A tunable SC bandpass delta-sigma modulator with noise-coupled architecture

Abstract

This paper presents a switched-capacitor (SC) bandpass (BP) delta-sigma (ΣΔ) modulator for wideband applications. Quantization noise coupling technique for a BP ΣΔ ADC is proposed to effectively increase the order of the modulator noise transfer function by two. A double-sampling switched-capacitor tunable resonator implemented with a single opamp is used to reduce the power consumption, and also to provide the tunability for different applications. The BP ΣΔ modulator is designed for a 0.18μm CMOS technology, and Matlab and HSPICE simulation results are presented to demonstrate the design concept. It will be shown that the peak SNDR of the proposed 6th-order noise-coupled BP ΣΔ ADC is about 12 dB higher than that of the conventional 4th-order one without increasing the power consumption.