Codesign of constant modulus waveform and receive filters for FDA-MIMO radar

The joint design of waveform and receive filter is one of the important technologies currently being studied in Frequency diverse array multi-input multi-output (FDA-MIMO) radar. The problem model studied in this paper is to maximize the signal-to-interference-noise ratio (SINR) of the system under the constant modulus constraint of the waveform and the norm constraint of the filter. The problem is non-convex, which brings challenges to its solution. Existing methods use relaxation-based methods to solve this problem, but this will inevitably introduce relaxation errors. To solve the above problems, we notice that the complex circle-sphere manifold space (CCSMS) can naturally satisfy the constant modulus constraint and norm constraint. Based on this feature, the problem becomes an unconstrained optimization problem on the CCSMS manifold, eliminating the need for relaxation. The Riemannian conjugate gradient algorithm can then be directly applied to solve the waveform and receive filter in parallel. We compared it with the existing methods through simulation: 1) SINR was improved by $4\mathrm{dB}$; 2) the computational complexity was reduced compared with existing methods.