Study On Beamforming For HF MIMO Radar With Frequency Diversity

Multiple-input multiple-output (MIMO) radar has attracted extensive attentionin recent years. High-frequency radar can provide over-the-horizon detection but onlyvery limited dispersed frequency resources can be used. Multi-carrier frequencytechnology can take advantage of the dispersed frequency resources, so MIMO radarwith frequency diversity (f-MIMO) can be applied to HF radar. In this article, beamforming technology of multi-carrier MIMO radar is studied. The main work of thethesis is as follows:1. Base on array signal model, multi-carrier signal is expounded and multi-carrier array signal model is established. The concept of virtual arrays of f-MIMOradar is analyzed in detail. Then conventional beam forming algorithm of f-MIMOradar is derived and simulation results show the beamforming performance ofdifferent sets of multi-carrier frequency signals.2. Particle swarm optimization (PSO) algorithm is applied to select the optimalcarrier frequency combination to achive the best sidelobe performance. For specificcarrier frequency combinations, we extract array elements from the virtual array toget the optimal sparse array structure, and the simplified physical receive arraystructure is proposed. Finally, to optimize side-lobe performance of multi-carriersignals with large frequency intervals, we use convex optimization theory to get theoptimal weights with which the resolution of the main lobe can be maintained.3. Impact of the multi-carrier frequency echo signals with different frequencyamplitude and phase on beamforming performance is analyzed, and the necessity ofrobust beamforming is proposed. Based on Capon beamforming algorithm, robustCapon algorithm and doubly constrained robust Capon algorithm are elaborated.Simulation results show that for multi-carrier signals, the robust Capon algorithm hasgood output SINR at low input SNR, and is insensitive to the angular error and samplesnapshots. Finally, targeted at the problem of unknown error and dense interferences,RAB-SDP-WC algorithm for f-MIMO radar is proposed. This algorithm sustains theresponse of specific region while minimizing the output power of the worst case.Compared to the R-SOCP algorithm, the proposed algorithm has better interferencesuppression capability and sidelobe performance.