MIMO Radar Transmit Beampattern Design Without Synthesising the Covariance Matrix

Compared to phased-array, multiple-input multiple- output (MIMO) radars provide more degrees-of-freedom (DOF) that can be exploited for improved spatial resolution, better parametric identifiability, lower sidelobe levels at the transmitter/receiver, and design variety of transmit beampatterns. The design of the transmit beampattern generally requires the waveforms to have arbitrary auto- and cross-correlation properties. The generation of such waveforms is a two-step complicated process. In the first step, a waveform covariance matrix is synthesized, which is a constrained optimization problem. In the second step, to realize this covariance matrix actual waveforms are designed, which is also a constrained optimization problem. Our proposed scheme converts this two-step constrained optimization problem into a one-step unconstrained optimization problem. In the proposed scheme, in contrast to synthesizing the covariance matrix for the desired beampattern, nT-independent finite-alphabet constant-envelope waveforms are generated and preprocessed, with weight matrix W, before transmitting from the antennas. In this work, two weight matrices are proposed that can be easily optimized for the desired symmetric and nonsymmetric beampatterns and guarantee equal average power transmission from each antenna. Simulation results validate our claims.