Tseng Wei-Hsien, Wu Ruey-Beei
Graduate Institute of Communication Engineering, National Taiwan University, Taipei 10617, Taiwan.
Micromachines (Basel). 2024 Aug 26;15(9):1075. doi: 10.3390/mi15091075.
This study proposes a single-stage lattice-type acoustic filter using an analytical solution method for either a narrow passband filter or a wider passband filter using two kinds of parameter assignments in the Butterworth-Van Dyke (BVD) model. To achieve the goal of a large bandwidth or high return loss, two first-order all-pass conditions are used. For multi-stage lattice-type filters, the cost function is defined and design parameters are extracted by using pattern search, while the initial values are provided through single-stage design to shorten optimization time and allow convergence to a better solution. This method provides the S-parameter frequency response for the filter on the YX 42° cut angle of lithium tantalate (electromechanical coupling coefficient of about 6%) that can meet the system specifications as much as possible. Finally, the three-stage lattice-type was applied to various 5G bands with a fractional bandwidth of 2-5%, resulting in a passband return loss of 10 dB and an out-of-band rejection of 40 dB or more.
本研究提出了一种单级晶格型声滤波器，该滤波器在巴特沃思 - 范戴克（BVD）模型中使用解析解法，针对窄带通滤波器或宽带通滤波器采用两种参数赋值方式。为实现大带宽或高回波损耗的目标，使用了两个一阶全通条件。对于多级晶格型滤波器，定义了成本函数，并通过模式搜索提取设计参数，同时通过单级设计提供初始值，以缩短优化时间并实现更好的收敛。该方法提供了钽酸锂YX 42°切割角（机电耦合系数约为6%）上滤波器的S参数频率响应，该响应能尽可能满足系统规格。最后，将三级晶格型滤波器应用于分数带宽为2 - 5%的各种5G频段，得到的通带回波损耗为10 dB，带外抑制为40 dB或更高。
