一种新型的声表面波窄带滤波器

A Novel Narrow Bandpass SAW Filter

在同一基片上平行放置三个相同的ＳＰＵＤＴ滤波器，这三个滤波器的中心距彼此相差λ／３。通过并联获得了在给定带宽下比一般滤波器更短的长度，并在匹配的条件下，具有更小的转换损耗和输入输出反射。报道了采用此方法制作的中心频率１００ＭＨｚ，３ｄＢ带宽０．５ＭＨｚ的滤波器，其插损为１５ｄＢ，长度仅为５．５ｍｍ。

Three identical SPUDT filters are placed in parallel on the same substrate, the IDT's central seperations of the three filters have a difference of λ/3 between each other. By means of shunting,a shorter chip length less than a commonly single filter is obtained for a given bandwidth.Moreover,the device possesses low conversion loss and low input/output renections when matched.Adopting this new method,we fabricated an experimental filter with center frequency of 100MHz and 3 dB bandwidth of 0.5 MHz.The insertion loss was 15 dB and the chip length was only 5.5 mm.