A Low-Distortion Fourth-Order Bandpass Sigma-Delta Modulator Using Double-Sampling Technique

Abstract

In this paper, a low-distortion fourth-order bandpass sigma-delta (ΣΔ) modulator is proposed based on a switched-capacitor resonator which employs double-sampling technique to relax the requirements for circuits and reduce opamp power consumption and chip area. The modulator is based on the low-distortion low pass ΣΔ modulator. The system level simulation results compare between the low-distortion architecture and the traditional one is given. The full differential circuit applying two-path technique is implemented with TSMC0.18µm CMOS process. It achieves a peak SNR (signal-to-noise ratio) of 85.9dB and DR (dynamic range) of 91dB with 200 kHz bandwidth centered at 20MHz which are better than the conventional bandpass ΣΔ modulator.