Low loss ladder type SAW filter in the range of 300 to 400 MHz
Low loss ladder type SAW filter in the range of 300 to 400 MHz
复制标题
300 至 400 MHz 范围内的低损耗梯型 SAW 滤波器
DOI：
10.1109/ultsym.1994.401568
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Y. Satoh
中科院分区：
文献类型：
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作者：
M. Ueda;O. Kawachi;K. Hashimoto;O. Ikata;Y. Satoh
采用36°旋转Y切LiTaO_3梯形电路结构，研制了300 ~ 400 MHz通信系统用低损耗声表面波滤波器。这种滤波器具有低损耗和高阻带抑制，但会出现寄生模式，这取决于谐振器的电极厚度和反射器的电极间距。低频范围滤波器需要大于7%波长的厚Al电极来将寄生模式的谐振频率移动到高于通带频率范围的频率范围。为了减小寄生响应，通过模拟和实验研究了比Al更具有质量效应的电极图案和电极材料的设计。通过优化反射器的电极间距可以抑制寄生响应。通过使用Au膜，可以将约1.5%波长的薄膜应用于滤波器。研制了频率范围为300 ~ 400 MHz、带宽为2 ~ 4%的SAW滤波器，采用SMD型5×7× 1.4mm陶瓷封装，最小插入损耗为2dB，衰减特性约为40 dB。滤波器输入输出阻抗均为50 Ω
Low loss SAW filters in the range of 300 to 400 MHz for communication systems have been developed, which have ladder circuit structure using 36° rotated Y-cut LiTaO3. This type of filter has low loss and high stop band rejection, however, a spurious mode appears, which depends on electrode thickness and a reflector's electrode pitch of a resonator. Low frequency range filters need thick Al electrodes more than 7% of wave length to shift the resonant frequency of spurious mode to a frequency range higher than the pass-band frequency range. To reduce the spurious response, the design of an electrode pattern and electrode material having more mass effect than Al were investigated by simulation and experiment. The spurious response can be suppressed by optimizing a reflector's electrode pitch. By using Au film, thin film of about 1.5% of wave length can be applied to a filter. SAW filters in the range of 300 to 400 MHz with fractional band width from 2 to 4% were manufactured and mounted in SMD type 5×7×1.4 mm ceramic packages, which have 2 dB minimum insertion loss and attenuation characteristics of about 40 dB. Input and output impedance of filter are 50 Ω