Research On Transmit Beam Pattern Synthesis For Circulating Code Array

Multiple Input Multiple Output(MIMO)Radar can adjust the working mode flexibly by exploring the transmit degree of freedom because of its application of transmit diversity technology.Compared with traditional phased array radar,MIMO radar is more adaptable to the complex and changeable battlefield environment.In recent years,new variables,such as time increment,have been introduced into traditional array configurations,and circulating code array comes into being.Because of the advantages of the new transmit diversity technology adopted by the circulating code array,the radar can design the transmit pattern more flexibly according to different working scenarios and requirements,and adjust the transmit waveform in time with the change of environmental information.Therefore,the synthesis of transmit pattern of circulating code array has become a very meaningful research field.This thesis focuses on the circulating code array radar.According to different requirements,the synthesis of transmitting pattern and signal processing methods are studied.The main work includes: 1.The characteristics of the transmit beam pattern of the circulating code array have been researched.The approximate solution of the transmit beam pattern is obtained by changing the beam pattern function of circulating code array into an equal ratio series,and then converting the problem of solving the transmit pattern into the problem of solving the zero of the sum function.Inspired by the principle of phase stationary in SAR imaging,the precise expression of the transmit beam pattern is obtained by considering the precise analysis of the transmit beam pattern using the principle of phase stationary.Using this feature,the main lobe direction of the transmit beam pattern of the circulating code array at any time can be obtained accurately.Finally,the characteristics of the transmit beam pattern in different pulse are derived.2.To deal with the problem of synthesis of transmit beam pattern of circulating code array,a method of synthesis of transmit beam pattern based on time-frequency equivalent circulating code is proposed.Based on the characteristics of transmit beam pattern,the analytical solution of the transmit signal parameters is given.The problem of transmit beam pattern design is transformed into the problem of solving transmitting signal parameters,which greatly reduces the computational complexity of optimizing the waveform covariance matrix of traditional MIMO radar in transmit beam pattern design.moreover,the design of signal parameters is based on LFM signal,the constant mode characteristic of radar transmitting signal can also be well satisfied.3.The current matched filter of circulating code array can not effectively use the coupled spatial DOF in the echoes,a new matched filter of joint transmit beamforming is designed by analyzing the characteristics of the echo signal of circulating code array.By analyzing the space-frequency two-dimensional characteristics of the transmit signals between multiple groups of pulses,a time-frequency equivalent cyclic coding array Anti-deceptive false target jamming method is proposed.The false targets can be completely filtered.Target detection and anti-jamming processing are combined by this method.The time complexity of signal processing is decreased in radar system.