A 12mW low-power continuous-time bandpass ΔΣ modulator with 58dB SNDR and 24MHz bandwidth at 200MHz IF

Abstract

A continuous-time bandpass ΔΣ modulator (CTBPDSM) is a good solution for software-defined-radio (SDR) since it allows much flexibility in the digital backend and also decreases the complexity of the receiver chain by combining several analog blocks into a single ADC [1]. However, conventional CTBPDSMs suffer from large power consumption and occupy large area. CTBPDSMs based on LC tanks are large, while biquad-based resonators are also large and suffer from high power consumption because two amplifiers are usually required in each resonator. The fact that there are typically twice as many feedback paths compared to a lowpass ΔΣ modulator with the same bandwidth and performance also increases power consumption, area and complexity. This paper presents a power-efficient resonator with a single amplifier and also introduces a simplified architecture utilizing return-to-zero (RZ) and half-clock-delayed return-to-zero (HZ) pulses to solve the power and complexity problems.