A Portable Doppler/FSK/FMCW Multi-mode Radar With Analog DC Offset Cancellation for Biomedical Applications

This paper presents an integrated portable multi-mode radar system incorporating Doppler, frequency-shift keying (FSK), and frequency-modulated continuous-wave (FMCW) modes with an analog DC offset baseband cancellation circuit. The proposed radar system can be used for various biomedical applications such as non-contact vital signs monitoring, fall detection, and human tracking. A common problem of biomedical radar sensors is the DC offset presented at the output of the mixer caused by hardware imperfection and reflections from nearby stationary objects. This leads to signal distortion, baseband amplifier saturation, and dynamic range reduction. Therefore, an analog DC offset cancellation circuit is integrated to automatically and continuously remove the DC offset before baseband amplification. Experiment results of different modes are reported to demonstrate the multi-functionality of the proposed radar.