Partially adaptive transmit beamforming for search free 2D DOA estimation in MIMO radar

In this paper, a partially adaptive two dimensional (2D) trans mit beamforming approach is proposed to enable search-free azimuth and elevation direction of arrival (DOA) estimation in MIMO radar. Specifically, the 2D transmit array is non-adaptively partitioned into a number of subarrays. Then, a beamspace matrix is adaptively designed for each subarray, such that the beampatterns corresponding to each matrix have the exact same magnitude. By constraining the beams to be transmitted from different subarrays, multiple data in variances are enforced independently of the receive array geometry. The invariances are then exploited by search-free DOA estimation methods. Simulations validate the proposed approach.