High-frequency ultrasound array transducers using piezoelectric thin films on larger structures are being developed for high-resolution imaging systems. The increase in resolution is achieved by a simultaneous increase in operating frequency (30 MHz to about 1 GHz) and close coupling of the electronic circuitry. Two different processing methods were explored to fabricate array transducers. In one implementation, a xylophone bar transducer was prototyped, using thin film PbZr(0.52)Ti(0.48)O(3) (PZT) as the active piezoelectric layer. In the other, the piezoelectric transducer was prepared by mist deposition of PZT films over electroplated Ni posts. Because the PZT films are excited through the film thickness, the drive voltages of these transducers are low, and close coupling of the electronic circuitry is possible. A complementary metal-oxidesemiconductor (CMOS) transceiver chip for a 16-element array was fabricated in 0.35-microm process technology. The ultrasound front-end chip contains beam-forming electronics, receiver circuitry, and analog-to-digital converters with 3-Kbyte on-chip buffer memory.
Our data suggest the presence of residual sensory integration dysfunction in concussed individuals at least 30 days postinjury and may indicate a lower threshold for brain reinjury.
The proposed CMOS ultrasound transceiver chip will enable the development of portable high resolution, high-frequency ultrasonic imaging systems. The transceiver chip is designed for close-coupled MEMS transducer arrays which operate with a 3.3-V power supply. In addition, a transmit digital beamforming system architecture is supported in this work. A prototype chip containing 16 receive and transmit channels with preamplifiers, time-gain compensation amplifiers, a multiplexed analog-to-digital converter with 3 kB of on-chip SRAM, and 50-MHz resolution time delayed excitation pulse generators has been fabricated. By utilizing a shared A/D converter architecture, the number of A/D converter and SRAM is cut down to one, unlike typical digital beamforming systems which need 16 A/D converters for 16 receive channels. The chip was fabricated in a 0.35-mum standard CMOS process. The chip size is 10 mm(2), and its average power consumption in receive mode is approximately 270 mW with a 3.3-V power supply. The transceiver chip specifications and designs are described, as well as measured results of each transceiver component and initial pulse-echo experimental results are presented.
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