US 5,729,186 A · Resonator ladder surface acoustic wave filter suppressing spurious signals

Abstract

A resonator ladder surface acoustic wave (SAW) filter, which has a wide and flat pass band without spurious signals therein is provided. An input electrode, a serial arm SAW resonator, an output electrode, a parallel arm SAW resonator and a ground electrode are respectively formed on a 41.degree.-rotated Y-cut X-propagation lithium niobate substrate. The serial arm SAW resonator comprises a pair of interdigital transducers (IDTs) to excite SAW, one of which is connected to the input electrode. The output electrode is connected to the other IDT of the serial arm SAW resonator. The parallel arm SAW resonator comprises a pair of IDTs to excite SAW, one of which is connected to the output electrode. And the ground electrode is connected to the other IDT of the parallel arm SAW resonator. The IDTs are metal films of Al or Al-based alloy, and the thickness of the metal films ranges from 2.5% to 7.5% of the electrode cycle of the IDT of the parallel arm SAW resonator.

Claims20

Dependent claims

A resonator ladder surface acoustic wave filter, comprising:

a 41.degree.-rotated Y-cut X-propagation lithium niobate substrate;
a serial arm surface acoustic wave resonator on the substrate, having interdigital transducers for exciting a surface acoustic wave;
a parallel arm surface acoustic wave resonator on the substrate, having interdigital transducers for exciting a surface acoustic wave, the interdigital transducers having an electrode cycle;
the interdigital transducers of both the serial arm surface acoustic wave resonator and the parallel arm surface acoustic wave resonator being formed from films of a metal selected from the group consisting of aluminum and aluminum alloy, the films having a thickness ranging from 2.5% to 7.5% of the electrode cycle of the interdigital transducers of the parallel arm surface acoustic wave resonator.

1 more element

A resonator ladder surface acoustic wave filter, comprising:

a 41.degree.-rotated Y-cut X-propagation lithium niobate substrate;
a serial arm surface acoustic wave resonator on the substrate, having interdigital transducers for exciting a surface acoustic wave;
a parallel arm surface acoustic wave resonator on the substrate, having interdigital transducers for exciting a surface acoustic wave, the interdigital transducers having an electrode cycle;
the interdigital transducers of both the serial arm surface acoustic wave resonator and the parallel arm surface acoustic wave resonator being formed from films of a metal other than aluminum, the films having a thickness ranging from 2.5.multidot..rho..sub.Al /.rho..sub.Me % to 7.5.multidot..rho..sub.Al /.rho..sub.Me % of the electrode cycle of the interdigital transducers of the parallel arm surface acoustic wave resonator, where .rho..sub.Al is the density of Al and .rho..sub.Me is the density of the metal other than aluminum of an electrode film material.

1 more element

Dependencies are inferred from the claim text.

Resonator ladder surface acoustic wave filter suppressing spurious signals

Life of this patent

Resonator ladder surface acoustic wave filter suppressing spurious signals

Life of this patent

Abstract

Claims20