Human Heartbeat Detection by Doppler Radar and Non Linear Tag

In this paper the detection of human heartbeat by Doppler radar was demonstrated in simulation. The targeted person wore the nonlinear tag that received two continuous wave fundamental signals separated in frequencies by 1 kHz. The nonlinear tag reflected toward the Doppler radar two received fundamental signals as well as the generated third-order intermodulation products. Mixed with the coherent local oscillator operating at one of fundamental signal frequency, the received signals were downconverted to the IF range, filtered, and processed by an exponential function of 2 kHz frequency. The baseband signal obtained in this manner contains information about the person's heartbeat that may be extracted by further adequate digital processing.