声表面波器件中非同步区域体波散射的抑制

用有限元/边界元法(FEM/BEM)研究了表面波器件中非同步区域中体波散射引起的损耗。以典型的hiccup单端对谐振器作参考结构,用结构参数缓慢变化的间隙取代其中间的自由间隙。研究发现,改变间隙参数可在保持谐振频率不变的同时,提高谐振器的品质因数值。对分布间隙和风琴间隙两种间隙结构进行对比,结果表明,前者优于后者。将传统DMS滤波器中的金属化间隙以分布间隙取代,可找到一个优化的分布间隙结构,使插损提高0.3 dB。

Suppression of Bulk Wave Scattering on Non-synchronous Area in SAW Devices

The losses due to bulk wave scattering on non-synchronous area in SAW device was studied using boundary element method combined finite element method(FEM/BEM).We used a typical one-port hiccup resonator as reference structure.Using gap with gradually changing parameters to replace the central free gap in hiccup resonator,we found that it is possible to significantly increase its Q-factor while keeping the resonant frequency unchanged.Two kinds of structures were studied and compared,one is "distributed" gap,another one is the so-called "accordion" gap.It is found that distributed gap is better than accordion gap.We replaced the metallized gaps in the traditional DMS filter with distributed gaps.By numerical simulation we can find an optimal combination of pitch and metallized ratio of the gaps,reducing the insertion loss by about 0.3 dB.