Design And Implementation Of A RF Sensor With Single-channel Nonorthogonal IQ Signals For Movements Detection

With the advent of medical big data age,new type of hardware devices which are applied to smart medical has been sprung up.Compared with traditional medical devices,these hard-ware devices have characteristics on real time transmitting,domiciliary and continuous.There are obviously advantages over acquiring big data.It is possible to prevent disease by daily life's big date by modern medicine such as diagnosis of cardiovascular disease by analyzing scoop type curve,relationship between blood pressure dropping at night and strokes,or even OSAS.Movement signal is the main factor of sleep analysis in medical.Quality of sleep will be reduced because of frequent movements and our sleep will be disturbed by that reason.In ad-dition,movements during normal sleep can be used for detecting sleep apnea.Muscle spasm also has a relationship with movement for newborns.A single-antenna system RF sensor was designed and implemented in this paper for non-contact detecting movement signal.There was a plan for demodulating nonorthogonality IQ signals through hardware design and the accuracy will be improved by this plan.Moreover,a phase sensitive detection project was also designed for improving the accuracy of the sen-sor.A patch Yagi antenna working at the frequency of 2.4GHz was designed in the paper.There are three wave-guiders in the antenna and the highest gain is 8.9dB.A modified Yagi antenna is also designed for the sensor with a highest gain of 8.2dB.In addition,both of the antennas have outstanding directivity.The circuits were integrated with the antenna into a PCB board for cost reduction.A series of experiment were implemented for verifying the function of the sensor.The current consumption of the sensor is 30mA to 40mA with 5V DC power supplying.The return loss of the sensor is equal to-22.78dB by the analyzing of network analyzer.The signals acquired by the sensor were analyzed through FFT and wavelet analysis.The consequences were that the respiration signal will be detected by the sensor at the distance of 50cm and the heart rat signal will be detected by the sensor at the distance of 20cm.