A band pass /spl Sigma//spl Delta/ modulator for ultrasound imaging at 160 MHz clock rate

Abstract

Phased-array ultrasound imaging is a promising application for /spl Sigma//spl Delta/ converters, where overall analog hardware can be simplified in exchange for increased digital signal processing (DSP) complexity. A 4th-order band-pass modulator for this application in 0.8 /spl mu/m BiCMOS has a 2.5 MHz-wide signal band centered at 5 MHz. To meet system-level specifications, the modulators dynamic range is 84 dB, achieved by sampling at 160 MHz and performing 24 dB of time-gain-control in the modulator. Noise shaping is programmable between band-reject and notch functions for B-mode (wide band) and CW-mode (narrow band) scanning, respectively.