Recently, phase-modulated continuous-wave (PMCW) systems have been gaining attention as a next-generation waveform for autonomous driving systems due to their capability of integrated sensing and communication with high-resolution sensing ability. Because high-resolution PMCW radar systems require a wide array aperture and wide bandwidth, the severe range-angle coupling effect can degrade the sensing performance. To address this issue, we first formulate a signal model for PMCW radar systems that accounts for range-angle coupling, also referred to as the spatial-wideband effect, and classify this effect into range migration and beam squint. Based on the formulation, our analysis shows that PMCW radar systems are more vulnerable to range-angle coupling than frequency-modulated continuous-wave radar systems, which highlights the importance of the proposed mitigation technique. To mitigate the issue, we propose a novel range-angle decoupling method for PMCW radar systems that uses a modified correlation process. The simulation results show that the proposed method improves both the peak power and the half-power beam width of the target angle response, even in scenarios with multiple targets. Furthermore, the computational complexity of the proposed method is relaxed by Fourier transform-based interpolation, which enables significantly faster computation with negligible performance degradation.
