抽指加权宽带扇形叉指声表面波滤波器的等效电路分析

Analysis of wide-band slanted transducer SAW fiiters using withdrawal weighting by equivalent circuit model

扇形换能器可以看成若干个沿孔径方向划分的均匀孔径换能器电端并联而成,根据梅森(Ma-son)等效电路模型以及由其延伸的混合场等效电路模型,推导出整个扇形换能器的导纳矩阵和频率响应,其中采用复阻抗模型考虑了叉指电极与自由表面的阻抗不连续的因素。本方法能够模拟指间反射、三次行程、指条寄生阻抗以及外围电路等对器件性能的影响;理论模拟与实验结果吻合。

The slanted transducer can be divided into conventional transducer along to SAW propagation axis, and the slanted transducer can be considered as the parallel connection network of many conventional transducers, based on Mason equivalent circuit model and its modification 'mixed circuit' model, the inductance matrix of conventional filter and the response of slanted transducer can be deduced. The impedance discontinuity is analyzed by complex impedance model. As a result, the internal reflection within IDTs, triple transit echo, parasite impedance of finger, and peripheral circuits can be considered in this method. A typical filter is analyzed numerically and the theoretical simulation is found to agree with the experimental.