Five-Port Receiver for Vital Signs Detection

A novel RF circuit, specifically a five-port receiver (FPR) for vital signs detection is presented. The proposed receiver operates at 5.8 GHz with a continuous wave (CW) signal. The system, which operates as a doppler-RADAR, was simulated, fabricated, and characterized and measurements of respiration rate and heart rate are performed. The concept relies on the detection of the phase of the received signal which changes due to the physical movement of the chest and nearby biological tissues. This is performed with the FPR, the associated calibration, and the signal processing procedure. Accurate measurements of respiration and heartbeat frequency as well as their time domain waveforms are obtained. Additionally, a microstrip and a Vivaldi antenna were also used which helped achieve longer distance monitoring.