A 2.4-GHz vital-sign sensor for noncontact healthcare monitoring

Abstract

This paper presents a 2.4-GHz vital-sign sensor for noncontact healthcare monitoring applications. The sensor consists of one VCO, two circulators, three Wilkinson power dividers, one 90° hybrid, two mixers, and two active band-pass filters. The sensor with the injection-locked VCO and the I/Q demodulator reduces system complexity and avoids the null detection points, respectively. Moreover, the sensor achieves a long sensing distance without the need of a low-noise amplifier or a power amplifier. Under total power consumption of 17.8 mW, experimental results demonstrate that vital-sign signals including respiration and heartbeat can be identified and detected correctly up to 80 cm away from the subject. Moreover, the errors of heartbeats are less than 4.9% compared to a contact device.

Keywords:

• Life detection system
• vital-sign signals
• sensors
• noncontact
• injection-locked
• I/Q demodulator
• Health care monitoring