Waag Robert C, Fedewa Russell J
Department of Electrical and Computer Engineering and Imaging Sciences, University of Rochester, Rochester, NY 14627, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2006 Oct;53(10):1707-18. doi: 10.1109/tuffc.2006.104.
An ultrasonic ring transducer system has been developed for experimental studies of scattering and imaging. The transducer consists of 2048 rectangular elements with a 2.5-MHz center frequency, a 67% -6 dB bandwidth, and a 0.23-mm pitch arranged in a 150-mm-diameter ring with a 25-mm elevation. At the center frequency, the element size is 0.30lambda x 42lambda and the pitch is 0.38lambda. The system has 128 parallel transmit channels, 16 parallel receive channels, a 2048:128 transmit multiplexer, a 2048:16 receive multiplexer, independently programmable transmit waveforms with 8-bit resolution, and receive amplifiers with time variable gain independently programmable over a 40-dB range. Receive signals are sampled at 20 MHz with 12-bit resolution. Arbitrary transmit and receive apertures can be synthesized. Calibration software minimizes system nonidealities caused by noncircularity of the ring and element-to-element response differences. Application software enables the system to be used by specification of high-level parameters in control files from which low-level hardware-dependent parameters are derived by specialized code. Use of the system is illustrated by producing focused and steered beams, synthesizing a spatially limited plane wave, measuring angular scattering, and forming b-scan images.
已开发出一种用于散射和成像实验研究的超声环形换能器系统。该换能器由2048个矩形元件组成，中心频率为2.5MHz，-6dB带宽为67%，间距为0.23mm，排列在直径为150mm、高度为25mm的环形中。在中心频率下，元件尺寸为0.30λ×42λ，间距为0.38λ。该系统具有128个并行发射通道、16个并行接收通道、一个2048:128发射多路复用器、一个2048:16接收多路复用器、具有8位分辨率的独立可编程发射波形以及在40dB范围内独立可编程的具有时变增益的接收放大器。接收信号以20MHz、12位分辨率进行采样。可以合成任意的发射和接收孔径。校准软件可将由环的非圆形度和元件间响应差异引起的系统非理想性降至最低。应用软件通过在控制文件中指定高级参数来使系统得以使用，低级硬件相关参数则由专用代码导出。通过产生聚焦和转向波束、合成空间受限平面波、测量角散射以及形成B扫描图像来说明该系统的使用情况。
