An Adaptative Ratio-Metric Analog-To-Digital Interface For Weakly-Coupled Resonant Sensors Based On Mutually Injection-Locked Oscillators

Abstract

In this paper, we propose a new ratio-metric interface for amplitude-modulated MEMS sensors based on mutually injection-locked oscillators (MILO). The two outputs are down-converted by a peak demodulator to improve the immunity to phase variation and noise. The peak values are then fed into a second-order discrete-time delta-sigma modulator that directly produces a digital ratio-metric output with a worstcase resolution greater than 16 bits and with input full scale of 0.6. The interface is clocked by the resonators output signal and is adapted for a sampling frequency up to 1MHz.

A highly-linear, integration-compatible output metric for amplitude-modulated resonant sensors based on weakly-coupled resonators

“…Similar results can be observed for other WCR architectures, such as those based on mode-localization. Finally, as shown in [11][12], the bilinear amplitude ratio is amenable to integration and high-resolution analog-to-digital conversion. Fig.…”

“…2. System-level representation of a ratiometric AM WCR with digital output consisting of an AM WCR, an analog amplitude demodulation block (sample-hold + lowpass filter) and a ratiometric ΣΔ converter [11][12]. The sampling frequency can be generated in the WCR (e.g.…”

“…Furthermore, from a practical perspective, it is possible to digitize ( ) from the amplitudes ( ) and ( ) without having to implement electronic blocks for the addition and subtraction of these quantities, or for the division. To this end, [11] proposes a continuous architecture of a "ratiometric" ΔΣ-ADC, a discrete-time version of which was proposed in our own work [12], as shown in Fig. 2.…”