基于FPGA 超声信号数字动态滤波器的实现

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。

Implementation of Ultrasound Signal Dynamic Digital Filter Based On FPGA

Objective: This paper talks about implementation methods and processes of digital dynamic filter based on Field Pro-grammable Gate Array(FPGA) in the ultrasound imaging system.Methods: In this paper finite impulse response(FIR) filter using dis-tributed arithmetic(DA) implementation structure and in the application of the DA algorithm we do some improvement including the structure of parallel data processing,controlling the size of the input word length N in the Look-Up Table(LUT) and using the FIR filter with symmetric coefficients.The structure improved can achieves balance between processing speed and occupation in the FPGA re-sources,at the same time,the FIR filter with pipeline structure can process digital ultrasonic signal in parallel way.Results: The resolution of ultrasonic echo image in the Far-field is satisfied using the constant coefficient filter(the parameters of filter in the far-field).However,as closer to the near field,worse the effect of the image is.In contrast,the digital dynamic filter based on FPGA can achieve a good filter-ing effect,so the images of the ultrasonic echo have the best resolution in the near-filed and the far-field.Conclusions: The implementa-tion of digital dynamic filter based on FPGA in the ultrasonic systems is entirely feasible,and it’s helpful for improving the system stability and reliability.