A Two-Tone Radar Sensor for Concurrent Detection of Absolute Distance and Relative Movement for Gesture Sensing

This letter presents a two-tone radar sensor system that can concurrently detect both absolute distance and relative movement. In contrast to the traditional two-tone radar, the proposed radar sensor can measure both distance and vibration. Moreover, it is more accurate in predicting the phase shift by leveraging the accuracy of nonlinear phase demodulation in the digital domain. Unlike the frequency-modulated continuous wave radar, the proposed radar system has simpler system architecture and does not require broadband signals. With a tone difference of 40MHz, the radar system can detect a distance up to 1.875m without ambiguity. Experiments show that the proposed radar system was able to not only capture the delaying movement of a Newton's cradle but to measure the distance with mm accuracy as well. It successfully detected the gesture motion of virtual slider, making it promising for sensing action gestures for human-computer interaction.