Pipeline analog -to -digital conversion for three -dimensional ultrasound imaging

Real-time three-dimensional (3-D) ultrasound imaging for medical and underwater applications is an area of expanding research interest. The realization of a real-time 3-D ultrasound imaging system mainly depends on the fabrication of phased two-dimensional transducer arrays with individually addressable elements, integrated with supporting signal-conditioning, control, and high-speed data acquisition circuitries. The implementation of the analog-to-digital (A/D) interface as an integral part of the imaging array decreases the sensitivity of the system to analog circuit imperfections and eliminates the need for an unmanageable number of interconnects between the ultrasonic probe and the processing unit. However, the constraints on the power dissipation and area of the A/D interface are often complicated by the need to process many wideband channels in parallel, to achieve high-quality imaging.;A novel 8-channel, 10-bit pipeline analog-to-digital converter is proposed for use in an integrated 3-D ultrasound imaging probe. The converter architecture combines multiplexing and pipelining to reduce the area and complexity of the embedded A/D interface. Two parallel sample-and-hold amplifiers are used to multiplex a total of 8 adjacent ultrasound channels, each operating at a 20 MHz conversion rate. The sampled and multiplexed signals are fed into two parallel pipeline paths operating at an 80 MHz sampling frequency. The two parallel pipelines are subsequently multiplexed into a single pipeline converter operating at 160 MHz to further conserve area. An experimental prototype of the proposed architecture implemented in a 0.25mum digital CMOS process occupies less than 4 mm2 of active silicon area and shows a peak signal-to-noise distortion ratio more than 54 dB for a 2.1-MHz input signal, while dissipating only 20 mW per analog input channel from a 2.5-V power supply.;The modular architecture allows integration of larger arrays as the area shrinks with technology scaling. The proposed architecture can also be used in other data acquisition and multi-sensor systems.