一种实现高带外抑制声表面波滤波器结构

A SAW Filter Structure with High out-of-band Rejection

为了获得高的带外抑制，我们设计了一种单相单向换能器与镜像阻抗连结换能器结合的滤波器结构。该结构由双通道组成，每通道上由一个电级宽度控制单相单向端变迹加权换能器和一个抽指加权换能器组成，它具有带外抑制高、插损小、体积小和制作容易等优点，克服了常规滤波器级联带来的插损大，难匹配的问题。最后给出了我们制作在１２７．８６°Ｙ－ＸＬｉＮｂＯ＿３基片上的高带外抑制声表面波滤波器结果，其中心频率为７０ＭＨｚ，带宽为１．５ＭＨｚ，带外抑制大于７０ｄＢ，插损小于１３ｄＢ，芯片尺寸小于５ｍｍ×１０ｍｍ。

In order to obtain high out-of-band rejection,a filter struccture has been designed,which combines single phase unidirectional transducer(SPUDT)with mirror impedance connection transducer.The structure consists of double paths and each path is composed of a EWC apodized weighting transducer and a withdrawal weighting transducer.The structure bas the advantanges of high out-of-banb rejection, small loss, small size and easy manufacture, and overcomes the prob-lems of large loss and match difficult caused by cascade connection for conventional SAW filters.At last,the results of the SAW filter with high out-of-band rejection are given with the oenter fre-quency of 70MHz,bandwidth of 1.5MHz,out-of-band>70dB,insertion loss<13dB,the size of chip<5mm×10mm