Key Technologies Of Communications Reconnaissance Systems Based On Reconfigurable Antenna

As the development of the modern communication technique, the radio signals in the air aremore and more, and the frequency band broaden gradually, which result in crowdedelectromagnetism environment and interference between the signals increasingly. Together withthe channel attenuation, which seriously affect the normal reception of the signals. Especially asa third party to receive, antennas are often in sending the signal pattern sidelobe, so thereceived signal SNR lower. These unfavorable factors give radio detection income it difficult.The reconfigurable antenna can solve the problem of electromagnetic compatibility byusing the ability of reconfigure, that is, reconfigurable antenna can adaptive change according tothe electromagnetic environment and pattern. At the same time, the reconfigurable antenna isgood at adapting to environment, which can suppress the external interference effectively andimprove the quality of receiving signals. This will be of great significance in reconnaissancesystem.The reconfigurable antenna needs some technical support, such as optimization algorithmand the automatic controller switch. This thesis mainly focuses on the innovative studies of thekey techniques in communication reconnaissance system based on the reconfigurable antenna asthe following points:1. A research program of communication reconnaissance system based on the reconfigurableantenna is put forward from the realization of the application of the reconfigurable antennain reconnaissance system. A comparison of receiver performance between reconfigurableantenna and ordinary single-antenna is made by the signal generator making an actual signalof low signal to noise ratio, which shows that the signal intensity of reconfigurable antennais larger than that of ordinary single-antenna. This primarily proves the feasibility of theapplication of reconfigurable antenna in the reconnaissance system.2. A reconfigurable antenna of mesh is proposed. The special mesh structure with highinvisibility creates the conditions for the application of reconfigurable antenna in the tacticalreconnaissance, at the same time, the antenna can make the simple switch control and adjustthe antenna to the best receiving state According to the feedback of a certain parameter ofreceiving signals.3. A algorithm which uses genetic algorithms to quickly search for reconfigurable antenna forbest reception state is proposed. The reconfigurable antenna has223（8388608）structure ofstates, so the search algorithm must be combined with high efficiency in the use of thismulti-structural state of the reconfigurable antenna. The genetic algorithm is a probabilisticsearch algorithm with implicit parallelism, which objectives function as the only searchcriteria,. At the same time, the search range is fixed at high fitness space, which greatlyimprove the efficiency of the search.4. An effective method of signal detection is proposed. The new method uses SNR as theobjective function of the genetic algorithm and to measure the performance of the antenna receiving. In this paper, the new method achieves SNR estimation at low pretreatmentrequirements.5. The automatic antenna switch controller is designed and produced. According to theCommunication Protocol made in this thesis, the PC can make switch instructions to thecontroller by serial ports, and then the controller transmits the information of the switch stateto the antenna by data lines, which can achieve the automatic control of the switch of theantenna state.6. Communications detection based on reconfigurable antenna test can be realized by sendingactual signal. The test results show that the system can effectively suppress interference andimprove the signal quality. At the same time, the system can initial goal in practice.