Oscillator and frequency-shift measurement circuit topologies for micromachined resonant devices

Abstract

A circuit topology is proposed for using micromachined electrostatic/thermal resonators inside an oscillator loop. In this topology, the drive and sense signals are separated from each other in the frequency domain. Consequently, the circuit is significantly less sensitive to the parasitics. Moreover, the insertion losses from the input to the output of the resonator can be easily compensated by adjusting the gains of individual blocks inside the oscillator loop. A circuit design for tracking the changes of the resonant frequency of the signals is also presented. The frequency-shift measurement circuitry produces a voltage at its output which is proportional to the amount of change in the frequency of the input signal. This circuit can precisely detect small changes in the frequency of an input signal with large bandwidth. The topologies can be implemented using either integrated or discrete electronics and the experimental results have proven the viability of both circuits.