BAW滤波器声-电磁协同仿真中的共地电感效应

Common ground inductance effect in combined acoustic-electromagnetic simulation of bulk acoustic wave filter

针对体声波(BAW)滤波器声-电磁协同仿真结果中滤波器的左传输零点向左偏移的现象,验证仿真中共地电感效应的存在并分析其对滤波器性能的影响。通过分别改变BAW滤波器原始布局中的并联薄膜体声波谐振器(FBAR)P1和P4引线到地的位置,即将并联FBAR P1和P4引线到地的路径分别变短后进行声-电磁协同仿真。结果对比表明:声-电磁协同仿真中并联FBAR引线到地与输入、输出端口之间存在共地电感效应。将并联FBAR引线到地的路径变短,滤波器在声-电磁协同仿真中形成的共地电感效应减小,带外抑制性能变好。共地电感效应对于并联FBAR谐振区面积越小的支路影响越大。故在BAW滤波器声-电磁协同仿真中需考虑共地电感效应对滤波器左传输零点和左带外抑制性能的影响。

Aiming at the phenomenon that left transmission zero of bulk acoustic wave（BAW）filter has a leftward deviation in combined acoustic-electromagnetic simulation,we verified the existence of common inductance effect in simulation and analyzed the influence of common ground inductance on filter performance.We changed positions of parallel thin-film bulk acoustic resonators（FBARs）P1 and P4 to ground in the original layout of the BAW filter（shortening paths to the ground）,respectively.Then combined acoustic-electromagnetic simulation of filter was done.The results show that：common ground inductance effect existed between parallel FBAR to ground and input port and output port in combined acoustic-electromagnetic simulation.When the paths of parallel FBARs to ground were shortened,the common ground inductance effect was reduced in combined acoustic-electromagnetic simulation,and out of band rejection was better.The influence of common ground inductance effect on the smaller area parallel FBAR was more obvious.So the influence of common inductance effect on left transmission zero and left out of band rejection should be considered in combined acoustic-electromagnetic simulation of BAW filter.