JPS58114518A - Surface wave element - Google Patents

Abstract

PURPOSE:To attain a surface wave element usable at high frequencies and band, by cutting off a Y-cut plate of a berlinite crystal with a prescribed range of rotary angle. CONSTITUTION:A rotary Y-cut plate 2 is made by cutting off a berlinite substrate in the length l toward the broadwise direction X, Y at an angle theta counter clockwise by taking the X axis of the Y-cut plate 1 as a center. This cut azimuth is represented as (YXl)theta in accordance with the IRE standard. An input and output transducer 3 is formed toward the Z axis after the rotation of the plate 2, and an SH wave surface wave is excited with the electrode film of the transducer 3. Assuming that the rotary agnle theta is in the range of +37.5 deg.- +43.5 deg., an element having excellent temperature characteristics can be attained at high frequencies and band.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an SH wave type surface element using verlinite (α-Azpot) crystal.

(2) Background of the technology Since surface wave devices can be easily realized that can be used up to several hundred MHz, they are widely used as filters and delay lines for various communication devices.

(3) Prior art and problems As a conventional surface wave device material, LiNb0. , LiTa0. Crystals etc. are used. However, these crystals have poor temperature stability;
This is extremely difficult to achieve when high stability is strictly required.6 On the other hand, quartz crystals such as ST cut have very good temperature stability, but on the other hand, they have a small electromechanical coupling coefficient and low band.

This is extremely difficult to achieve with low-loss surface wave filters. Recently, verlinite crystal has been proposed as a crystal material that compensates for these drawbacks. A cutting direction with good temperature characteristics has already been found for Rayleigh wave type surface waves using this crystal, but since the phase velocity 1y is relatively small, if the goal is to increase the frequency of the device, for example at IGHz, It is difficult to realize a pattern using a normal optical exposure method in which the electrode finger width is about 0.8 μm.

(4) Purpose of the invention The present invention solves the above-mentioned problems and
The object of the present invention is to provide a surface wave device that has better temperature characteristics than crystals such as O5, has a larger coupling coefficient than quartz crystals, and is capable of higher frequencies.

(5) Structure of the invention The above-mentioned object is to
In the SH wave surface wave element that constitutes a cross-finger disk transformer in the two-axis directions of a barlinite rotating Y-cut plate represented by θ, the rotation angle θ of the rotating Y-cut plate is +37.5.
This is achieved by providing a surface wave element characterized in that the temperature range is between (degrees) and +43.45 (degrees).

(6) Examples of the invention Examples of the invention will now be described in detail with reference to the drawings. Fig. 1 is a schematic diagram showing the Y-cut i and the rotating Y-cut plate, Fig. 2 is a diagram showing the phase velocity νS of the rotating Y-cut plate with respect to the rotation angle θ, and Fig. 3 is a diagram showing the temperature coefficient Tf with respect to the rotation angle θ. The figure shown in Fig. 4 shows the mechanical coupling coefficient 26 for peeping mechanical coupling with respect to the rotation angle θ.
It is a figure showing thatch. .

In the figure, 1 is a Y-cut plate, 2 is a rotary Y-cut plate, and 3 is an input/output transformer.

The rotating Y-cut plate 2 is connected to the Y-cut plate 1 indicated by a broken line in FIG.
The barlinite base plate is rotated by θ [degrees] counterclockwise around Xf'111 with respect to the plate thickness Y.

It is cut at length t in the X direction. This cutting direction is expressed as (YXt)θ in the IRE standard.

Such rotation Y axis) @2 rotation Z axis, that is, Z
In the axial direction, an input/output transformer 3 with a crossed fingerboard is formed as shown in FIG. Ru.

Regarding the groove of the present invention, as a result of studies on surface acoustic wave elements using such verlinite crystals, the following was found.

That is, as shown in Fig. 2, the dependence of the phase velocity 27s of the moat wave on the rotation angle θ is confirmed to be the maximum when the rotation angle θ is 20 to 40 degrees, and the phase velocity 'lfs is 4200 to 4300 s/s. It was done.

Further, as shown in Fig. 3, the rotation angle θ is 37.5 to 43
．． It was confirmed that at 5 degrees, the temperature coefficient Tf was very small, less than 1X10-,/°C. When the rotation angle θ is in the range of 37.5 to 43.5 degrees, the phase velocity 'lrS is determined from Fig. 2 as 4200 m/B to 42603.
- It was found that there is a cutting direction in which the phase velocity is very large at m/s and the temperature characteristics are also good.

Even higher? In the vicinity of rotation angle θ of e, h/λ=3X
10'' (h: gold electrode film thickness, λ: electrode period) The electrical (geometrical coupling coefficient 2△'/Z-) was measured and the rotation angle θ was 37.5 to 43. It was confirmed that the electromechanical coupling coefficient was 0.012 to 0.014 in the range of 5 degrees, which is approximately 10 times the mechanical coupling coefficient of a Rayleigh wave type surface wave element using an ST-cut crystal. It has been found that by cutting a Y-cut plate of verlinite crystal at 30° C., a surface acoustic wave element that can be used at high frequencies and over a wide band, has low loss, and has good temperature characteristics can be provided.

(7) Details of the invention According to the present invention, as explained, the phase velocity.

Since it is possible to increase the mechanical coupling coefficient, the loss is small and it is easy to increase the frequency. This will result in lower insertion loss and wider bandwidth.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a Y-cut plate and a rotating Y-cut plate,
Figure 2 shows the phase velocity S versus the rotation angle θ of the rotating Y-cut plate.
FIG. 3 is a diagram showing the temperature coefficient Tf with respect to the rotation angle θ, and FIG. 4 is a diagram showing the electromechanical coupling coefficient 2Δ with respect to the rotation angle θ.
It is a figure showing %. 1... Y-cut plate, 2... Rotating Y-cut plate, 3... Cross-finger plate transducer, θ・
... Rotation angle, S ... Phase velocity, Tf ...
...Temperature j corpse coefficient, 2△7,... ...Electromechanical coupling coefficient. Rotation angle θ Fig. 4 rotation @ angle θ

Claims (1)

[Claims] According to the IRE standard, in an SR corrugated surface wave element configured with an interdigitated input/output transformer in the Z-axis direction of a barlinite rotating Y-cut plate whose cutting direction is represented by (Y)l)θ, the rotation A surface wave element characterized in that the rotation angle θ of the Y-cut plate is in the range of +37.5 (degrees) to +435 (degrees).