Continuous Wave MIMO Radar Beampattern Design Based On Phase Coded Signal

MIMO radar,with multiple transmitting antennas and multiple receiving antennas,has become a hot research focus nowadays because of its good ability of waveform diversity and high freedom degree.It can be divided into pulse wave radar and continuous wave radar according to radar system.Phase coded continuous wave radar is playing a more and more important role in modern wars since its wide time span,low probability of intercept,more distant horizon,better imperceptibility,etc.Based on the design of phase coded continuous wave radar transmitting beamform,the paper proposes methods of orthogonal waveform design and partial orthogonal waveform design.The main contents of this paper are as follows:In the first part the paper introduces the phase-coded signal.Common two-phase pseudo random codes are introduced,including m sequence,Gold sequence and Kasami sequence.The generant methods of these sequences and the properties are discussed and compared.Then the four-phase random code is introduced briefly.In order to be transmitted in the space,the baseband phase-coded signal needs to be modulated at the transmitting terminal and demodulated at the receiving terminal.Next the paper introduces the methods of modulation and demodulation of BPSK and QPSK signals.In the second part the paper makes a research on the orthogonal phase-coded design of continuous wave radar.Longer sequence signal is request for continuous radar,so the long orthogonal phase-coded sequence design is of great significance.This part discusses the concept and basic principle of the orthogonal waveform design.The basic principle is lowing autocorrelation peak side-lobe level and peak cross-correlation level.The idea of using genetic algorithm to optimize the waveform design is proposed.Then the method of longer two-phase orthogonal sequence is put forward.The main idea is extending the existing two-phase pseudo random codes and optimizing the codes using genetic algorithm to optimize the codes.The method of designing random length four-phase is proposed at the end of this part.In the third part the paper makes a research on the partial orthogonal phase-coded design of continuous wave radar.Two-phase signal and four-phase signal are designed to realize partial orthogonal waveform.The main idea focuses on the optimization of the transmitting waveform.The approach to solve this problem is parameterizing the square root matrix of the covariance matrix and making the constraints implied in the square root matrix.This converts the constrained beamform pattern to the unconstrained beamform pattern.The unconstrained module is optimized by using a quasi-Newton algorithm.Then map the covariance matrix of Gaussian random variables onto covariance matrix of BPSK symbol and QPSK symbol.The transmitting beamform of BPSK and QPSK are achieved at last.