Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus.
IEEE Trans Ultrason Ferroelectr Freq Control. 2011 Jul;58(7):1320-31. doi: 10.1109/TUFFC.2011.1952.
This paper describes the design of a programmable transmit beamformer application-specific integrated circuit (ASIC) with 8 channels for ultrasound imaging systems. The system uses a 20-MHz reference clock. A digital delay-locked loop (DLL) was designed with 50 variable delay elements, each of which provides a clock with different phase from a single reference. Two phase detectors compare the phase difference of the reference clock with the feedback clock, adjusting the delay of the delay elements to bring the feedback clock signal in phase with the reference clock signal. Two independent control voltages for the delay elements ensure that the mark space ratio of the pulses remain at 50%. By combining a 10- bit asynchronous counter with the delays from the DLL, each channel can be programmed to give a maximum time delay of 51 μs with 1 ns resolution. It can also give bursts of up to 64 pulses. Finally, for a single pulse, it can adjust the pulse width between 9 ns and 100 ns by controlling the current flowing through a capacitor in a one-shot circuit, for use with 40-MHz and 5-MHz transducers, respectively.
本文描述了一种用于超声成像系统的 8 通道可编程发射波束形成器专用集成电路 (ASIC) 的设计。该系统使用 20MHz 参考时钟。设计了一个具有 50 个可变延迟元件的数字延迟锁定环 (DLL)，每个延迟元件提供一个与单个参考时钟具有不同相位的时钟。两个鉴相器比较参考时钟与反馈时钟的相位差，调整延迟元件的延迟以使反馈时钟信号与参考时钟信号同相。延迟元件的两个独立控制电压可确保脉冲的占空比保持在 50%。通过将 10 位异步计数器与 DLL 的延迟相结合，每个通道都可以编程，最大延迟时间为 51μs，分辨率为 1ns。它还可以产生多达 64 个脉冲的突发。最后，对于单个脉冲，可以通过控制单稳电路中流过电容器的电流来调整脉冲宽度在 9ns 到 100ns 之间，分别用于 40MHz 和 5MHz 换能器。
