Research On High Frequency Oscillating Circuit For SAW Sensors

Due to the unique advantages such as small dimension, high sensitivity, stability, low cost, easy integrated, and wireless available, etc. The surface acoustic wave(SAW) sensors have been more and more applied for temperature, pressure, acceleration, humidity, and chemicals measuring.The SAW velocity change with the parameters of measured targets, and there will be some changes of the frequency, amplitude, or phase of SAW sensors after sensing. Detecting these changes, the target parameters can be accurately got. The stable behavior in RF frequency for SAW sensors is an important factor on the performance of the SAW sensor system.In view of the frequency characteristics of SAW sensors, the SAW sensor oscillating circuit has been studied and designed in this research.The applications of SAW sensors are different because of the different structures of SAW Devices. The SAW delay lines are mainly applied for chemical sensors, and SAW resonators are mainly applied for physical sensors. This research designed several oscillating circuits for SAW delay line, SAW filter, and SAW resonator respectively with Harmonic Balance Simulation by Advanced Design System(ADS). The simulation of the oscillation frequency and its harmonics power spectrum are made and analyzed. Finally, the real circuit system was made, tested and analyzed.When the sensor works in the electromagnetic environment, the electromagnetic wave will lower its SNR, which will affect the sensors' sensitivity, and lead to inaccurate measurement. It is same for SAW sensors. So the Computer Simulation Technology's 3D electromagnetic simulation software of CST STUDIO SUITE is applied to simulate and design metal shield of the dual channel SAW sensors oscillating circuit. Through the simulation analysis, the influences of gap, hole, material, thickness, and PCB parameters for shielding effectiveness are studied on, then the metal shield was designed and its shielding efficiency is predicted. The simulations give us many key points for the design.This is only one part of the study of SAW sensor system, and this research of SAW sensor oscillating circuit and electromagnetic shielding shell will contribute to the further research of SAW sensor system.