||This thesis presents a non-contact radar system. This non-contact radar system uses wearable microstrip antenna in a single-frequency continuous-wave radar which operates concurrently with two different modes. The two different modes are: self-injection-locked CW mode (SIL mode) and range-correlated CW mode (RC CW mode). Then, the Labview software is used to collect the data and calculate the pulse transmit time.|
To conduct this experiment, three antennas are designed first. These three antennas are: rectangular microstrip antenna, loop microstrip antenna, and flexible antenna. These three antennas are used in the radar system to detect human’s pulse and heartbeats. Also, the influences of human body on the antenna are taken into consideration. Second, these three antennas are applied in the radar system, operating with two modes, ie, SIL mode and RC CW mode. The radar system utilizes a voltage control oscillator with injection port to transmit RF signal to wrist and chest antennas through the power splitter. The wrist antenna detects movement due to pulse and makes oscillator enter the SIL state. And thus, a frequency demodulator can be used to obtain the waveform of pulse. On the other hand, the chest antenna detects the movements due to heartbeats and then an IQ demodulator can be used to obtain the waveform of heartbeats.
Based on Biopac company’s pulse transit time measurement using electrocardiography and photolethysmography sensors, the results show that the peak time difference between the two resultant output signals in the radar system is closely correlated with the pulse transit time. Compared to other contact sensors, the presented wearable physiological monitoring radar system takes the advantages of low cost, convenience, and comfort.