为了减小窄带滤波器的插入损耗,在梯形拓扑的基础上引入并联电容,提出了一种并联电容型梯形拓扑。利用并联电容大幅度改变反谐振点频率的特点,以牺牲较小插入损耗的代价来缩小带宽。通过谐振器设计与进化算法寻优,成功研制出一款基于SiO₂/Cu/127°YX-LiNbO₃ 结构的低插损窄带温补型声表面波(TCSAW)滤波器。实验结果表明,滤波器的中心频率为1 514 MHz,相对带宽为0.46%,带内插入损耗仅1.45 dB,过渡带20 MHz带外抑制滚降到24 dB,远带带外抑制大于30 dB,WiFi频段抑制高达48 dB,频率温度系数TCF 为-20×10^-6/℃,器件尺寸为1.1 mm×0.9 mm。

A shunt-capacitance-type ladder-type topology was proposed by adding a shunt capacitance in a laddertypetopology to further reduce the insertion loss of a narrow-band filter. The shunt capacitance was used to modifythe anti-resonant frequency of the resonator for reducing the bandwidth of the filter with sacrificing low insertionloss. A narrow-band temperature compensated SAW (TCSAW) filter with low insertion loss based on a SiO₂/Cu/127°YX-LiNbO₃ structure was developed successfully via resonator design and evolutionary algorithm optimization.The experimental results indicate that the center frequency of the filter, relative bandwidth, and passband insertionloss are 1 514 MHz, 0.46%, and only 1.45 dB,respectively. Further, the attenuation at the frequency 20 MHzoutside the passband decreases to 24 dB, remote out-of-band attenuation is greater than 30 dB, attenuation at theWiFi band is up to 48 dB, TCF is -20×10^-6/℃, and the size of the device is 1.1 mm×0.9 mm.

TN65;TN713