Patent ID: 9100025
Filing Date: 2015-08-04
Classification: B82Y,G01G,G01N,H03B,H03L

Abstract:
1. A measurement circuit for measuring the oscillation frequency of a resonator, said circuit including an excitation input for receiving an actuation signal at a frequency close to a resonant frequency of the resonator and a polarization input for receiving a polarization signal comprising an AC component at a polarization frequency f1, the circuit including a phase-locked loop comprising the resonator, a frequency-controlled oscillator, and a phase comparator, wherein said polarisation frequency is applied by the frequency-controlled oscillator to said polarization input of the resonator, and wherein the circuit furthermore comprises a frequency generator supplying a fixed intermediate frequency FI, a mixer for mixing the intermediate frequency and the polarization frequency f1 and having an output for supplying an excitation frequency f0 that is the sum or difference of f1 and FI and for applying this excitation frequency f0 to the excitation input as actuation signal, the phase comparator receiving the intermediate frequency FI from the generator and a filtered output signal coming from the resonator, and supplying a locking signal to the frequency-controlled oscillator for controlling the polarization frequency f1 of the oscillator in a direction tending to maintain the excitation frequency at the output of the mixer at the value of the resonant frequency of the resonator.