Switch type two-channel SAW filter

Abstract

The invention provides a switching type double channel surface acoustic wave filter, comprising two input end interdigital energy converters integrated on a piezoelectric crystal wafer, a common output end interdigital energy converter and a shielding strip between the input end interdigital energy converter and the common output end interdigital energy converter, wherein envelope lines of the two input end interdigital energy converters respectively extend from the center of a surface acoustic wave transmission channel to two ends slantingly along the interdigital conflux strip on one side, the interdigital overlapping area of the interdigital energy converter of the first input end on the center of the surface acoustic wave transmission channel is larger than the interdigital overlapped area extending to the two ends slantingly; and the interdigital overlapping area of the interdigital energy converter of the second input end on the surface acoustic wave transmission channel may be not the largest, and the interdigital overlapping area extending to the two ends slantingly is overlapped in the surface acoustic wave transmission channel of the interdigital overlapped energy converter of the first input end. By the switching type, the switching type double channel surface acoustic wave filter realizes different filter functions. The switching type double channel surface acoustic wave filter effectively reduces the occupied area of chip and easily realizes the compensation in the weighing design.

Description

technical field [0001] The invention relates to a band-pass filter, in particular to a surface acoustic wave filter integrated on a piezoelectric crystal chip. Background technique [0002] When a voltage is applied to the electrode of a substrate material with piezoelectric properties (such as lithium niobate single crystal material), mechanical distortion will be formed in the crystal lattice of the piezoelectric crystal sheet. When the voltage signal is loaded on the piezoelectric crystal sheet, a surface acoustic wave will be formed in the lattice on the surface of the piezoelectric crystal sheet. while rapidly decreasing elastomechanical waves. [0003] SAW filters have the characteristics of bandpass filters. The realization of the band-pass filtering function of the surface acoustic wave filter is based on the surface acoustic wave formed in the above-mentioned lattice. The basic structure of the surface acoustic wave filter is to make an aluminum film with a certa...

AI Technical Summary

Problems solved by technology

[0005] The shortcoming of above-mentioned design method is: the input end interdigital transducer A of separate design and A1 all are that the interdigitated overlapping length of middle part interdigitation is bigger (as figure 1 DA and DA1 in ), while the overlapping length of crossover at both ends is small

Since the second channel B is obtained by adding or subtracting two separately designed input IDTs through the pulse specification, in order to reduce the chip area, the width TDB of the second channel must be made as large as possible The ground is small, so the compensation space for the weighted design is narrow, which becomes extremely difficult, and even fails to meet the design requirements, deteriorating the filter performance

In order to meet the design requirements, the width of the second channel B can only be increased, which in turn increases the chip area and increases the cost

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