Quadrature Sampling of the Wireless Surface Acoustic Wave Sensor Signals

The delay time represents the variations of some parameter measured in delay-line type of the SAW sensors, so the precise extraction of the delay information from the reflected wave is the key in the process. In order to improve the sensitivity and resolution of wireless SAW sensor,the method of quadrature coherent detection which is based on the poly-phase filtering was used to process the signals of reflected wave. The results of both the simulation and experiment demonstrate that this quadrature sampling method can greatly reduce the error of the measuring system and also make the system easy to implement. In the end, the hardware of the system was given.