High-resolution single-snapshot DOA estimation in MIMO radar with colocated antennas

In this paper, a high-resolution subspace-based method is proposed for single-snapshot direction-of-arrival (DOA) estimation in multiple-input multiple-output (MIMO) radar. First, a `principal´ weight vector is designed for transmit beamforming to achieve a desired transmit power distribution, e.g., to focus the transmit power within certain desired spatial sector(s), while minimizing the out-of-sector power. Then, the designed weight vector is used to generate a population of `companion´ weight vectors of the same size and having the same transmit power distribution as that of the principal weight vector. Multiple transmit beams are formed using the companion weight vectors where an orthogonal waveform is transmitted over each beam. Matched-filtering the received single-snapshot data to the orthogonal transmitted waveforms yields a number of virtual data snapshots equal to the number of orthogonal waveforms. By properly choosing the number of waveforms, the virtual data snapshots are guaranteed to yield a full-rank sample covariance matrix, which enables application of high-resolution DOA estimation techniques. Simulation results demonstrate that the proposed method provides DOA estimation performance superior to that of traditional MIMO radar based MUSIC, the conventional (Bartlett) beamformer, and the spheroidal sequences based beamformer.