US 5,256,927 A · Surface acoustic wave element having a wide bandwidth and a low insertion loss

Abstract

A surface acoustic wave element has a low insertion loss in one direction and a wide band width. This surface acoustic wave element has first and second interdigital electrodes each having a thickness on a piezoelectric or electrostrictive substrate. In a first interdigital electrode for exciting a surface acoustic wave, positive and negative electrodes are alternately arranged such that their electrode widths and periods are gradually decreased in a direction of propagation of the surface acoustic wave. In a second interdigital electrode for receiving the surface acoustic wave, positive and negative electrodes are alternately arranged such that their electrode widths and periods are gradually increased or decreased in the direction of propagation of the surface acoustic wave.

Claims19

Dependent claims

A surface acoustic wave element wherein a first surface acoustic wave transducer for exciting a surface acoustic wave and a second surface acoustic wave transducer for receiving the surface acoustic wave are provided on a piezoelectric or electrostrictive substrate in a manner where said transducers are opposed to each other in the propagation direction of the surface acoustic wave and wherein:

the first surface acoustic wave transducer comprises a first interdigital electrode constituted by positive and negative electrodes alternately arranged in a manner whereby the electrode width and the period thereof are gradually decreased in the direction of propagation of the surface acoustic wave;
the second surface acoustic wave transducer comprises a second interdigital electrode constituted by positive and negative electrodes alternately arranged in a manner whereby the electrode width and the period thereof are gradually increased in the direction of propagation of the surface acoustic wave;
Zm/Zg of each of said first and second surface acoustic wave transducers is smaller than 1 wherein Zm is the acoustic impedance of a metal film constituting the positive and negative electrodes and Zg is the acoustic impedance of an electrode gap between the positive and negative electrodes.

A surface acoustic wave element wherein a first surface acoustic wave transducer for exciting a surface acoustic wave and a second surface acoustic wave transducer for receiving the surface acoustic wave are provided on a piezoelectric or electrostrictive substrate in a manner whereby the transducers are opposed to each other in the propagation direction of the surface acoustic wave and wherein

said first surface acoustic wave transducer comprises a first interdigital electrode constituted by positive and negative electrodes alternately arranged in a manner whereby the electrode width and the period thereof are gradually increased in the direction of propagation of the surface acoustic wave;
and
said second surface acoustic wave transducer comprises a second interdigital electrode constituted by positive and negative electrodes alternately arranged in a manner whereby the electrode width and the period thereof are gradually increased in the direction of propagation of the surface acoustic wave.

Dependencies are inferred from the claim text.

Surface acoustic wave element having a wide bandwidth and a low insertion loss

Life of this patent

Surface acoustic wave element having a wide bandwidth and a low insertion loss

Life of this patent

Abstract

Claims19