Phase noise characterization of polymer coated-SAW gas sensors: implications for the performance of an oscillator circuit

Polymer coated surface acoustic wave (SAW) devices have demonstrated high vapor sensitivity and vapor class selectivity in detecting gases. The measurements are usually obtained as the output frequency of a loop oscillator circuit, which utilizes the polymer coated-SAW device as the feedback element. The sensitivity of the measurement system depends on the noise performance of the loop oscillator circuit. In this present work, we examine the quality factor and residual phase noise of polymer coated SAW devices and predict the theoretical limit of the phase noise performance of the loop oscillator