A coherent low IF receiver architecture for Doppler radar motion detector used in life signs monitoring

Continuous Wave Doppler radar has been used in human life signs monitoring from a distance. Such systems are basically motion detectors that rely on phase modulation of the radar´s reflected signal due to physiological motion which is of a low frequency nature and has significant signal content close to DC. Homodyne receiver architecture is simple, but has its own limitations including DC offset and contribution of low frequency noise from mixers and baseband amplifiers. A coherent low IF architecture has been proposed for this case to improve the performance. It will be shown that SNR is improved using a simple coherent low IF configuration. This is the first reported coherent low IF transceiver architecture for Doppler radar motion sensing.