Dual channel surface acoustic wave (SAW) oscillators of two-port SAW resonators were designed for sensor application. A feedback loop were determined by measuring the corresponding open loop and adjusting the point of 0° total phase to exist near to the point of peak gain by variation of coupling inductance value. Two such feedback loops, a mixer and a TTL invertor comprise a dual channel SAW sensor oscillator. To achieve a stable oscillation, incorporation of a power conditioning components and the use of microstrip techniques (50 Ω characteristic impedance and the least inductance path for RF return currents) are necessary. The standard deviation of difference frequency stability of the oscillator of 433.92 MHz is about 3.92. Finally, the dual channel SAW sensor oscillator is used to detect dimehylmethylphosphonate (DMMP) vapor.
A modified spin coating method is utilized to prepare waveguide layers of Love Wave devices. The thickness of PMMA
waveguide layer up to 3.0 μm is obtained with a smooth surface. The properties of these sensors, such as, mass
sensitivity, insertion loss are studied as a function of layer thickness. Mass sensitivity up to 705cm2g-1 is demonstrated.