A DC-coupled biomedical radar sensor with analog DC offset calibration circuit

A common problem of biomedical radar sensors is the DC offset at the output of radar receiver front-end. In this paper, a DC-coupled Doppler radar sensor system with an analog DC offset calibration circuit is proposed. The calibration circuit can track the change of DC offset continuously, and automatically remove the offset on the fly or in a controlled manner. The proposed calibration circuit uses pure analog components and does not require any digital signal processing (DSP) or software configuration. Compared to existing digitized solutions, the proposed analog calibration technique has the advantage of low cost, low complexity, extremely small delay, and very high resolution. Experiment demonstrates that input signals with a wide range of input DC offset can be processed. Hence the dynamic range of the baseband variable gain amplifier (VGA) can be maximized. Furthermore, the proposed DC offset calibration architecture can be easily adopted by other systems which also face DC offset problem.