Research On Optimal Selection And Coherent Integration Of Passive Radar

Passive radar has significant advantages in countering jamming signal,stealth target,antiradiation attack and low altitude penetration.As a common external radiation source,satellite digital communication signals have the characteristics of large angle of exposure,wide spatial distribution and large coverage of signals.However,the simultaneous interpreting of digital communication signals and traditional active radar signals is quite different,and there are great differences in signal processing.Usually,the ground receiving station can receive many digital communication satellite signals,which are distributed in different positions on the space orbit.In order to improve the target detection ability as much as possible,it is necessary to comprehensively consider the indicators of available external radiation sources,design appropriate external radiation source selection strategy,comprehensively evaluate all kinds of available external radiation sources,and finally get the optimal selection result.In addition,the external radiation source is located in the geosynchronous orbit far away from the ground,which leads to the extremely low power of the echo signal after the secondary scattering of the target,and it is easy to be covered up in the background clutter.In order to enhance the ability of target detection,it is necessary to effectively suppress the clutter of each channel before the correlation operation,so as to reduce the adverse effect of clutter interference on target detection.Considering that the satellite usually carries several signal transponders,the spatial position of each transponder is similar,the arrangement is regular,and the modulation style of the transmitted signal is similar.Therefore,the signal-to-noise ratio can be improved by homologous multi-frequency coherent synthesis.Based on the key project of a ministry,focusing on the engineering application requirements,this paper studies the system model,the optimal selection of radiation sources,and the coherent synthesis of multi frequency on the same satellite.The details are as follows:1.As the research foundation,this paper studies the external emitter radar system based on digital communication satellite,analyzes the spatial position relationship of satellite emitter,moving target and receiving station in the actual scene,studies the signal processing flow of the external emitter radar system,and deeply analyzes the emitter signal structure characteristics and ambiguity function properties.It is verified by simulation experiment.2.According to the demand of external emitter selection,an optimization method of external emitter selection based on membership analysis is proposed.Firstly,the performance indexes of the external emitter radar system are analyzed,and the system performance indexes of the external emitter radar are proposed from two aspects of detection performance and resolution performance,which provide the basis for the subsequent emitter selection.Then,a multiattribute external emitter optimization strategy is proposed,which transforms the multiobjective optimization problem into a single objective optimization problem by using the weighted method,and the consistency ranking method is used.And entropy method is used to design a comprehensive weight determination method combining subjective and objective,and then the nonlinear optimization selection result of external radiation source based on fuzzy comprehensive evaluation is obtained;finally,combined with the engineering project requirements and real satellite equipment parameters,the selection result of radiation source in the actual environment is obtained.3.The methods of clutter filtering and multi-frequency coherent synthesis on the same satellite are studied.Firstly,the cause of clutter in the receiving channel of the external emitter radar system is analyzed,the interference signal ratio of the receiving channel is calculated quantitatively,and the time-domain adaptive clutter suppression algorithm is studied,which is verified by the measured data of Asiasat-7.Then,the multi-frequency signal model of the same satellite is established,the position relationship between the signal transponders and the form of the transmitted signal are analyzed,and the phase terms of each receiving channel are calculated.The phase difference between channels is analyzed and compensated accurately,and then the phase compensated signals are synthesized coherently.The feasibility of this method is verified by simulation experiments.