JPS61199314A - Surface acoustic wave resonator - Google Patents

Abstract

PURPOSE:To attain miniaturization of the size of an element by forming circularly a comb-line electrode and a grating reflector while taking a point as a center so as to improve the resonance efficiency. CONSTITUTION:The comb-line electrode 2 and the grating reflectors 3, 4 are formed as a circle while taking a point as a center. For example, the com-bline electrode 2 and the grating reflectors 3, 4 are formed as a circle around a point on a piezoelectric substrate 1 by an Al thin film having a nearly 1mum of film thickness. As the forming method, the photo resist etching method is used. Thus, a high energy confinement is attained at the center of the com-bline electrode so as to improve the resonance efficiency. Further, the size of the element is made small by the improvement of the resonance efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a surface acoustic wave resonator equipped with a grating reflector, and particularly to a surface acoustic wave resonator suitable for improving characteristics and reducing the size of the surface acoustic wave resonator.

[Background of the invention]

The basic electrode configuration of a surface acoustic wave resonator is conventionally known as a configuration in which a piezoelectric substrate has a comb-toothed electrode on the surface and grating reflectors are arranged on both sides of the comb-toothed electrode. In such a configuration, the surface waves excited by the tooth-shaped electrodes spread as they propagate, reducing efficiency, so an electrode configuration as shown in FIG. 6 was used.

In other words, as described in JP-A-57-11521, a reflector is formed in a parabolic shape to efficiently reflect surface waves. However, in the above-mentioned conventional technology, in order to increase the reflectance, No consideration was given to the disadvantage that increasing the number of grating reflectors would increase the size of the element in the lateral direction, making it difficult to handle, or to improve resonance efficiency.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface acoustic wave resonator with improved co-imaging efficiency and a technique for reducing the size of the element.

[Summary of the invention]

In the present invention, we focused on comb-shaped electrodes and grating reflectors.

That is, the comb-shaped electrodes and the grating reflector were formed into circular shapes centered on the same point. In conventional resonators, the surface waves excited from the comb-like electrodes spread in the traveling direction, so the grating reflector was formed in a parabolic shape, but in the present invention, the energy is concentrated near the center of the excitation electrode. In order to improve the focusing, the common IT pole and the grating reflector are arranged in a circular shape centered on the same point.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. A comb-shaped electrode 2 and a grating reflector 3 are disposed on a piezoelectric substrate 1.
．． and 4 were formed of At thin films with a film thickness of 1 μm. A photoretching method was used as the manufacturing method. However, the center frequency is 696MHz, and there are no grating ratings.

It was designed with 25 pairs of comb-shaped electrodes. The comb-shaped reflector and the grating reflector were formed in a circular shape centered at the same point as shown in FIG. According to this embodiment, it is possible to trap a high amount of energy in the central portion of the comb-like electrode, which has the effect of improving resonance efficiency. Furthermore, the improvement in the efficiency of co-photography has the effect of making the element smaller.

FIG. 3 shows another embodiment of the invention. In this embodiment, the common electrodes of the grating reflectors are arranged in a dispersed manner.

〔Effect of the invention〕

According to the present invention, since the comb-shaped electrodes and the grating reflector are refined around the same point (the surface waves excited by the comb-shaped electrodes can be reflected without escaping, the resonance efficiency can be improved). Also, the improvement in resonance efficiency has the effect of making the element smaller.For example, compared to the conventional example, with the same number of gratings, the reflection coefficient is improved by about 25 mm.The improvement in the reflection coefficient also reduces the element size. It can be reduced by about 23 points.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing one embodiment of the surface acoustic wave resonator of the present invention, FIG. 2 is a plan view showing another embodiment of the surface acoustic wave resonator of the present invention, and FIG. 3 is a plan view showing a conventional surface acoustic wave resonator. FIG. 2 is a plan view showing the configuration of a surface wave resonator. DESCRIPTION OF SYMBOLS 1...Piezoelectric substrate, 2...(teeth-shaped pole, 3 and FIG. 1 Z y 3rd opening)

Claims (1)

[Claims] 1. Equipped with a comb-shaped electrode provided on a piezoelectric substrate for exciting and receiving surface acoustic waves, and a grating reflector formed of a metal strip for reflecting the excited surface acoustic waves. 1. A surface acoustic wave resonator, wherein the comb-shaped electrodes and the grating reflector are formed in a circular shape centered on the same point.