An A/D Converter for Multimode Wireless Receivers, Based on the Cascade of a Double-Sampling$SigmaDelta$Modulator and a Flash Converter

This work proposes an architecture for an analog-to-digital converter intended for a multimode wireless receiver. The architecture is based on the cascade of a single-bit 2-1 sigma–delta modulator and a 4-bit flash converter. Furthermore such an architecture is mapped in a modular implementation, which allows to easily reconfigure modulator order, oversampling ratio and equivalent number of bits of the internal quantizer. As a consequence, the proposed converter can fulfill the requirement of a wide range of standards: Global System for Mobile Communications (GSM), Bluetooth, universal mobile telecommunications system (UMTS), and wireless local area network (WLAN)a. The paper discusses extensively the effects of circuit nonidealities on the converter performance, in order to single out the most suited setup for the programmable parameters and to demonstrate the practical feasibility of the proposed system. The converter figures of merit have been quantified by means of transistor-level and behavioral simulations: the achieved dynamic range is 85, 72, 62, and 59 dB for GSM, Bluetooth, UMTS, and WLANa, respectively. The corresponding power consumption is 4.6, 5.5, 7.4, and 18.9 mW.