Design And Implementation Of Null Point Free VSD Radar Sensor Based On Rf Phase Shift

Vital Sign Detection (VSD) radar sensor is a non-contact detection system based on theory of Doppler Shift. Compared with other VSD detection system, VSD radar sensor has the advantage of good penetration and less constraint of detected objects, becoming widely used in health care, medical treatment and disaster rescue with broad market prospects.In this thesis, the research background and development of VSD radar sensor are presented firstly. After the analysis of the principle of traditional VSD radar system and the existing null point problem, a solution of introducing a radio frequency (RF) phase shifter is presented to solve it. Then, a VSD radar system of heterodyne direct intermediate frequency sampling architecture is set up rapidly with the RF instruments, which are widely equipped in the RF and Microwave laboratories. The result of experiment demonstrated that detection system can avoid the null point and get a better performance by introducing a RF phase shifter. Finally, a null point free VSD radar sensor is designed and implemented, which consists of the transmitter and the RF front-end of the receiver of the VSD radar sensor, as well as with the communication interface circuit between personal computer and the VSD radar sensor. The implemented circuit boards are debugged and analyzed according to the key performance indicator of the transceiver.Theoretical analysis and experimental result demonstrate that the introduction of RF phase shift to the VSD radar system which the null point problem exists in allows the radar system to avoid the null point, and lock the radar system detecting at optimal point, which result in a significant improvement in detection accuracy. Null point free VSD radar system has a good potential application in better detection accuracy, simpler architecture and more robust detection occasion.