Optimized Time-Frequency Allocation in MIMO NU-OTFS Radar for Enhanced Performance Under Spectral Constraints

The performance of MIMO non-uniform orthogonal time-frequency space (NU-OTFS) radar with a high number of transmitters and limited spectral and temporal availability is investigated. NU-OTFS enables the implementation of OTFS communications with quasi-arbitrary distribution of time and frequency resources, increasing the usability of OTFS in spectrally congested scenarios. Moreover, the non-uniform sampling of time and frequency is beneficial for radar performance, as no decrease in resolution or unambiguous parameter estimation occurs. However, radar performance is dependent on the specific time-frequency sampling pattern. This work proposes an optimization framework based on the sidelobe level minimization of the joint ambiguity function of all the operating transmitters. Results show that a substantial sidelobe cancellation can be achieved with specific time-frequency patterns, resulting in viable radar systems with many transmitters in low spectral and temporal availability scenarios.