Surface acoustic wave filter

Abstract

The invention discloses a sound surface wave filter which comprises a piezoelectricity substrate, wherein an input interdigital transducer and an output interdigital transducer are arranged on the piezoelectricity substrate along the sound surface wave transmission direction, the input interdigital transducer is composed of an upper weighted interdigital transducer, a middle weighted interdigitaltransducer and a lower weighted interdigital transducer which are parallel to each other and share four bus bars for use, an upper bus bar of the middle interdigital transducer and a lower bus bar ofthe upper interdigital transducer share a same bus bar L2 for use, a lower bus bar of the middle interdigital transducer and an upper bus bar of the lower interdigital transducer share a same bus barL3 for use, an upper bus bar L1 of the upper interdigital transducer and a lower bus bar L4 of the lower interdigital transducer are both connected to switch input feet, the bus bar L2 is connected to a signal input foot, and the bus bar L3 is earthed. The filter has the advantages of low cost and small volume, is mainly applied for multi-mode television medium frequency wave filtering, and can realize different modes or bandwidth switching by a switch.

Description

A surface acoustic wave filter technical field The invention relates to a surface acoustic wave filter, in particular to a surface acoustic wave filter capable of switching between different systems or bandwidths through a switch. Background technique With the development of analog TV in the direction of multi-standard and full-standard, and the rapid development of digital TV also needs to switch between different bandwidths. The SAW TV IF filter is the throat of the TV IF channel. Carrier and other related signals must be processed through it, so it is necessary to require the surface acoustic wave to be able to adapt to signal processing of different formats. The working principle of the surface acoustic wave filter is to use the planar technology of semiconductor integrated circuits to vapor-deposit a certain thickness of aluminum film on the surface of the piezoelectric substrate (lithium niobate, lithium tantalate), and then place two designed similar fingers The m...

AI Technical Summary

Problems solved by technology

At present, analog TV mainly has three standards: NTSC, PAL, and SECAM, which have different bandwidth requirements. Digital TV also has different bandwidths of 6MHz, 7MHz, and 8MHz. Earlier TVs used two surface acoustic wave filters with different functions to achieve different Therefore, the size of the device is large and the cost is high; later, the above-mentioned switching function is realized by putting the surface acoustic wave filter chips with different functions in the same package, but the above-mentioned technology requires a larger chip , the input impedance of different standards or different bandwidth requirements is quite different, and it is difficult for circuit designers to match

Images