This work, for the first time to our best knowledge, presents a W-band multi-channel frequency-modulated continuous-wave (FMCW) radar system on low-cost FR-4 substrates. A center-fed patch array antenna on an FR-4 substrate can achieve a maximum gain of 10.8 dBi. It is enabled by aperture coupled feeding using an on-chip feeder implemented on a CMOS radar transmitter (Tx) and receiver (Rx). The proposed radar system consists of one Tx and four Rx channels placed in the back cavity of a microstrip array antenna like an active array antenna system. Additionally, Tx and Rx chipsets include a wideband frequency multiplier with high multiplication ratio of 63, making it easy to distribute reference FMCW waveform synthesized at a very low frequency about 1.25 GHz for 79 GHz output using direct digital synthesis (DDS). Extending the number of channels and implementing various waveforms can be easily accomplished with very good phase noise. The functionality of the proposed radar system on low-cost substrates is confirmed by distance and angle measurements.

This paper proposes a signal processing technique that recognizes hand motions using a 60-GHz frequency-modulated continuouswave radar system. In the case of hand motion recognition with a radar, the recognition accuracy decreases owing to a clutter signal generated by the upper body and differences between the hand sizes of different people. To solve this problem, this paper proposes a moving target indicator filter with a weighted frequency for each frequency, which improves hand motion recognition accuracy, removes self-interference clutter signals, and uses a range profile and Doppler profile. Neural networks can recognize hand movements; hence, the proposed five hand gesture recognition techniques exhibited an 87.3% accuracy, regardless of the user.

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