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 singlechannel 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.
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