Low Signal-to-Noise Ratio Vital Sign Detection Based on Template Selection

Normal human heartbeat and respiratory signals are not steady sinusoidal signals and contain a multitude of harmonic components. The principle of vital sign detection using millimeter-wave radar is based on monitoring the chest cavity’s movements to obtain vital sign signals. Due to the amplitude of the respiratory signal being an order of magnitude higher than that of the heartbeat signal, the higher-order harmonics of the respiratory signal, particularly the second and third harmonics, which fall within the frequency range of the heartbeat signal, can easily overshadow it. This overlap creates difficulty in separating respiratory and cardiac signals using traditional methods. This paper proposes a heartbeat signal extraction method based on template selection, which extracts the heartbeat signal during respiratory pauses, suppresses the interference of respiratory harmonics, and experimentally validates the effectiveness of the method.