TriQuint Semiconductor, Research and Development Department, Apopka, FL, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2010;57(2):412-20. doi: 10.1109/TUFFC.2010.1421.
When designing narrow band resonant SPUDT devices, the excitation of undesired transverse modes may result both in extra ripple in the passband and in spurious response in the stop band. To avoid these issues, it was proposed to use an approach similar to the one used for bulk-acoustic-wave devices. The principle is to add a low-velocity region at the edge of the transducer. If this edge region is properly designed, the transducer supports a so-called piston mode, i.e., a mode having a flat transverse amplitude profile across the aperture. A P-matrix model is extended to account for transverse modes in SPUDTs. The model is used to analyze both regular and piston-mode devices. Different physical possibilities to implement the low-velocity region are investigated and compared. In particular, it was found important to design the transducer so that the acoustical sources and reflectors extend into the edge region to minimize the coupling to higher order modes. From these considerations, a new implementation for piston-mode devices is proposed and demonstrated on a GSM base station 199-MHz filter. Electrical measurements as well as acoustical wave fields measured with an optical interferometer are analyzed and compared with simulations.
在设计窄带谐振 SPUDT 器件时，激励不需要的横向模式可能会导致通带内出现额外的纹波，并在阻带内产生杂散响应。为了避免这些问题，有人提出采用类似于体声波器件的方法。其原理是在换能器的边缘增加一个低速区。如果这个边缘区域设计得当，换能器就会支持所谓的活塞模式，即一种在孔径上具有平坦横向幅度分布的模式。扩展了 P 矩阵模型以考虑 SPUDT 中的横向模式。该模型用于分析常规和活塞模式器件。研究并比较了不同实现低速区的物理可能性。特别重要的是要设计换能器，使得声学源和反射器延伸到边缘区域，以最小化对更高阶模式的耦合。基于这些考虑，提出了一种用于活塞模式器件的新实现，并在 GSM 基站 199MHz 滤波器上进行了演示。对电测量以及使用光学干涉仪测量的声波场进行了分析，并与模拟结果进行了比较。
