Waveform Design For MIMO Radar And Research On Target Characteristics

Multiple- input multiple-output(MIMO) radar which prompted by the development of MIMO technology can improve the performance of all aspects of the radar system, so it has attracted wide attention. The design and optimization of orthogonal waveform is a critical component for MIMO radar that transmits omnidirectional orthogonal or non-coherent non-contiguous waveform to replace the coherent signals emitted by traditional phased array radar.The generation and orthogonal characteristics of OFDM-LFM waveform and OFDM-NLFM waveform are analyzed according the characteristics of transmit diversity MIMO radar. The design method of OFDM-NLFM based on optimization of combined windows is studied, and the high resolution range profile(HRRP) of targets under the system of MIMO radar is realised. The details include:Firstly, orthogonal frequency division multiplexing linear frequency modulation(OFDM-LFM) chirps are realised based on orthogonal frequency division multiplexing(OFDM) technology and linear frequency modulation(LFM) chips. And then the orthogonal performance of this kind of signal is analyzed. In the simulation of point target matched filtering, we can get that the OFDM-LFM signals substantially meet the orthogonal requirements.Secondly, orthogonal frequency division multiplexing nonlinear frequency modulation(OFDM-NLFM) chips are realised when non- linear frequency modulation(NLFM) chips which have low side- lobes and don't need weighting are introduced, and the simulation results confirm the better auto-correlation and cross-correlation performance of this radar signal. Although the OFDM-NLFM signal has lower auto-correlation peak side- lobe and cross-correlation level, it has a disadvantage of a wide main- lobe. For the contradiction between the main- lobe width and side- lobe level, the non- linear frequency modulation chirps are optimized using combined windows based on the effect of combination parameters on the ratio of main- lobe peak to side- lobe peak(RMS) and main- lobe width. Furthermore, a novel signal design method named of orthogonal frequency division multiplexing NLFM is studied by means of combined windows. At last, point target echo of the designed signal is processed using matched filter. The simulation results confirm the good orthogonal performance of the optimized radar signal.Finally, a kind of calculation model which aims to calculate the high resolution range profile(HRRP) of targets is presented in this thesis. By using orthogonal signal of MIMO radar as the transmitting signal, radar echo is obtained by means of physical optics method to solve the radar cross section(RCS) and HRRP will be acquired after the processing of matched filtering. The simulation results confirm the validity and accuracy of the method of calculating target's HRRP based on MIMO radar by comparing with the HRRP obtained by the stepped frequency signal.