Comparison between single and two-antenna VNA system used for heartbeat rate extraction

Abstract

Abstract-This paper presents a microwave system for measuring the cardiopulmonary activity performed in two ways: by using single antenna and by using two antennas. This system generates a continuous wave signal at 20 GHz toward the target and then measure the reflected signal. The target is the person's chest set placed at a distance of 1 m. The VNA measures the phase variation between the emitted and received signals. This phase variation contains information about the movement of the chest. An electrocardiograph is used simultaneously with the system as reference in order to determine the accuracy of the VNA system. The measurements are performed for a person under two conditions: breathing normally and holding the breath. Wavelet transform is used for the processing the obtained signals and the heartbeat rate is extracted accurately.