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目的:本文研究了基于现场可编程门阵列(Field Programmable Gate Array,FPGA)超声成像系统中数字动态滤波器的实现方法和过程。方法:动态滤波器中FIR滤波器采用分布式算法(Distributed Arithmetic,DA)实现结构,并在应用中对DA算法进行了改进,包括数据并行处理结构的设计、对查找表(Look Up Table,LUT)输入字长N大小的控制和具有对称系数的FIR滤波器的采用。改进后的DA实现在FPGA资源占用和处理速度之间达到了平衡。同时,结合多级流水线结构,动态滤波器实现了数字超声信号并行处理。结果:采用常值滤波器(远场匹配参数)进行滤波后,超声回波图像远场分辨率达到了要求,但越靠近近场效果越差。相比之下,本文设计的基于FPGA超声信号动态数字滤波器达到了很好的滤波效果,使回声图像近场和远场都有最佳分辨率。结论:利用FPGA实现超声系统中动态滤波器是完全可行的,并且有助于提高系统的稳定性和可靠性,并大大减低系统成本。
OBJECTIVE: This paper studies the method and process of digital dynamic filter based on Field Programmable Gate Array (FPGA) ultrasonic imaging system. Methods: The FIR filter in the dynamic filter is implemented by the distributed arithmetic (DA), and the DA algorithm is improved in the application. The structure of the data parallel processing is designed. The Look Up Table (LUT) ) Control of input word length N size and adoption of FIR filter with symmetrical coefficients. The improved DA implementation achieves a balance between FPGA resource utilization and processing speed. At the same time, combined with multi-stage pipeline structure, dynamic filter to achieve digital ultrasonic signal processing in parallel. Results: After filtering with a constant-value filter (far-field matching parameter), the far-field resolution of the ultrasound echo image meets the requirements, but the closer the effect to the near field is, the worse it is. In contrast, the dynamic digital filter based on FPGA ultrasonic signal designed in this paper has achieved a very good filtering effect, so that the best resolution of near-field and far-field of the echo image is obtained. Conclusion: Implementing dynamic filters in ultrasound systems using FPGAs is entirely viable and helps to improve system stability and reliability, as well as significantly reduce system costs.