Experimental Results for Angular Resolution Improvement in Slow-Time Phase-Coded FMCW MIMO Radars

Multiple-Input Multiple-Output (MIMO) radars provide improved angular diversity provided the employed waveforms are orthogonal both at transmit and receive. The use of Slow-Time Phase-Coded (ST-PC) Frequency Modulated Continuous Wave (FMCW) waveforms provides the inherent benefit of better Signal-to-Noise Ratio (SNR) as compared to their counterpart slow-time multiplexing techniques such as Time Division Multiplexing (TDM) FMCW waveforms. Accruing the benefits linked with ST-PC FMCW MIMO waveforms, this paper investigates the use of these waveforms for implementation on actual hardware. Initially, the mathematical signal model for a Slow-Time Phase-Coded (ST-PC) FMCW MIMO radar is derived where it is shown that proper decoding of received returns for moving targets requires phase compensation of induced doppler shifts. Only then, the received returns can be separated corresponding to each transmitter antenna without any residual phase distortions. As a result, accurate angle estimation of the moving targets can be carried out. This derived model was then tested on actual hardware in an open-air setup with actual road targets. Finally, the improvement in angular resolution for ST-PC FMCW MIMO radar was compared with the conventional SIMO spatial spectrum which was unable to locate certain targets.