Modulation Scheme Impact on Phase Noise in FMCW Radar for Short-Range Applications

This paper presents an analysis of different modulations that can be used at low-IF in short-range frequency-modulated continuous wave (FMCW) radars which are more sensitive to DC offsets and flicker noise. These modulations are also a key functionality in multiple-input multiple-output (MIMO) FMCW radars to implement orthogonality between the different transmit signals. Architectures with two PLLs, set at slightly different frequencies to create a low-IF, and one PLL, using OOK and BPSK modulations, are compared regarding their phase noise at the resulting IF signal. Measurements were performed on a COTS 60 GHz FMCW radar to validate the calculated and simulated results.