In the embodiment of FIG. 8D, transmit and receive circuitry 112d includes amplifiers 834, 835, 838, 842, and 866, frequency mixer 840, and frequency dividers 864, and 856, 857, and 858. Relative to the transmit and receive circuitry 112c of FIG. 8C, transmit and receive circuitry 112d does not include frequency multiplier 836 because the waveform generator 110d generates microwave RF signals having a center frequency of 120 GHz (unlike waveform generator 110c that generates microwave RF signals having a center frequency of 60 GHz, which needs to be increased by a factor of two prior to being mixed with RF signals received by receive antenna 16 that is configured to transmit RF signals having a center frequency of 120 GHz). RF signals having a center frequency of 120 GHz and amplified by amplifier 834 are provided to frequency divider 864 to obtain RF signals having a center frequency of 60 GHz, which signals are: (1) transmitted by transmit antenna 14 after amplification by amplifiers 866 and 834; and (2) fed back to waveform generator 110d via the series of frequency dividers 856, 857, and 858 to provide RF signals having a center frequency of 7.5 GHz, which are provided via line 862 to chirp PLL circuitry 826 thereby providing a feedback loop. Accordingly, in the embodiment of FIG. 8D, the feedback loop includes line 861, amplifiers 854 and 834, frequency dividers 856-858 and 864, and line 862.
