基于SAW滤波器的电磁寄生提取

Electromagnetic Parasitic Extraction Based on SAW Filter

针对封装管壳和版图电磁寄生参数导致射频声表面波(SAW)滤波器通带变窄及驻波增大等问题,提出一种能快速提取封装管壳和版图中电磁寄生效应的方法,精准模拟了封装和版图对滤波器性能的影响。首先利用有限元法(FEM)电磁仿真软件提取封装管壳的电磁寄生参数,再使用电路仿真软件将所设计出的滤波器结合所提取的封装寄生参数和滤波器版图直接进行联合仿真,此方法不需将版图在FEM软件中再次进行电磁仿真,可提高时间利用率。此方法在中心频率为1 268 MHz、通带插入损耗小于1 dB、带内驻波小于1.6、带内波动为0.5 dB、带宽为24 MHz(相对带宽为1.8%)的SAW滤波器上进行了验证,结果表明仿真结果与实测值吻合度较高。该设计中所用的SAW谐振器均经过去嵌操作,能更精准地模拟实测滤波器的结果。

Considering the electromagnetic parasitic parameters of the encapsulated tube shell and layout,the passband of an RF surface acoustic wave(SAW) filter narrows,and the standing wave increases.This paper proposes a method to quickly extract the electromagnetic parasitic effects in the package shell and layout and accurately simulate their influence on filter performance.First,FEM electromagnetic simulation software was used to extract the electromagnetic parasitic parameters of the encapsulated tube shell.Then,circuit simulation software was employed to co-simulate the designed filter with the extracted packaging parasitic parameters and filter layout.This approach eliminates the need for repeated electromagnetic simulations in FEM software,improving time efficiency.The method was verified on a SAW filter with a center frequency of 1 268 MHz,a passband insertion loss of less than 1 dB,an in-band standing wave of less than 1.6,an in-band fluctuation of 0.5 dB,and a bandwidth of 24 MHz(relative bandwidth of 1.8%).The SAW resonators used in this design were de-embedded,allowing for more accurate simulation of the measured filter results.