A band-pass delta-sigma modulator for ultrasound imaging at 160 MHz clock rate

A fourth-order band-pass delta-sigma modulator for ultrasound imaging is described. It is implemented in a 0.8-/spl mu/m BiCMOS process using switched capacitors. The signal band is centered at 5 MHz and is 2.5 MHz wide, where the modulator's dynamic range is 84 dB at a sampling rate of 160 MHz. Noise shaping can be programmed between band-reject and notch functions for B-mode (wide band) and CW-mode (narrow band) scanning, respectively.