Remote sensing of vital signs based on Doppler radar and Zigbee interface

This paper proposes to remote sense vital signs by means of a Doppler radar based on phase diversity to overcome null detection. The system uses two channels in reception with a convenient phase-shift between them in order to ensure proper detection. A switch controlled by software selects the channel with larger amplitude. In addition, the system uses Zigbee as air interface in order to be able to have the microwave sensor far away from the control PC or processing center. The Zigbee system acquires, modulates and transmits the signal via RF, and also transmits the control orders from the control program to the radar for selecting the switch position.