Phase-based Doppler Disambiguation in TDM and BPM MIMO FMCW Radars

The Doppler disambiguation techniques in the Multiple-Input Multiple-Output state-of-the-art are usually benchmarked for simple modulation schemes such as Time Division Multiplexing (TDM). However, the functionality ensured in TDM does not necessarily extrapolate to other more complex modulation schemes such as Binary Phase Modulation (BPM), in which simultaneous phase codes are transmitted to increase the aperture size of the antenna array while keeping a higher signal-to-noise (SNR) ratio. One of the commonly applied Doppler disambiguation techniques for TDM, which is based on a hypothetical phase compensation (HPC) is presented in this paper through an extensive comparison between TDM and BPM. Our study describes its Doppler disambiguation dependency with the number of transmitters, and discloses vulnerabilities involved in applying the HPC technique to the two modulation schemes, by using synthetic scenarios generated with MATLAB, and real data collected with a 77 GHz frequency modulated continuous wave (FMCW) radar.