Adaptive harmonics comb notch digital filter for measuring heart rate of laboratory rat using a 60-GHz radar

Harmonics of respiration frequency due to nonlinear Doppler phase demodulation may interfere the identification of heartbeat frequency in vital sign radar's baseband spectrum. The proposed adaptive harmonics comb notch digital filter is a type of spectrum-based filtering function with no degradation on the heartbeat signal, and no calibration is needed when the detection distance changes. Experimental results show that the proposed filter for removing respiration harmonics can help measuring laboratory rat's heart rate more accurately when the heartbeat movement is weak or overwhelmed by the respiratory movement in the detected spectrum. Furthermore, even when the heart rate is totally overlapped by the respiration rate harmonics, the heart rate can still be extracted.