||This thesis is devoted to extend self-injection locked (SIL) radar in life detector and wearable device.This system can remotely monitor the 1-D vibration, displacement, and range information of a moving target.|
In life detector part, to achieve this goal, an additional phase shifter which provides 0°/90° phase delay is utilized in the quadrature self-injection-locked (QSIL) radar architecture. With the corresponding digital signal processing techniques, the moving target’s Doppler phase shift can be determined without the nonlinear distortion caused by the SIL phenomenon. Then the range information can be figured out by the phase difference of the two demodulated signals that one respectively measured with two different carrier frequencies. In experiments with a prototype operated at 2.4 GHz ISM band, a metal plate controlled by a precise actuator is utilized to verify the theoretical predictions.Moreover, for an individual seated 1.75m away from the radar, the prototype can successfully detect the vital sign and range information based on the subject's tiny chest movement. Accordingly, in the premise of saving spectrum resource, it is demonstrated that the system has promising ability to detect vibration, displacement, and distance with high dynamic range from tiny fluctuation such as vital signs to general case such as motion detection and vibrometering.
In wearable device part,to achieve sensitivity, comfort, and durability in vital sign monitoring, this study explores the use of radar technologies in wearable devices. The study first detected the respiratory rates and heart rates of a subject at onemeter distance from the radars to compare the sensitivity versus power consumption between an SIL radar and a CW radar. Then, a pulse rate monitor was constructed based on a bistatic SIL radar architecture. This monitor uses an active antenna that is composed of a SIL oscillator (SILO) and a patch antenna. When attached to a band worn on the subject’s wrist, the active antenna can monitor the pulse on the subject’s wrist by frequency modulating the SILO with the Doppler phase shift. Subsequently, the SILO’s output signal is received and demodulated by a remote frequency discriminator to obtain the pulse rate information.