Research Of Suppressing Co-channel Interference Of Broad Timewidth Of Pulse Compression Radar System

As pulse compression radar system can perfectly deal with the contradiction between the reached distance and resolution, it is widely used. The large Time-Bandwidth Product signal is usually used as transmitted signal, which can guarantee low transmitting power and has the advantages of anti-interference and concealment. The pulse compression radar whose transmitted signal has large BT can have better detection performance. However, when ships sail in a line or radars form into network, the problem of co-channel interference will appear. Co-channel interference can lead to the increasing probability of false alarm, the falling probability of detection and can lower seriously the performance of interfered radar to detect and track targets.This paper mainly studies the methods of suppressing co-channel interference whose transmitted signal is linear frequency modulation signal. Firstly, the principle of pulse compression is introduced. Secondly, The characters of LFM signals in time and frequency domain and its ambiguity function are studied, then making simulations on the result of pulse compression, in order to inhibit side slobe, this paper introduces the method of adding window function to the coefficient of pulse compression, which must balance the relationship between the broadening of main lobe, SNR loss and mainlobe peak to sidelobe peak ratio. Thirdly, based on paired-echo theory, this paper simulates the influence on the output of the matched filter when LFM signal has distortion of amplitude, phase,frequency modulation slope and center frequency point. Fourthly, this paper proposes a method which combines independent component analysis with multi-pulse in time to suppress co-channel interference, this method suppresses co-channel interference by suppressing co-channel synchronous and co-channel asynchronous interference. Conventional against-asynchronism algorithm is used after pulse compression, which can bring the problem of false-alarm increasing as the sidelobe level is higher than the detectable level of radar, in order to avoid this problem, against-asynchronism algorithm can be used after digital orthogonal module and low pass filter. To this method, this paper also gives the result of simulation on suppressing co-channel interference. At last, Based on the actual signal processing process of pulse compression radar system, this paper proposes two methods to suppress co-channel interference, and simulates the effect of the two methods to suppress co-channel interference.