Hybrid Continuous-Wave and Self-Injection-Locking Monopulse Radar for Posture and Fall Detection

This article presents a novel monopulse radar that combines high-sensitivity continuous-wave (CW) and self-injection-locking (SIL) receivers to detect and localize the movements in a human body. The proposed radar utilizes a CW sum pattern and an SIL difference pattern to process the echo signal from the target, so it can produce a monopulse ratio to estimate the angle of arrival (AoA) of the echo signal. With this capability, the radar can localize the movements on the target’s chest that are caused by vital signs such as respiration and heartbeat for posture classification. In addition, the radar can be used in a fall alarm as it can detect a change of posture during a fall. As a proof of concept, a 2.4-GHz prototype radar was experimentally implemented to validate the robustness of detecting falls regardless of their direction.