A wide-band 280-MHz four-path time-interleaved bandpass sigma-delta modulator

Abstract

This paper describes a 0.35-/spl mu/m CMOS fourth-order bandpass analog-digital sigma-delta (/spl Sigma//spl Delta/) modulator for wide-band base stations receivers. The modulator, based on a time-interleaved four-path architecture, achieves an equivalent sampling frequency of 280 MHz, although the building blocks operate at only 70 MHz. In measurements, the prototype chip achieves a dynamic range of 72 dB (12 bits of resolution) with a signal bandwidth of 4.375 MHz centered around an intermediate frequency of 70 MHz. The measured spurious-free dynamic range is 69 dB. The /spl Sigma//spl Delta/ modulator dissipates 480 mW from a 3.3-V supply, including voltage reference buffers and output pads with high-driving capabilities, and occupies 20 mm/sup 2/ of silicon area.