| MIMO radar is an important innovation in radar technology and has better performance compared with phased array radar.These excellent performances are due to the use of multiple transmitting and receiving antennas which can freely select different radar signals and transmit orthogonal waveforms in the MIMO radar system.It is precisely because of such characteristics that the waveform transmitted by each antenna becomes an important factor affecting the performance of MIMO radar.Therefore,it is of great significance to design a good transmitting waveform for MIMO radar system.In this thesis,the basic principle of the orthogonal waveform is analyzed,and the research on the design and optimization of the orthogonal waveform of phase coded MIMO radar is carried out.The details are as follows:1.A kind of zero-correlation zone periodic complementary sequence set is constructed to solve the problem of waveform interference among multiple transmitting antennas of MIMO radar.The constructed ZCZ periodic complementary sequence set contains several subsets,because each subset can form a zero correlation zone sequence set,so that the signals emitted by the same antenna at different times will not affect each other in the zero correlation zone.At the same time,the sequence set formed by the sub-sequences of different subsets at the same position is also the zero correlation zone sequence set,so that the signals emitted by different antennas will not affect each other in the zero correlation zone.In addition,the number of subset and the number of sub-sequence can be set flexibly,which makes it more suitable for MIMO radar system.Experiments show that the constructed sequence set can be well applied to MIMO radar.The analysis of the ambiguity graph shows that the constructed sequence set has a good distance ambiguity function in the zero correlation zone.2.Aiming at the problem of MIMO radar transmitting orthogonal waveforms,an improved moth-flame optimization algorithm is proposed,and the correlation performance of the optimized phase coded signal set was optimized by this improved algorithm,so a nearly orthogonal MIMO radar transmitting signal set can be designed.In the improved algorithm,the flame searching process is added,so that the flame can not only save the optimal position of moth,but also search the optimal solution.The simulation results show that the improved method can obviously improve the convergence speed and accuracy of the moth-flame optimization algorithm,and the optimized MIMO radar transmitting signal set has low auto-correlation sidelobe value and cross-correlation value.3.A hybrid algorithm for the orthogonal waveform optimization of MIMO radar is proposed by combining moth-flame with differential evolution algorithm,which is used to improve the correlation performance of the transmitted signal set of MIMO radar.This hybrid algorithm not only has the advantages of large MFO search range and fast DE convergence,but also can make up for the disadvantages of slow MFO convergence and easy to lose the diversity of solutions.The simulation results show that the hybrid algorithm can improve the convergence speed and accuracy,and the optimized MIMO radar phase coding signal set has good correlation performance. |
