Feasibility of heartbeat detection behind a wall using CW Doppler radar

This paper presents a wireless measurement system for cardiopulmonary activity detection behind a wall. This system generates a continuous wave signal and is used at 2 different frequencies: 2.4 GHz and 10 GHz. The transmitted signal is directed toward the patient's chest situated at 1 m and then reflected. The radar system is based on a vector network analyzer, which measures the phase of S21. The phase variation of S21 contains information about heart and respiration activity. Measurements are carried out every 30 seconds, for a person sitting at a distance of 1 meter, directly in front of the system or behind a wall. Discrete wavelet transform is used as a processing technique to separate heartbeat signal from respiratory signal. The measurements were performed simultaneously with a PC-based electrocardiogram (ECG) which is used as a reference to validate the information extracted from the measured signals.