Novel Approach for Vibration Detection Using Indented Radar

Non-contact vibration detection using microwave radar is becoming a popular research area. However, vibration sensing using Doppler radar based measurements suffers from the problem of ‘Null point’. In order to mitigate this, traditional designs incorporate phase measurements using Quadrature (I/Q) radar. Such Quadrature radars are not cost effective for large scale indoor deployment scenarios. In this paper, we propose a new configuration of ‘Indented Radar’; a system of two single-channel radars offset in space by a path length, which is equivalent to 90 degree phase shift. However, such a system of two independent channels is prone to different imbalances such as amplitude, phase and DC. This work closely examines the imbalance effect on the two-radar system and reports a novel approach that can be used to tackle such imbalance in a two-radar configuration. Our approach yields superior results over other commonly used I/Q algorithms, while measuring vibrational frequencies. Thus, our work can find immense application in both vital sign detection and structural vibration detection use-cases where affordable solution is sought.