Comparative Analysis of Sinusoidal Oscillators with Surface Acoustic Wave Sensor in the Feedback Loop

Surface acoustic wave sensors can be implemented within the feedback loop of sinusoidal oscillators for detecting pollutants. This detection process involves analyzing the variation of oscillator output voltage parameters, such as amplitude and oscillation frequency. However, each oscillator topology has a distinct operating range concerning frequency and component values. Therefore, a comparative analysis is necessary to determine the oscillator with optimal performance to use with the sensor. To obtain results, a surface acoustic wave sensor model was chosen based on a piezoelectric crystal with a resonant frequency of 117.6 MHz, and three sinusoidal oscillator topologies were used: Pierce, Colpitts, and Clapp. The oscillators were simulated with the sensor model in the feedback loop using the Montecarlo method. The simulation occurred in two steps: individually varying each component by +/- 20% with 250 iterations, and simultaneously varying all components by +/- 20% with 1000 iterations. The variables analyzed in the simulations were amplitude, oscillation frequency, and a new parameter indicating the percentage of time there is an oscillation, termed "robustness." As a result, it was determined that all three oscillators generated oscillations in the output voltage, making them viable for use with the sensor. Furthermore, it was discovered that the Clapp oscillator had a robustness of 84.5%, while the Colpitts and Pierce oscillators had a robustness of 56.3% and 49.9%, respectively. Therefore, based on the results presented in this study, the Clapp oscillator is the optimal choice for use with the surface acoustic wave sensor.