基于多级半带滤波器的超声相控阵聚焦延时

建立了基于多级半带滤波器的超声相控阵聚焦延时系统，以提高仪器延时精度。研究了聚焦延时原理与延时算法的实现。首先，采用内插滤波的方法，设计了半带滤波器作为内插滤波器；然后，对8倍内插结构进行了改进，通过多级半带内插滤波器合成技术，将合成后的滤波器分解为8个子滤波器进行同时滤波，使得内插与多相分解可同时进行。最后，通过对延时算法的仿真分析与现场可编程门阵列（FPGA）的实现，验证了此算法的可行性。实验结果表明：该系统在100 MHz采样率的条件下可实现1.25 ns延时精度，与同性能普通有限长单位冲激响应（FIR）内插滤波器相比，运算量最大可减少21.4%。此方案在运算量、计算速度、分辨率、性价比方面均具有较大优势，非常适合于实时性强、精度高的聚焦延时算法的实现。

Focusing time delay of ultrasonic phased array based on multistage half-band filter

An ultrasonic phased focusing time delay system was established by using the multi-stage half-band filters to improve the accuracy of ultrasonic phased array instruments. The principle of the focusing time delay and the realization of the corresponding time delay algorithm were investigated. Firstly, the interpolation filter with a half-band one was used as an interpolation filter based on interpolation method. Then, the structure of the 8 × interpolation was improved. With a synthesis technique of a multi-stage half-band interpolation filter, the synthesized filter was divided into 8 sub-filters to work at the same time. In this way, both interpolation and polyphase decomposition could be simultaneously processed. Finally, the feasibility of this delay algorithm was verified by using the simulation analysis and the implementation of Field Programming Gate array(FPGA). The experimental results show that the time delay accuracy of the system is 1.25 ns at a sampling rate of 100 MHz. Comparing with the ordinary Finite Impulse Response(FIR) interpolation filter, the amount of computation with proposed interpolation filter can be reduced by 21.4% under the same condition. The program is characterized by lower computation amount, fast computing speed, excellent resolution and cost efficiency and can improve the overall performance for phased array instruments.