| The requirement on battlefield perception ability is higher than ever in modern information war. As a kind of high precision battlefield perception tools fitting all-weather and long-distance, radar plays an important role in the modern information war. Based on MIMO technology in civil communication field, Multiple Input Multiple Output (MIMO) radar uses multiple array elements simultaneously at the transmitter and receiver, and applies waveform diversity technology to effectively improve the comprehensive performance of radar. Orthogonal waveform design of MIMO radar studied in this paper is the key problems to realize MIMO radar, which also is a critical factor to the final performance of MIMO radar.The main work in this thesis is summarized as following:(1) Study and analyze the principle and signal processing method of MIMO radar, in order to summarize the design standard of the MIMO radar orthogonal waveform. It indicates that the good performance of the orthogonal waveform should have lower autocorrelation side lobe peak and cross correlation peak.(2) Apply frequency division multiplexing principle to design the orthogonal waveform of OFDM-LFM (Orthogonal Frequency Division Multiplexing Linear frequency modulation). Analyze the ambiguity function of OFDM-LFM orthogonal waveform to study the self-correlation and cross correlation property of it. In this study, OFDM-LFM orthogonal waveform shows nice orthogonality, higher resolution and larger Doppler tolerance.(3) Use minimum self-correlation side lobe peak value and cross correlation peak value as target function to develop orthogonal multiphase coding model. Design orthogonal multiphase coded MIMO radar waveform based on genetic algorithm, and its influence factors are evaluated.(4) The simulations about self-correlation and cross correlation properties of MIMO radar orthogonal waveform are carried out respectively to verify the validity and feasibility of waveform design. Orthogonal waveform shows a lower self-correlation side lobe peak value in self-correlation simulation experiment. Doppler frequency is also introduced to measure the influence of Doppler Effect on self-correlation. Cross correlation simulation experiment suggests orthogonal waveform has lower cross correlation peak value and variability influence factor value. It validates the correction of this research.According to the design criteria of orthogonal waveform, two kinds of orthogonal waveforms design are developed in this article, OFDM-LFM orthogonal waveform and orthogonal multiphase coded waveforms based on Genetic Algorithms. The simulation experiment shows that the autocorrelation side lobe peak value and cross-correlation peak value of both orthogonal waves have achieved the design requirements. OFDM-LFM orthogonal waveform is suitable for radar searching, and the orthogonal polyphase coded waveforms is more appropriate for the cases with small variation of Doppler that need high precision, such as tracking radar with the low velocity and so on. |
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