Research On Pulse Compression Technology Of Multiphase Coded Signals

The unable resolve conflict between detection range and target exists in traditional radar systems. In order to solve this problem, the pulse compression technology is prompted and is rapidly developing. Its main principle is to compress the transmit wide pulse signal into a narrow pulse signal for processing. Pulse compression signal consists of linear frequency modulation signal, two phase coded signal and polyphase coded signals, of which polyphase code has lower sidelobe characteristics and strong doppler. Moreover, P4 code has the best performance of all the codes. So in this article the part dealing with polyphase code simulation all uses P4 code.This paper mainly researchs on pulse compression technology, the signal characteristics of polyphase code, polyphase code sidelobe suppression method and the project implementation of pulse compression system. First of all, the technology principle of the pulse compression and the two different methods to implement pulse compression system is introduced. Then further analyzes is done on the basic characteristics code and ambiguity function of several kinds of polyphase, like frank code and P code (mainly P4 code). Distance sidelobe produced by pulse compression can affect the radar’s judgement of the targe, So deep research on three classic sidelobe suppression methods namely window function weighted, sliding window two sampling processing and based on second-order cone programming is conducted to design mismatch filter. The simulation results show the effectness of them on the polyphase code sidelobe suppression. Combined with the point inverter characteristics of P4 code, the other two improved sliding window methods are proposed. i.e second order sliding window method and five point symmetrical sliding window method The two methods obtained good sidelobe suppression performance and better doppler tolerance. Then with the polyphase code FTF algorithm to design mismatch filter is presented. Through the analyze of simulation, it is concluded that the method can obtain strong sidelobe suppression, and has the advantages of small amount of calculation and fast convergence speed. Finally, the platform with FPGA is used to realize frequency domain pulse compression module, and verified the correctness of the system by Modelsim.