Orthogonal Waveform Design For MIMO Radar

Multiple-input Multiple-output (MIMO) radar is a noval kind of radar system,which is characterized by transmitting different waveforms via its transmit ante nnas toimprove radar performances. According to the distance between radar antennas, MIMOradar is generally categorized into two kind, MIMO radar with colocated antennas andthat with widely separated antennas. The former has closely spaced antennas and canimprove degrees of freedom and angular resolution with the same number of antennas;the later has widely separated antennas can improve radar detection performance byusing the spatial scattering diversity of radar targets. For both kinds of MIMO radar, it iscritical to design radar waveforms of a low orthogonality in order to reap its claimedadvantages. The orthogonality of radar waveform includes two aspects-one is the mutalorthogonality, i.e., radar waveforms should mutually orthogonal, and the other is theself-orthogonality, i.e., radar waveforms should have low sidelobe levels. Thisdissertation focuses on orthogonal waveform design problem for MIMO radar based onoptimization methods. The main content of this dissertation is summarized as follows.1) The principles and characteristics of MIMO radar are studied and analyzed. Andthe basic idea of orthogonal waveforms and design criteria are also given.2）The genetic algorithms and the convex optimization theory are described, theoptimization process for genetic algorithms and the model for convex optimization aregiven as well.3）The methods to design orthogonal polyphase codes are investigated. Geneticalgorithm (GA) is employed to optimize the orthogonal polyphase codes, based onwhichorthogonal polyphase coded waveforms with36phases, multi-phase waveformswith relaxed mainlobe constrain, and orthogonal multi-phase waveforms with randomphases are designed. Numerical experiments indicate that the GA algorithm can be usedto design orthogonal waveforms of a low peak sidelobe level and a low peak sidelobelevel, such that the signal selfcorrelation and mutual correlation can be improved.4）The optimal peak sidelobe level mismatched filter design problem is studied.Convex optimization is proposed to improve the performance of orthogonal waveforms.The simulation results show that can further improve the peak sibelobe level.