In this paper, we will describe the development of a 228 GHz heterodyne radar system as a vital signs sensing monitor
that can remotely measure respiration and heart rates from distances of 1 to 50 meters. We will discuss the design of the
radar system along with several studies of its performance. The system includes the 228 GHz transmitter and heterodyne
receiver that are optically coupled to the same 6 inch optical mirror that is used to illuminate the subject under study.
Intermediate Frequency (IF) signal processing allows the system to track the phase of the reflected signal through I and
Q detection and phase unwrapping. The system monitors the displacement in real time, allowing various studies of its
performance to be made. We will review its successes by comparing the measured rates with a wireless health monitor
and also describe the challenges of the system.