's first (or a certain angle range) upper sidelobe may be in a horizontal position or even lower than the horizontal position it is easy to cause adjacent interference so it is necessary to suppress it that is the upper sidelobe suppression.The upper sidelobe not only wastes the energy radiated by the antenna but also interferes with the adjacent cells especially the high-rise buildings in the adjacent cells. Therefore the upper sidelobe should be restrained as far as possible especially the first upper sidelobe with larger energy.Zero filling: refers to filling the first zero of the lower sidelobe in the vertical plane of the antenna with beam-shaped design to improve the coverage of the base station near the dead zone and reduce the near zone coverage and blind spots.12 cross polarization ratio (Cross Polarization Ratio)The difference between the power level of the antenna co-polarization receiving (the maximum receiving level) and the power level of the heteropolarization receiving (the minimum receiving level) within the beam width of Direction 3 dB13. Direction of roundness (Circularity)The pattern roundness of omnidirectional antenna refers to the deviation between the maximum or minimum level and the average value in the horizontal pattern.Average refers to the arithmetic average of the level dB value at a maximum interval not exceeding 5 degrees in a horizontal pattern.14. Polarization mode (Polarization)The electric field direction of electromagnetic wave radiated by antenna is the polarization direction of antenna. If the electric field direction of a wave is perpendicular to the ground we call it a vertical polarized wave; if the electric field direction of the wave is parallel to the ground it is called a horizontal polarized wave; if the electric field direction of the wave is at an angle of 45 degrees with the ground it is called +45 degrees or -45 degrees polarization.Three. Types of mobile communication base station antennasThere are many kinds of mobile communication antenna products with different models. According to the different application scenarios they can be divided into indoor distributed antenna products outdoor base station antenna products beautifying antenna products.I. indoor distribution and cell coverage antenna products.  1. ceiling antennaThe roof-absorbing antenna is generally used for indoor wireless coverage. According to its different radiation forms it can be divided into directional roof-absorbing antenna and omni-directional roof-absorbing antenna. The omni-directional roof-absorbing antenna can be divided into two types: unipolar roof-absorbing antenna and bipolar roof-absorbing antenna.2. wall mounted antennaIndoor wall hanging antenna is a typical small plate antenna product mainly used for indoor wireless coverage scene according to the different polarization mode can be divided into single polarization wall hanging and dual polarization wall hanging.3. Yagi antennaYagi antenna is mainly used for link transmission and repeater the cost is relatively low in the two-dimensional plane before and after the reflectance is better.4. log periodic antennaLogarithmic periodic antenna similar to Yagi antenna is a multi-element bidirectional antenna with broadband coverage mainly used for link relay.5. parabolic antennaParabolic antenna is a high gain bidirectional antenna consisting of a parabolic reflector and a central feed antenna.II. Outdoor base station antenna productsDefinition performance parameters antenna type and feeder system of antenna system1. omnidirectional base stationThe omnidirectional base station antenna is mainly used for 360 degree wide coverage which is mainly used to cover sparse rural wireless scenes.2. directional base station antennaDirectional base station antenna is the most widely used fully enclosed base station antenna which can be divided into several types including vertical polarization antenna vertical and horizontal polarization antenna +45 degree dual polarization antenna multi-band antenna and so on. It can be divided into fixed tilt antenna electrically tuned antenna and three-sector cluster antenna.3. electrically modulated base station antennaElectronically tuned antenna is a kind of antenna that changes the phase difference of different radiation elements in the array by phase shifting element and thus produces different radiation main lobe dip state. Generally the dip state of electronically tuned antenna is only in a certain range of adjustable angles. The electric dip adjustment has manual adjustment and RCU electric regulation.4. smart antennaA dual polarized radiation unit is used to form an array of directional or omnidirectional antennas which can scan the beam in 360 degrees or a specific direction; a smart antenna can determine the spatial information of the signal (such as the direction of propagation) and an intelligent algorithm for tracking and locating the signal source and can filter the sky in the spatial domain according to this information. Line array.5. multimode antennaMultimode base station antenna is different from common base station antenna in that it integrates more than two different frequency bands in a limited space. Therefore the emphasis of this product is to eliminate the interaction between different frequency bands (decoupling effect isolation degree near-field interference).6. multi beam antennaMulti beam antennas can produce multiple sharp beams. These sharp beams (called elementary beams) can be combined into one or more shaping beams to cover a particular airspace. Multi beam antennas have three basic forms: lens reflector and phased array.III. active antennaThe passive antenna is combined with the active device to form an integrated receiving antenna.4. Beautification antenna1. indoor beautification antennaThe beautification of different indoor distributed antenna products not only solves the problem of indoor signal coverage but also does not destroy the layout of finishing and decoration. It is.According to the shape of products indoor covering beautification antenna can be roughly divided into: ceiling lamp beautification antenna mural beautification antenna and exhaust fan and so on.2. outdoor cover beautification antennaThe outdoor covering and beautifying antenna mainly aims at the antenna application products such as residential area and base station. It camouflages and modifies the appearance of the antenna through the application of various materials structures and patterns without increasing the propagation loss. It not only beautifies the city visual environment but also reduces the public's fear and resistance to the radio electromagnetic environment. Emotion can also prolong the life of the antenna and ensure the quality of communication.According to the shape of the product the outdoor covering beautifying antenna can be roughly divided into: streetlight beautifying antenna logo beautifying antenna monitoring spherical beautifying antenna air conditioning beautifying antenna rockery beautifying antenna speaker beautifying antenna simulated tree beautifying antenna square column beautifying antenna chameleon beautifying antenna etc. Water tower beautification antenna fence type beautification antenna exhaust pipe type beautification antenna and so on.Four mobile communication feeder passive devices and othersThe feeder system is connected between the transmitter the receiver and the antenna. The feeder system is mainly used to transmit the high frequency power of the transmitter to the antenna and transmit the reflected signal received by the antenna to the receiver.The mobile communication system includes not only base station/compartment antenna but also feeder cable passive devices (such as combiner filter POI etc.) and other radio frequency devices. These are essential components of communication system. 1. RF feeder cableRF feeder cable can be divided into semi-flexible coaxial cable and semi-rigid coaxial cable; according to the different types it can be divided into 1/4 3/8 1/2 5/8 7/8 1-1/4 1-5/8 and other different sizes which are mainly used for indoor and outdoor radio frequency signal transmission.The RF cable inside the mobile communication antenna is also RF feeding cable which is mainly used for feeding jumper connectors power distribution network feeding network impedance matching and so on.2. way dividerThe combiner is mainly used to combine multiple system signals to a set of indoor distribution systems. In engineering application a set of indoor distributed system can work in different communication frequency bands simultaneously by using a combiner. The combiners used in mobile communication systems generally include two-way combiners three-way combiners four-way combiners and so on.3. filterThe function of the filter is to allow the signal which needs part of the frequency to pass smoothly while the signal of the other part of the frequency is greatly suppressed. The filter is generally divided into active filter and passive filter. Cavity filters in passive filters are commonly used in mobile communication systems. Their main characteristics are wide frequency coverage high reliability good stability input and output impedance matching easy cascade use flat in-band amplitude-frequency characteristics low insertion loss and high out-of-band suppression.4.POIPoint Of Interface multi system road platform. It is mainly used for indoor coverage of large buildings such as subway convention and Exhibition Center exhibition hall and airport. The system uses frequency combiner and Bridge combiner to introduce antenna-fed distribution system after combining multiple operators and multiple mobile signals so as to make full use of resources and save investment.To avoid interference POI is divided into two platforms upstream and downstream respectively the uplink and downlink signals are transmitted separately. POI is a bridge between the donor signal and the distributed coverage signal (leaky cable and antenna array) in wireless communication. Its main function is to combine and channel the upstream and downstream RF signals of each operator and filter out the interference components between each band. The main function of the upstream part of POI is to collect signals from different mobile phones through antennas and transmit them to the upstream POI through feeders. The signals of different frequency bands are detected by POI and sent to the base stations of different operators. The main function of the downlink part of POI is to synthesize carrier signals of various operators and different frequency bands and send them to the sky-feed distribution system of the coverage area. (MWRF junior editor)
Tiangong-1's curtain callOn April 2 2018 after accurate calculation and monitoring analysis by the Beijing Space Flight Control Center Tiangong I re-entered the atmosphere at about 8:15 on the same day landing in the central South Pacific Ocean and finally achieved a perfect farewell with its gorgeous posture. On September 29 2011 at 21:16:03 Jiuquan Satellite Launch Center launched from this moment on the sky belongs to China's target aircraft and space laboratory. The name "Tiangong" is mainly to cater to the diligent pursuit of unknown space in Chinese traditional mythology. The ancients regarded "Tiangong" as the most sacred place. The main tasks of Tiangong-1 are: completing the space rendezvous and docking mission with Shenzhou-8; guaranteeing the life and work of astronauts during their short-term residence in orbit ensuring the safety of astronauts; carrying out space applications (including space environment and space physical exploration) space science experiments space medicine experiments and space station technology. A short-term manned and long-term unmanned space experiment platform was preliminarily established to accumulate experience for the construction of the space station. Of course the prerequisite for accomplishing these tasks is to have a "supernatural powers" how does Palace One have these skills? All this comes from its two functional modules: resource module and laboratory module.Resource tank: The main task of the resource module is to provide energy support for Tiangong-1's flight and control its flight attitude. All the equipment of Tiangong-1's power subsystem (solar wing) is in the resource cabin and includes fuel to power the aircraft. The 6 control moment gyroscopes in Tiangong-1's navigation and guidance system are also in the resource capsule. The purpose of the navigation and guidance system is to find the target when Tiangong-1 docks with the tracking aircraft while the control moment gyroscope (CMG) controls the attitude of Tiangong-1 accurately.Experimental cabin: The open class of astronauts we are familiar with is carried out in the experimental module. Here the astronauts show us the miraculous phenomena of weightlessness water droplets floating candle burning (the shape of a flame is no longer in the shape of the ground but close to the sphere) and so on so that we can understand the difference between the space environment and the ground environment.The experimental module is mainly responsible for astronauts' work training and life. The experimental module is divided into the front cone section the cylinder section and the rear cone section. After docking astronauts enter the fully sealed front cone and cylinder for work and training and some necessary life activities sleep and so on are mostly carried out here. The rear unsealed rear cone section is equipped with regenerative birth protection equipment.Of course astronauts in the sky also need to complete certain exercises the experimental cabin is equipped to make astronauts maintain a strong skeleton fitness zone so that the astronauts'health can be guaranteed so as to better complete the space mission.Although the Chinese are more practical there is no European and American equipment that "luxurious human experience" but in order to ensure the safety of astronauts cabin cabin lines sharp corners core equipment are necessary to isolate from the astronauts how is the palace one done? In this regard the designer has adopted the strategy of "hiding" to decorate all the things that astronauts do not need. The equipment exposed to the outside is designed with rounded corners which can avoid collision between astronauts and equipment and ensure safety. After all the space environment is different from the ground environment we can not help but ask: in weightlessness how do astronauts stop? The solution to this problem is the "hand and foot limiter". In Tiangong I there are various hand-foot limiters beside each area. The total number of hand-foot limiters which are about 30 cm long and made of brocade ribbon are ingeniously placed around the bulkhead. This "small body" device has a great effect it is the only "magic weapon" to ensure that astronauts in the state of weightlessness drift easy to exert their hands and feet is also the largest number of equipment in the cabin. Of course like us astronauts must have their own entertainment life in the sky. In order to ensure the entertainment of astronauts Tiangong-1 also provides the astronauts with a notebook computer for entertainment. Astronauts can use the notebook computer to surf the Internet post micro-blogs watch blockbusters play some songs and music they like or do it before going to bed. His entertainment activities.In November 2011 Tiangong-1 docked successfully with Shenzhou-8 making China the third country in the world to master space rendezvous and docking technology independently. On June 18 2012 the Shenzhou-9 spacecraft and the Tiangong-1 target spacecraft successfully rendezvous and dock and three Chinese astronauts entered the orbiting vehicle for the first time.In June 13 2013 Shenzhou ten spacecraft successfully completed the automatic rendezvous and docking with Tiangong-1. After the return of Shenzhou ten spacecraft Tiangong-1 completed its main mission. Of course because the quality of the Chinese-made Tiangong-1 is so good that it is far from its age limit the Space Academy has given it other tasks: testing the power generation capacity of solar cells backup attitude measurement and control mode switching 4B engine orbit change and a series of pull-offs and backup flight mode tests. Du explored the flight potential of Tiangong-1 and created better conditions for space environment exploration and earth observation.Around 8:15 on April 2 Tiangong-1 re-entered the atmosphere and landed in the middle of the South Pacific Ocean. Most of the devices were ablated and destroyed during re-entry. It left a brilliant arc in the air. At this point Tiangong-1 was a perfect curtain call for China's space station exploration program. The answer to beauty.
Discussion on consistency stability reliability and measurement of antenna1. IntroductionWith the continuous development of mobile communication mobile communication antenna has experienced the development process from single polarization antenna dual polarization antenna to smart antenna MIMO antenna and even large-scale array antenna. After the great development of 4G China Mobile now has about 1.5 million base stations and the quality of antenna feeds is uneven. As the perception organ of mobile communication network antenna is more and more complex and important in the network. Although antenna investment accounts for a small proportion (only about 3% of base station investment) more than 40% of network failures are caused by antenna feed system. The degradation of antenna-feed system quality will lead to poor coverage performance or interference problems. As a complex passive product antenna is difficult to monitor in the network.The antenna-feed system problems are manifested in many ways such as: after two or three years of using the antenna in the network the network coverage performance has been significantly reduced the intermodulation interference is becoming more and more serious; the standing wave ratio alarm in rainstorm; the standing wave ratio alarm in windy weather; the same type of antenna used in the same manufacturer in the same network performance is very different and so on. These phenomena show that the reliability of the supplier's products is not high the quality of hidden dangers can not meet the requirements of product life indicators. How to judge? This is related to the consistency stability and reliability of the antenna. 2. Reliability of antennasIn general product reliability refers to the ability or possibility of components products and systems to perform specified functions without failures within a certain period of time and under certain conditions. Reliability of products can be evaluated by reliability failure rate and average failure free interval. Environmental reliability refers to the ability of a product to perform a specified function under specified conditions and within a specified time. In the process of design and application the product is constantly affected by its own and external climatic environment and mechanical environment and still needs to be able to work normally which requires testing equipment to verify it.Reliability includes three elements: durability maintainability and design reliability. Durability refers to the fault free or service life of a product. Maintainability means that when a product fails it can be quickly and easily removed through maintenance or repair.Design reliability is the key to product quality. Because of the complexity of man-machine system and the possible errors in operation and the influence of operating environment the possibility of errors still exists. Therefore the ease of use and operation of the product must be fully considered when designing. Design reliability. Therefore reliability is an important quality index but the qualitative description is not enough. It must be quantified in order to describe and compare accurately. Quantitative representation of reliability has its own characteristics and it is difficult to represent it completely by a characteristic quantity due to different use occasions.The reliability test of antenna products can be judged by a series of tests. Reliability test is an important means to investigate analyze and evaluate the reliability of antenna products. Reliability test of antenna includes high and low temperature test rain test vibration test impact test collision test vehicle transport test wind load test ice test and power test. The reliability of antenna product structure can be verified through environmental tests. As shown in Figure 1 the antennas satisfying the reliability requirements and the antennas not satisfying the comparison test results after the rain test vibration test and high power test are carried out.It can be seen from the diagram that the antenna with poor reliability can be checked by environmental test and the reliability of antenna product design material and process can be checked by environmental test.3. Stability of antenna performanceProduct stability refers to the ability of a product to keep its characteristics constant over time usually referring to the ability of product characteristics to change over time. Stability can be quantitatively characterized mainly by determining the relationship between characteristics and time. Stability is very important. How can we know if the system is stable?The stability and reliability of antenna products are inseparable. A relatively simple method to judge the stability of antenna products is to judge the reliability of antenna performance by the coincidence of index curve before and after reliability test. The study found that:(1) Radiation parameters are insensitive to process and circuit while circuit parameters are sensitive to circuit and process which can easily affect circuit parameters in production process especially in repeated debugging.(2) Among the circuit parameters the intermodulation order is too small and it is sensitive to test methods test equipment and environment so it is not suitable for statistical evaluation.(3) the circuit parameters are low on the test site and can be tested on the spot. The radiation parameters have high requirements for the reflection and shielding characteristics of the testing site and can not be tested on the spot.Therefore it is suggested to select the standing wave ratio and isolation of the circuit parameters as the stability characterization parameters of the antenna performance.As shown in Fig. 2 the VSWR curves of the antenna in the left-hand plot are in good agreement with those of the antenna before and after the vibration test but the VSWR curves of the antenna in the right-hand plot are still qualified after the vibration test (VSWR Fig. 3 compares the performance and stability of the antenna before and after the sprinkling test. It can be seen that the stability of the antenna isolation is better and the right picture is worse.Antennas with poor antenna stability can often pass the network access test but the quality of the antenna often decreases due to changes in the natural environment during the service cycle resulting in the decline of network quality which is easy to occur in the introduction.4. Consistency of antenna performanceThe consistency of antenna performance refers to the consistency of parameters of the same type of antenna products which can be judged by comparing the approximation of index curves of several similar products. As shown in Figure 4 the VSWR curves of multiple antennas of the same type have the same trend and smaller deviation which indicates that the VSWR performance of the antennas of the same type is consistent; the VSWR curves of multiple antennas of the right figure are irregular and cluttered indicating that the VSWR curves of the antennas of this type are consistent. Bobbi has poor performance consistency. Fig. 5 shows the consistency of antenna isolation performance and the same left-hand pattern antenna has better consistency than the right-hand pattern. Therefore it can be considered that the performance of the left antenna is better than that of the right antenna. 5. ConclusionAntenna belongs to broadband low Q passive products. The material structure will not be restored after damage in the reliability test process. The frequency change caused by thermal expansion and cold shrinkage of materials in high and low temperature test process is neglected. The change of test index after contrast test can reflect the stability of electrical performance index. It does not need to be tested in reliability test. Process test indicators. Intermodulation index of antenna is sensitive to manufacturing process and structure stability. Dynamic test can be taken to verify product stability indirectly.In short the reliability stability and consistency of the antenna have an important impact on the mobile communication network. It is important to measure and control the antenna performance before the antenna products enter the network.
Evolution of phased array antennas -- development and trend of conformal array antennasConformal array antenna is an antenna array that keeps consistent with the shape of the object. It conforms the antenna array to the shape of the carrier which enhances the adaptability and has great advantages over planar array antenna. In modern wireless communication systems conformal array antennas which can conformal to the surface of high-speed carrier platforms such as aircraft missiles and satellites and do not destroy the configuration and aerodynamics of the carrier have become a research hotspot in the field of antenna and an important aspect of the development of phased array radar in the new century. To. Among them flexible conformal array antenna (hereinafter highlighted) is a more advanced conformal array antenna technology not only can conformal with arbitrary curved surface can dynamically adjust and adapt to changes in shape but also for aircraft vibration and deformation caused by aerodynamic cold and hot changes have better adaptability. At present China the United States Japan are conducting related research China has developed a cylindrical array of phased array radar and helicopter conformal antenna.History of conformal array antenna technologyThe study of conformal arrays actually began very early. In the 1930s when radar appeared scientists began to study circular arrays conical arrays and other special shape antennas which were regarded as the basis and breakthrough of conformal arrays. Since the 1980s with the outbreak of the information revolution the rapid development of microelectronics technology a series of new devices and processes have laid a solid foundation for the application of conformal arrays. At present conformal arrays have begun to be partly practical and conformal phased array antennas have been used in various radars such as ground shipborne and airborne detection. Radar electronic warfare system communication system and so on are widely used. Technical characteristics of conformal array antennaThe traditional phased array radar antenna usually adopts linear array or plane array. Its advantages are simple structure easy technical processing and mature theory. Therefore the cost and cost are low. It is widely used in phased array radar antenna. However planar phased array antennas also have some inherent shortcomings which limit their further development.Determine the two parameters of radar detection distance: aperture and power. If we want to improve the detection range of radar we must increase the aperture of radar. However the space over the aircraft is limited and it is difficult to find a larger space for the plane array. Thus the conformal array appears. The most important characteristic of the conformal array is that it can conformal to the surface of the carrier. In this way the aperture of the radar antenna can be effectively expanded. The extended detection range is another advantage of the conformal array. It can extend the scan limit of the plane phased array to the hemisphere and even the 3/4 sphere region and during the scanning process. The performance of antennas and radars is not greatly reduced. In addition since there is no need to install radar in the aircraft the space inside the aircraft can be used to install other equipment and fuel thus increasing the load of the aircraft and making full use of the limited space in the aircraft. In addition conformal antenna can also help to improve the structural strength of the equipment reduce volume and weight.Compared with planar array antennas the analysis and synthesis of conformal array antennas is more complex. Generally speaking conformal array antenna synthesis is not only the synthesis of its pattern but also the design of the initial stage to consider the conformal array antenna shape array element form and its distribution. In addition the effects of conformal carriers and mutual coupling between elements on the resonant frequency bandwidth and polarization of the array and the array elements should be considered in the design. Therefore the design of conformal array antenna is a complex system problem it is difficult to have a strict and accurate solution to this problem usually using numerical analysis method to study. At present the commonly used numerical analysis methods are Moment Method (MOM) based on integral equation and its fast algorithm Finite Difference Time Domain (FDTD) based on differential equation and Finite Element Method (FEM). However the analysis of conformal array antenna moment method is usually based on the Green's function in the coordinate system conformal to the carrier platform. This method is very useful but it is very difficult for complex platform analysis. Research on conformal antennas in ChinaChina began to study conformal arrays in the 1970s and 1980s began to study conformal array antenna elements in the 1990s completed the prototype development began to develop conformal phased array antenna in the new century and exhibited CS/RB1 radar for the first time at the Zhuhai Airshow in 2012. From the related pictures it used cylindrical conformal array antenna. Phased array design with 360-degree detection capability working in L-band suitable for low-air defense rapid delivery and anti-fire operations can be used to detect enemy mortar shells and locate their launching positions as interception and counter-fire weapon systems of the alert and tracking radar but also can be used to correct their mortar fire; Man-portable can adapt to various transport aircraft helicopter airdrop requirements maneuverability easy operation deployment suitable for rapid delivery; in the air defense system to undertake all kinds of low-altitude targets detection tasks. The appearance of CS / RB1 radar indicates that the conformal phased array radar technology in China has moved from laboratory to army and international market. CS/RB1 cylindrical array phased array radar developed in ChinaThe first helicopter conformal antenna has been developed successfully in China.Recently the first helicopter conformal antenna independently developed by China Aviation Industry Group Co. Ltd. has been tested for its electrical performance. The results show that the test results of conformal antenna conformal to expectations marking the successful development of the first helicopter antenna in China and will be installed in domestic helicopter models.Research on conformal antennas in European and American countriesThe advantages of conformal array antennas have been recognized by developed countries such as Europe and America for a long time. However the existing conformal array antennas are mostly used in ground and Ship-borne Radar Antennas because they only design the conformal array into a given shape such as cylindrical or hemispherical passively adapt to the shape of the carrier. However due to the complexity of the environment the application of conformal array is more difficult.In 1960 the Naval Aviation Command began to study conformal phased array antennas for aircraft and missile skins. In 1973 the United States developed spherical phased array antennas and circular ring phased array antennas.The US Navy cylindrical conformal array can achieve 360 degree detection.According to relevant information the cylindrical conformal phased array antenna is used in the shipborne communication terminal of the US Navy Cooperative Warfare System. It consists of 96 array feeds. Each array has 10 elements connected by a microstrip antenna distribution network. The former Soviet Union has successfully developed a useful cylindrical conformal phased array antenna for air traffic control. Radar its maximum detection range can reach 400 km can achieve 360 degrees of detection can grasp up to 100 batches of targets the United States has also completed the use of optical control of the wide conformal phased array antenna development.In 2004 the U.S. Air Force and Raytheon began research on X-band thin phased array radar which uses conformal antennas. EADS in Europe is also developing a two-dimensional curved electronic scanning antenna for UAV testing. This kind of antenna array does not need mechanical devices. The curved antenna array is placed on the surface of the fuselage but becomes a part of the structure of the fuselage. It not only sends and receives electromagnetic waves but also weathered the wind and rain as well as the impact of foreign objects. The volume and weight are reduced and the reliability of the system is improved.The U.S. Air Force has also supported a number of conformal array antenna projects for example in the Structural Integration X-Band Array (SIXA) project a 64-unit conformal array antenna was installed on the wing of the Boeing 707 aircraft about 6 m in length and in the Sensor Aircraft Conformal Low-Band Antenna Structure (S-CLAS) project on the wing of the aircraft. Active phased array is installed at the leading edge to carry out conformal array radar system test. Adaptive processing can overcome the influence of fuselage deformation and wing jitter.These two projects only study the effect of wing bending on array performance and bending compensation technology and the closest application is the UHF conformal active phased array radar antenna manufactured specifically for this aircraft in the U.S. Air Force Sensor Craft project and integrated into the wing. The wind tunnel test has also been made into a X band conformal active phased array radar antenna 0.37m2.Research on conformal antennas in JapanJapan has always been a world leader in information technology and microelectronics and the accumulation of these technologies has provided a solid foundation for the study of conformal array antenna technology. The Electronic Equipment Research Institute of Japan's original defense technology research headquarters (which has been integrated into the Department of Defense Equipment) announced the flexible conformal array antenna that it is leading the research and development in 2013. It has a great breakthrough in practicality and solved the problems faced by most conformal array antennas.The development goal of this project in Japan is to replace the in-flight radar antenna for future aviation equipment. Its flexible conformal array antenna technology mainly realizes three points: the antenna can be bent at any angle; the antenna sensor can detect the curvature according to the bending state and automatically correct the electromagnetic wave phase; and the antenna is bent at any angle. By comparing the gain effect between curved state and plane state the technical feasibility of automatic correction of electromagnetic wave is verified. This kind of antenna developed by Japan is equipped with sensors which can detect the bending curvature of the antenna calculate the curvature radius to get the coordinates of each element and then automatically adjust the phase of each element to form a specified direction of electromagnetic beam. In the microwave anechoic chamber the gain effect of the flexible conformal array antenna is verified and the electromagnetic beam is formed in the specified direction which proves that the flexible conformal array antenna is effective to correct the electromagnetic wave. The objective of this flexible conformal array antenna technology in Japan is to make the nose diameter larger if large aperture antenna is needed in aircraft design. The flexible antenna technology can install the antenna outside the aircraft to match the surface shape of the fuselage replace the radar antenna in the aircraft and avoid the heat pipe inside the aircraft. And electromagnetic compatibility. The flexible conformal array antenna can adapt to any curved surface shape and its flexible conformal array antenna is light in structure small in weight and has good carrying adaptability. Comparing with the conformal antenna with fixed shape the flexible conformal antenna makes the antenna no longer need to be specially designed to suit the shape of the aircraft and can adapt to the shape changes of the aircraft aerodynamic and thermal expansion and contraction. New trend of flexible conformal array antenna technologyIf the flexible conformal array antenna technology is mature and has a wide range of military applications it will also change the traditional aircraft design concept. It will be of great benefit to improve the detection capability of combat systems especially in the rapid development of stealth aviation equipment today it has more practical significance.Firstly the flexible conformal array antenna can be mounted on the surfaces of different curvatures of the aviation equipment and the aviation equipment can be designed to the optimal aerodynamic shape without additional aerodynamic cost for the installation of the antenna array. Large early warning aircraft can make full use of the surface area of the fuselage and the large wing spans to lay the antenna which can greatly improve the detection capability and no longer need to carry extra antennas such as "disc" or "balance beam"; or high-altitude long-endurance UAV using flexible. The conformal array antenna can detect large aperture radar and meet the needs of wide area reconnaissance.Secondly the flexible conformal array antenna can not occupy the space inside the aircraft and the free space can be used to install other equipment and fuel so as to increase the load of the aircraft and make full use of the limited space inside the aircraft. In addition it can also help to improve the structural strength of the equipment reduce the volume and weight and help to improve the aircraft carrier. Mobility and the viability of the battlefield. This is a great advantage for space-compact aeronautical equipment such as fighters or missiles. If the fighters integrate conformal array antenna on the fuselage surface instead of the plane array antenna in the aircraft the nose space can be reserved for other more important airborne equipment which can carry more fuel to increase the range and can carry more airborne weapons. . If the conformal array antenna is installed on the surface of the radar guided missile the size and weight of the seeker can be reduced. The space saved in the missile body can install larger warheads or carry more fuel. It can also greatly reduce the size of the missile body to increase portability and maneuverability.Third the flexible conformal array antenna expands the scope of platform for situational detection. Any aircraft is easily adapted for intelligence gathering. Wings doors or fuselages can be used as antennas. Any manned or unmanned aircraft can perform surveillance tasks without developing specialized surveillance aircraft to accommodate radar antennas.Fourthly conformal array antenna can not only be used for radar detection and communication but also provide a new mode of electronic warfare operations greatly improving the effectiveness of electronic attack. High power aperture product (HPAPD) of large conformal arrays can be used to detect enemy communications and deal with many X-band radars and a large number of shortwave communications. Experts have envisioned using conformal array antennas to wrap missile-sized unmanned combat aircraft rapidly reaching enemy targets generating destructive peak power at close range thus conducting electronic attacks on enemy installations.Comprehensive summaryAlthough many countries have made great breakthroughs in conformal arrays some deep-seated problems still remain unsolved which limits the further development of conformal arrays. For example one of the most difficult problems in conformal arrays is to ensure that all elements of the array have the same pattern maximum direction and uniform polarization orientation. Each antenna element is not on a single array so the analysis and engineering implementation of conformal array is very difficult. In conformal array scanning the on-off switching and amplitude-phase weighting of antenna elements are multi-terminal and the power distribution and beam control of the corresponding feeder network need to be solved in real time. In addition in conformal array the elements in different positions have their own electrical environment. Therefore when the antenna works how to solve the problem of active input impedance matching needs to be solved. The key problem to be solved is that the vibration and dynamic deformation of the body have a great influence on the antenna array which needs to be solved in practice.
Why is the antenna tower very high?If you look at it a little bit you can see that the antenna towers are all high around you or you can just put a signal tower on a local high-rise.I never knew why I had to do this before but I took it for granted.However after learning the principle of communication recently the reason why the antenna tower is relatively high can be understood.Under the understanding of sight distance propagationLine-of-sight propagation (LOS propagation) refers to the propagation of space wave between two points that can be directly reached when ultra-short wave and microwave are used for ground communication and broadcasting. Its distance is similar to that of the people on the ground and generally does not exceed 50km.High-frequency (2MHz ~ 30MHz) electromagnetic waves known as high-frequency electromagnetic waves can penetrate the lowest atmospheric ionosphere but will be reflected back to the ground by the upper ionosphere the ground will reflect the electromagnetic waves back to the atmosphere thus producing the mode of sky wave propagation.Electromagnetic waves with frequencies higher than 30MHz penetrate the ionosphere directly. The signals of our mobile phones are ultrashort waves and the frequencies are much higher than 30MHz. Therefore the transmission of mobile phone signals belongs to the line of sight propagation.The antenna height is equal to h the earth radius R is 6370km and the Pythagorean theorem shows that:D2+R2= (h+R) 2beD is two antenna distance.D2= (2D) 2=8RhBring the value of R into the upper form.Formula: D for transmit receive antenna distance (km)Further explanation of tower heightGenerally the distance between transmit and receive antennas is between 20km and 50km. Many factors are taken into account such as high cost of tower long distance high power and high electricity cost.The distance D of the line-of-sight transmission is 50 km and the height h of the antenna is 50 m.Therefore the antenna tower is always high. (nodding manually)Knowledge extensionFrom the above we know that the normal distance of sight distance propagation is 50km. What about long-distance transmission? This can be achieved by wireless relay.In the case of the LOS propagation distance of 50 km an antenna tower can be built every 50 km and then the signal is transmitted every 50 km. And each tower receives and sends different frequencies otherwise mixing problems will occur resulting in the signal can not be restored.From the deduction of the formulas above we can see that the distance of LOS propagation is related to the height of the antenna. If we want to make the distance of LOS propagation farther we need to set up a higher antenna. But considering the cost of the antenna tower it is difficult to complete on the ground so we can consider to let the antenna go to the sky and use the satellite as the rotation. The station (base station) is also called satellite communication.However the delay of satellite communication is relatively high and the cost of satellite is not low after all it is not easy to go to heaven. The stratospheric communication is currently developing to solve this delay problem.This project is called the air base station and now some large companies such as Google and Facebook are doing this project. The advantages of using aerial base stations are obvious avoiding artificial laying of infrastructure such as fiber optic networks low cost and no need to worry about human destruction.But there are still many problems in the air base station such as how to maintain a stable high bandwidth how to maintain a reliable network environment these are very big problems because the air base station in the stratosphere will be affected by the weather the air base station wireless network technology needs to rely on microwave millimeter wave or FSO (since) It is implemented by a space optical communication system but microwaves have relatively low capacitance; millimeter and FSO are often affected by weather (millimeter waves do not work properly in cloudy and rainy weather and FSO performance is affected by dust and fog). And there's also the problem of unfixed displacement in the air base station which is caused by the Earth's rotation. This is a very big problem. If two wireless transceivers are five miles apart and one of them deviates from the normal position by only one degree the final signal will reach a target position that is nearly 500 feet offset from the original position. 
Israel is developing superchips operating at frequencies up to terahertz running 100 times faster.Known as the Middle East Silicon Valley Israel is highly advanced in science and technology. Its chip industry and semiconductor technology are particularly noteworthy. Annual exports account for more than 20% of Israel's total exports. At the moment Israel is developing smaller 100 times faster superchips than traditional chips promising.It is reported that Ulier Levy a physicist at Hebrew University in Israel and his research team have been working on a new chip technology. After more than three years of unremitting efforts the research work has finally come to fruition. Using the "metal-oxide-nitride-oxide-silicon" structure (MONOS) they developed a new integrated photonic circuit fabrication technology which allows the use of flash memory technology on microchips promising to make smaller faster-running photonic chips a reality with even too much computational frequency. The Hertz magnitude will increase the speed of computer and related optical communication equipment by 100 times.Terahertz (THz) is one of the units of frequency. Terahertz wave consists of electromagnetic waves with frequencies of 0.1 THz-10 THz which is a section of electromagnetic spectrum between microwave and infrared optical bands. Compared with the development of infrared and microwave technology on both sides of terahertz band people have limited knowledge of terahertz band forming the so-called terahertz gap. Terahertz wave has penetrability and less energy than X ray so it will not cause damage to human tissues and DNA. In recent years terahertz technology has become an interdisciplinary frontier of science and technology and has great potential in the field of microchip.In general optical communication encompasses all the technologies that use light as a carrier of information and transmit it over optical cables. For example the Internet e-mail SMS telephone cloud and data center are all in the category of optical communications. Optical communication is very fast but in microchip optical communication becomes unreliable and difficult to repeat and expand. Specifically there are two major technical difficulties that hinder the development and fabrication of terahertz microchips: one is that the chip itself is overheated and the other is that it is not scalable. Scientists point out that the ultra-high precision and reproducible fabrication of micro photonic devices is an important technical guarantee for the successful development of integrated photonic chips.Levi's scientific research team has made a breakthrough in these two problems. They skillfully circumvented the technical problems of low precision poor repeatability and poor expansibility in micro-and nano-fabrication of photonic devices and introduced flash memory technology into the fabrication of silicon-based photonic devices. This initiative has important prospects and pioneering significance for the coming of integrated photonic chips which is expected to trigger a revolution in the chip industry. Some analysts say the discovery will help bridge the terahertz gap and create new more powerful wireless devices that allow chips to transmit data at much higher speeds than they currently have a technology that could change the rules of the game in chip-based high-tech fields.In fact the shift from electronic communications to optical communications is attractive to chip manufacturers as optical communications can dramatically speed up chip operations and reduce power consumption after breaking down technical barriers. It is hoped that terahertz microchips which are 100 times faster than traditional chips will be available as soon as possible for the benefit of mankind.
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