Waveform Covariance Matrix Design to Enhance SINR in Collocated MIMO Radar: A Review and Comparative Performance Analysis

The most important issue in collocated multiple-input multiple-output (MIMO) radars is waveform design problem. This process usually is performed in two steps: designing a desired waveform covariance matrix and then generating a set of waveforms in order to realize this covariance matrix. Using conventional MIMO radars that transmit a set of orthogonal waveforms, results in achieving several advantages such as better parameter identifiability and interference suppression capability compared with the phased arrays. However, transmission of orthogonal waveforms yields a flat transmit beam-pattern which scatters transmit power uniformly in the space and results in significant SINR loss in the receiver. In order to exploit the advantages of both phased array and conventional MIMO radars, several methods have been proposed, recently. In this review article, at first, we have reviewed these methods and then, we have analyzed and compared these methods from three different aspects: a) transmit beam-pattern analysis, b) output SINR performance analysis by considering two scenarios (i.e. the directions of interferences are known or unknown), and c) interference suppression capability. Simulation results have showed several facts in order to have a guidance for performing future works.