Sigma-Delta Solutions For Future Wireless Handhelds

This paper addresses the different issues in the design of ADCs for future wireless handhelds. It reviews the constraints imposed on the receiver design by the low-power specifications in handhelds. The sigma-delta ADC architectures that can potentially be used for implementing future wireless handhelds are discussed in the perspective of a CMOS implementation. Finally, a 4(th) order 4bit continuous-time bandpass sigma-delta modulator capable of digitizing a WiMAX (20MHz) signal band centered at an IF of 75 MHz is presented. The simulation results shown that the proposed sigma-delta modulator can provide a SNDR of 50.1 dB and a DR of 56 dB at a sampling frequency of 500 MHz.