Research On Polarization Waveform Design Methods For Colocated MIMO Radar

According to the spacing of antenna array elements,multiple input multiple output(MIMO)radar is classified as distributed MIMO radar and colocated MIMO radar.The characteristic of colocated MIMO radar is that antennas are placed close to each other and the transmit waveforms of different antennas are different.As the result,it has the capability of waveform diversity which brings more freedom for optimization.Therefore,the colocated MIMO radar waveform design has always been a research hotspot in the field of radar signal processing.In the thesis,the waveform design method for colocated MIMO radar communication integration(RCI)and the polarization waveform design method for colocated MIMO radar are studied from the perspective of transmit waveform design for colocated MIMO radar.The main work of the thesis is as follows:1.A waveform design method for time-division colocated MIMO RCI is proposed.A colocated MIMO radar platform is used to construct a time-division dual function radar communication(DFRC)system.The system simultaneously transmits different data streams to multiple communication users in the communication mode.Different from the traditional precoding method based on communication channel state information,the method proposed in the thesis generates a desired constellation diagram based on the transmit data stream.Then the phase-encoded signal transmitted by the DFRC system is optimized under constant modulus conditions.That the communication users synthesize the desired constellation diagram with the signals received is the optimization goal.Then three waveform design criteria are constructed.By using the sequential quadratic programming(SQP)algorithm to solve the problem,the optimized transmit waveform is obtained.Numerical simulation results show that the DFRC system transmits the optimized phase-encoded signal and multiple communication users can effectively synthesize the desired constellation diagram.At the same time,it is difficult for eavesdroppers in the non-communication direction to decode the correct communication information from the received signals,which ensures the physical layer security features of the DFRC system.2.The polarization waveform design method for colocated MIMO radar under constant modulus condition is studied.The transmit phase-encoded signals are the optimization variables.Matching the desired transmit beampattern and suppressing the joint autocorrelation peak sidelobe level of the polarization angular signals are the dual optimization goals.Then the polarization waveform design criterion is constructed.By using the SQP algorithm to solve the problem,the optimized transmit waveforms are obtained.Numerical simulation results show that the colocated MIMO radar transmits the optimized phaseencoded signals and the polarization transmit beampattern can well match the desired transmit beampattern.The transmit energy is concentrated in the direction of the main lobe and the energy utilization of the radar waveform is improved.Besides,the auto-correlation joint peak sidelobe level is also effectively suppressed,which reduces the probability of false alarms triggered by the range sidelobes after the polarization angular signal pulse compressing and improves the detection performance for the radar target.