Doppler-compensated Space-time Coding for MIMO PMCW Radar

Phase modulated continuous wave (PMCW) radar is an attractive choice for automotive sensing due to its high dynamic range, interference robustness, and support for integrated communication and sensing. In multiple-input multiple-output (MIMO) PMCW radar, code division multiplexing (CDM) separates transmit signals, but non-ideal auto- and cross-correlation properties increase range sidelobes and degrade dynamic range. This paper proposes a Doppler-compensated space-time coding (STC)-based MIMO PMCW radar framework that separates transmit signals before range correlation, eliminating cross-correlation terms under perfect compensation and allowing the same binary sequence to be used across transmit antennas. The Doppler influence on STC decoding is analytically characterized, showing that chip-wise and inter-STC-slot phase distortions increase range sidelobes and generate ghost components in the direction-of-arrival (DOA) spectrum. To mitigate these effects, Doppler is estimated first, followed by joint fast-time and STC-slot compensation before decoding. Residual STC leakage under imperfect Doppler estimation is quantified, and the processing is extended to multiple moving targets through Doppler-bin-dependent compensation. Theoretical analysis and simulation results demonstrate reduced range sidelobes and suppression of DOA ghosts, while maintaining flexibility in code sequence design.