4D-imaging mmWave radars offer high angular resolution in both azimuth and elevation, but achieving this requires a large antenna aperture size and a significant number of transmit and/or receive channels. This presents a challenge
for designing transmit waveforms that are both orthogonal
and separable on the receive side, as well as have low
auto-correlation sidelobes. This paper focuses on designing an orthogonal set of sequences for 4D-imaging radar sensors based on PMCW technology. We propose an iterative optimization framework based on Coordinate Descent, which considers the Regions Of Interest (ROI) and optimizes a phase-modulated constant modulus waveform set based on weighted integrated sidelobe level on the required ROI and spectrum shaping. The optimization also accounts for the radar working adjacent to communication systems and other radar sensors. Simulation results are provided to demonstrate the effectiveness of the proposed method, which achieves low sidelobe levels and is compatible with spectrum constraints
