Measurements of cardiac and cardiopulmonary activities using contactless Doppler radar

This paper presents a wireless measurement system for cardiopulmonary activity. This system generates a continuous wave signal at 2.4 GHz toward the target and then measures the reflected signal. The target is the person´s chest set at a distance of 1 m. The radar system contains a vector network analyzer, which measures the phase of S₂₁. The phase variation of S₂₁ contains information about heart and respiration activity. Measurements are performed with two different conditions, while the person is holding respiration for 10 seconds and then breathing normally for the same duration. Filtering is used as processing technique to separate heartbeat signal from respiratory signal in the second case. The measurements were performed simultaneously with a PC-based electrocardiograph which is used as a reference to validate the information extracted from the measured signals.