Instantaneous frequency extraction for resonant dew point sensor based on bandpass ΣΔ modulator with variable center frequency

Abstract

Aiming at the fast and accurate measurement of the output frequency of quartz resonant dew point sensor, there is developed a 1-bit fourth-order bandpass (BP) sigma-delta (ΣΔ) modulator to be applied in it. The automatic design and optimization have been both accomplished in the noise transfer function (NTF) and the architecture of 1-bit fourth-order bandpass (BP) sigma-delta (ΣΔ) modulator. It improved the design efficiency, variability of center frequency and signal-to-noise ratio (SNR) without stability problems compared to the traditional method. The variability of the center frequency is fully applicable to the measurement of quartz crystal resonators (QCR) with different base frequencies. Compare the general 14-bit modulator and the designed BP ΣΔ modulator in the frequency extraction, results show that the proposed method is more effective for fast frequency extraction of high frequency signals from QCR dew point sensor.