MIMO Radar Waveform Design for Wideband Beampattern with Conjugate Gradient Method on Manifold

Abstract

To tackle the scenario in which a Multiple-Input Multiple-Output (MIMO) radar operates in the presence of interference from other communication systems, this paper investigates wideband waveform design for MIMO radar to enhance beampattern synthesis in a spectrally crowded environment. First, the optimization problem is modeled by minimizing the mean squared error (MSE) for beampattern matching while controlling the energy over specific spatial-frequency spaces (SFSs) to reduce the interference to other systems. Due to the constant modulus (CM) constraint, the resulting problem is non-convex and difficult to handle with conventional optimization methods. Therefore, log-exponential smoothing is applied to construct an exact penalty reformulation of the constrained problem, which is then remodeled on the complex circle manifold and solved efficiently by the Riemannian conjugate gradient (RCG) method. Finally, numerical results show that the proposed method generates deeper nulls in the prescribed SFSs than the counterparts in different scenarios while preserving the beampattern matching accuracy, which demonstrates the superiority of the proposed method.