声表面波滤波器衍射迭代补偿的改进算法

Improved iterative compensation method for diffraction in SAW filters

高性能声表面滤波器的邻频抑制要求达到60 dB以上,此时必须对衍射效应进行补偿.基于δ函数模型,对采用分裂指设计的变迹叉指换能器,通过迭代校正电极孔径大小的方法来改善声表面波滤波器阻带抑制.该算法采用简化的滤波器模型以减少运算复杂度,引入两个误差参数作为迭代补偿结束条件而无需尝试迭代次数.最后给出了一个实际的声表面波滤波器设计实例,用普通PC机不到一分钟便可完成整个设计过程.数值模拟表明,由衍射效应带来的频带恶化基本得到校正.

The sidelobes of a high-performance surface acoustic wave filter need to be designed to higher than 60dB, so it is necessary to compensate the diffraction. To achieve desired frequency response, the aperture size of split-finger interdigital transducer is corrected iteratively based on δ function model. The simplified frequency response model is applied to reduce computing time, and two error parameters is introduced to quit the iterative compensation automatically rather than trying iterative times before compensation. An example of the design of an actual filter is introduced at the end. The whole procedure takes no more than one minute on common personal computers, and the calculation results show that the impacts caused by diffraction are almost removed.