Article from Rene’ Meadors, MPH, Marketing Associate, Office of Industry Engagement at Georgia Tech Research Corporation.
Although numerous wireless solutions have been developed for sensing vital sign information, the best discovered option appears to be a continuous-wave (CW) Doppler radar, which can easily reach a resolution of submillimeter and is suitable for vital sign detection. The Doppler radar transmits a microwave signal which is phase modulated by the chest surface displacement due to respiration and heartbeat, and the vital sign information is exhibited in the phase variation of microwave signal.
In the detection process, residual phase noise can contaminate the received wave, reducing the quality of the vital sign information. By reducing the phase noise, the radar can extract more accurate vital sign information, and also extend the detection range.
Researchers Ying Zhang and Zongyang Xia from the School of Electrical and Computer Engineering at Georgia Tech have developed and experimentally demonstrated the use of a non-contact vital sign detection system using phase locked loop (PLL) to automatically suppress the residual phase noise. A PLL is a negative feedback scheme that synchronizes the output signal with a reference. The designed dual-carrier system uses PLL to lock the phase of one carrier’s beat signal to a low-noise reference signal to suppress the residual phase noise, providing a clean transmission path for the other carrier.
This technology automatically adjusts the feedback signals to suppress the noise when the environment or application changes, and also detects heartbeat at 250 cm, more than twice the distance of the unlocked system. In addition, the noise level is reduced by the PLL, it has higher signal to noise ratio and longer detection distance. This technology can be used to detect vital signs in all four physical orientations, making it superior to current systems. This technology could be applied in several industries include healthcare, biomedical fitness monitoring, automotive seating, and search and rescue operations.
It has received the Tech Connect Innovation Award at the National Innovation Summit in May 2017, and will be featured at the Defense Innovation event in Tampa, Florida in October 2017.