Surface elastic wave filter, duplexer and module

Abstract

A surface elastic wave filter comprises a harmonic oscillator, the harmonic oscillator comprises a substrate, a piezoelectric layer and an IDT electrode, the piezoelectric layer is formed on the substrate and made of piezoelectric materials, the IDT electrode is formed on the piezoelectric layer, the substrate is composed of a high-impedance semiconductor or an insulator, and the dielectric layer is formed on the substrate. The wavelength [lambda] of the elastic wave is determined according to the electrode period of the IDT electrode, the elastic wave can be divided into a plurality of regions having different thicknesses, the IDT electrodes are respectively positioned on the plurality of regions to constitute the resonators, and the resonators formed in the plurality of regions are connected to each other to constitute a resonator. According to the surface elastic wave filter, the duplexer comprising the surface elastic wave filter and the module comprising the surface elastic wave filter, high-frequency noise can be restrained, and meanwhile a high Q value is kept.

Description

technical field [0001] The present invention relates to a surface elastic wave filter, a duplexer and a module including the surface elastic wave filter. Background technique [0002] In communication device terminals such as mobile phone terminals and portable information terminals, elastic wave devices used in antenna filters or duplexers require higher Q values. Among elastic wave devices, bulk elastic wave filters and surface elastic wave filters are included. Among the aforementioned elastic wave devices, although the use of surface acoustic wave filters is the mainstream, surface acoustic wave filters have a problem of lower Q values ​​than bulk elastic wave filters. [0003] In order to improve the Q value, as described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-534886), by using a substrate made of silicon or sapphire, a substrate made of lithium tantalate or lithium niobate is bonded as thin as possible. The multilayer film structure of t...

AI Technical Summary

Problems solved by technology

This high frequency noise can adversely affect the damping characteristics of the device

As a result, passband systems used in mobile communication equipment are adversely affected, or signals transmitted from said passband systems are likely to adversely affect systems in other frequency bands

However, it is difficult to suppress such noise only by adjusting the layer thickness of the piezoelectric layer constituting the elastic wave filter.

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