Bandpass Sigma–Delta Modulator Employing SAW Resonator as Loop Filter

Abstract

Continuous-time bandpass (BP) sigma-delta modulators (61Ms) employing surface acoustic wave (SAW) resonators as loop filters are presented. Compared with the loop filters realized with -and LC resonators, the SAW resonator has the advantage of high-factor, wide resonant frequency range and accurate resonant frequency without the need for automatic tuning. With the proposed anti-resonance cancellation and loop filter phase compensation techniques, a second-and a fourth-order BP 61Ms are demonstrated in a 0.35-m CMOS technology. Both modulators are tested with 47.3-MHz off-chip SAW resonators. The second-order modulator attains a dynamic range of 57 dB and peak signal-to-noise distortion ratio (SNDR) of 54 dB and the fourth-order one achieves a dynamic range of 69 dB and peak SNDR of 66 dB, both in a 200-kHz signal bandwidth. The fourth-order modulator is also measured in a 3.84-MHz signal bandwidth and achieves a dynamic range of 52.5 dB and peak SNDR of 50 dB, an effective 8-bit resolution.Index Terms-Analog-to-digital converter (ADC), sigma-delta modulator (61M), bandpass (BP), surface acoustic wave (SAW) resonator.

Design of electronic control circuit of piezo-electric resonators for ΣΔ modulator loop in AMS Bi-CMOS 0.35µm

“…Accurate resonators with high Q-factor can be implemented by piezo-electric resonators like Surface Acoustic Wave (SAW) [2] resonators, Bulk Acoustic Wave (BAW) resonators [7] and Lamb Wave Resonators (LWR) [8]. In general, the model of Fig.3 is used to model a piezo-electric resonator around its fundamental resonance frequency.…”

“…Although CT modulators are good candidates when low-power, high-speed and small-size are of critical importance [2], they are highly sensitive to the performance of analog components [3]. One of the most important components is the resonator.…”

Electromechanical-Filter-Based Bandpass Sigma–Delta Modulator

“…Two prototype second-order BP ΣΔMs employing electromechanical resonators as loop filters, including both microelectromechanical system (MEMS) and surface acoustic wave (SAW) resonators, have been reported, but they are only suit- able for narrowband applications [7]- [9]. In this brief, a BP ΣΔM employing a single electromechanical filter with a large bandwidth is proposed.…”

Band-pass continuous-time delta-sigma modulators employing LWR resonators

“…Consequently it is still difficult to achieve high accuracy, especially in the case of narrowband digitization [2]. In order to improve the actual performance of the CT delta-sigma modulator, the need of an accurate resonator with high-Q factor is critical.…”