JP2520136Y2 - Surface acoustic wave device - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a surface acoustic wave device, and in particular, a binary tree pattern as a means for uniformizing distribution in a gate for a surface acoustic wave (hereinafter abbreviated as SAW) convolver. Related to the improvement of the connection arrangement structure.

[Summary of Invention] A SAW convolver and a binary tree pattern (Binary Tree Patern) arranged side by side in the package are housed in a package, and each output terminal of the output electrode of the convolver is the binary tree pattern. The surface acoustic wave device is connected to each of the input terminals and one binary tree output terminal is derived from the above pattern.

[Prior Art] FIGS. 4 to 6 show a conventional SAW convolver. In the figure, 1 is a piezoelectric substrate such as lithium niobate, 2, 3
Is an input electrode made of a metal film of aluminum or the like, 4 is a rectangular output electrode made of a metal of aluminum or the like provided between the input electrodes 2 and 3, and 8 and 9 are absorptions for attenuating unnecessary surface acoustic wave. It is a material.

When electric signals are applied to the terminals 5 and 6 of the input electrodes 2 and 3 in FIG. 4, they become surface acoustic waves from the electrodes 2 and 3,
It propagates on the piezoelectric substrate 1.

For example, the SAW generated from the input electrode 2 propagates left and right, but the SAW propagating leftward is absorbed by the absorber 8,
SAW reflected from this end and propagating to the right again can be eliminated. Of the SAWs generated from the input electrode 3 and propagated to the left and right, the SAWs similarly propagated to the right are absorbed by the absorber 9.

That is, the surface acoustic wave convolver has a SAW S ₂ from the input electrode 2 and a SAW S ₁ from the input electrode 3 as shown in FIG.
And are coupled via the nonlinear interaction of the piezoelectric substrate 1, and as a result, the convolution output electric signal can be taken out from the output terminal 7.

The output electrode 4 has a length 1 with respect to the SAW propagation direction x as shown in FIG. 6, and this length 1 determines the processing time of the convolver, so it is very long, for example, l = 40-
It may be 50 mm.

The convolution signal is output to the output electrode 4 along the x direction.
Is the integration (sum) of the signals generated in each part of. However, the output electrode 4 forms a finite length distributed constant line having a length l. Therefore, when the output is taken out from one point in the center as shown in FIG. 6, a phase difference occurs in the convolution signal generated in each part of the output electrode 4 along the x direction. This is called the distribution in the gate on the output electrode 4, and it is desirable to make it as uniform as possible. As a means for making the distribution within the gate uniform, one shown in FIG. 7 has been proposed. In FIG. 7, the convolver chip 1 of FIG. 6 is arranged in parallel with the convolver chip 1 in which a binary tree pattern 11 having a structure in which strip lines of a mold which are housed in a package 18 and formed on an alumina substrate 10 are stacked and connected. . The binary tree pattern 11 and each output terminal 4'of the convolver output electrode 4 are
Bonding wires 19 are connected through the input terminals 12 of the tree pattern 11. Further, the entire convolution output is connected from the output terminal 15 of the binary tree to the output terminal 17 outside the substrate by the bonding wire 16.

[Problems to be Solved by the Invention] The convolution signals thus generated in the respective parts of the output electrode 4 pass through a large number of output taps, and the signals from those taps pass through a binary tree to have the same phase. Since it reaches the output terminal 17, the distribution in the gate can be made very uniform. However, as is clear from FIG. 7, the binary tree pattern 11 is the convolver chip 1
Will be much larger than Therefore, the package 18 is also large, and the package cost is high. Further, an alumina substrate provided with a binary tree pattern 11
It is necessary to place 10 on the package 18 in parallel and close to the convolver chip 1, but the input electrodes 2 and 3 of the convolver chip have a pattern with a line width of several μm. turn into. It therefore has the drawback of being very cumbersome to handle. Further, the binary tree is designed to have a desired characteristic impedance, but the thickness of the alumina substrate 10 is a large design parameter, and when the alumina substrate 10 is thick, it becomes considerably thicker than the convolver chip 1 in FIG. However, there is also a drawback that the wire bonding work for connecting them becomes very difficult.

Therefore, the thickness of the alumina substrate 10 is limited, and there is a drawback that the degree of freedom in design is narrowed.

[Object of the Invention] Accordingly, an object of the present invention is to provide a surface acoustic wave convolver having a binary tree pattern that is inexpensive, easy to handle in the assembly process, and that can obtain good characteristics.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention comprises a folded binary tree pattern arranged in the package in the lateral direction of the SAW convolver as follows. Is the gist.

That is, the binary tree pattern has an input terminal connected to each output terminal of the convolver and a plurality of substantially-shaped strip lines, and strip lines of each stage except the uppermost stage of the pattern are It is an even number, and it is provided so that the die shape direction of each strip line is opposite and the strip shape of each stage is opposite, and both ends of the strip line of each stage are the two strips of the previous stage.
One binary tree output terminal is derived from the middle point of the uppermost strip line, connected to each middle point of the line, and the binary tree output is output from each end of each lowermost strip line. The distance to the terminal is configured to be the same for all paths.

[Operation] Since the output signal of the SAW convolver is taken out from each of the output terminals of the output electrode through the one output terminal via the binary tree pattern, it is necessary to make the distribution within the gate at the output electrode of the convolver uniform. You can
Moreover, in this case, since the binary tree patterns are arranged side by side in the lateral direction of the convolver, the assembling process is also simplified, and the direction of the strip line of the mold shape of each step constituting the above pattern is reversed. Since the both ends of the binary tree pattern are connected to the two middle points of the preceding stage, the minimum required width for the binary tree pattern can be shortened and formed smaller than the conventional one. Therefore, the entire package is downsized, and the degree of freedom in designing the characteristic impedance of the binary tree pattern is increased.

[Embodiment] The present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 shows the structure of a SAW convolver and a binary tree pattern according to the present invention in a package. In the figure, 20 is a SAW convolver, and 30 is a binary tree tree arranged in parallel in the lateral direction of the convolver.
It is stored in the package 40 in a pattern. The SAW convolver 20 has the same output electrode 24 and input electrode as the conventional one.
Has 22,23 and also binary tree pattern 3
0 is composed of a plurality of strip-shaped strip lines 32 formed on the alumina substrate 31, and the input terminals 34, which are the end portions of the strip line 32a at the lowest stage, are the terminals 24 of the output electrode 21 of the convolver. To the bonding wire 25.

Further, the binary tree pattern 30 has an even number of strip lines 32b except for the uppermost stage, and the strip lines 32b in each stage are halved. It is provided and its both ends are connected to the midpoints of the two preceding strip lines. One binary tree output terminal 33 is provided from the middle point of the strip line 32c at the highest stage, and the distance from each end of each strip line 32a at the lowest stage to the binary tree output terminal 33 is set. It is the same for all paths.

With the above configuration, the distribution in the gate of the output electrode 21 of the SAW convolver 20 can be made uniform, and the minimum width h required for the binary tree pattern is considerably shortened compared to the conventional h '. To be done.

This is clear with reference to FIG. 2, for example.

Further, as is clear from FIG. 3 (a), in the case of the conventional binary tree pattern configuration, the position of the output terminal O ₁ is separated from the position of the input terminal group I ₁ by h. Becomes large in proportion to the number of input terminals.

On the other hand, according to the binary tree pattern of the present invention, h ′ increases in proportion to the number of input terminals I ₂ ,
It can be shorter than h, and since the output side strip line does not greatly separate from the input terminal even if the number of input terminals increases, it is possible to place the output terminal in the center of the input terminal and reduce the size of the pattern. It is valid.

[Advantages of the Invention] As described above, according to the present invention, the package that houses the convolver chip is downsized. The size of the convolver package can be reduced by making it smaller.
Further, by disposing the binary tree separately from the convolver chip, consideration for the convolver chip itself becomes unnecessary.

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of the SAW convolver according to the present invention, FIG. 2 is a comparison diagram of the present invention and a conventional binary tree pattern, and FIG. 3 is a present invention and the conventional binary tree pattern. 4, FIG. 5, FIG. 6 and FIG. 6 are schematic diagrams showing an example of a conventional surface acoustic wave convolver, and FIG. 7 shows a conventional surface acoustic wave convolver having a binary tree pattern. It is a schematic diagram showing. 20 …… SAW convolver, 30 …… binary tree pattern, 40 …… package, 21 …… output electrode, 32 …… strip line, 33 …… binary tree output terminal.

Claims (2)

(57) [Scope of utility model registration request] 1. A packaged surface acoustic wave convolver, a plurality of output terminals drawn out from an output electrode of the convolver in the package, and a bent type arranged side by side in the package in the lateral direction of the convolver. A binary tree pattern, the binary tree pattern having an input terminal connected to each output terminal of the convolver and a plurality of substantially-shaped strip lines, excluding the topmost stage of the pattern. The number of strip lines in each stage is an even number, and the above strip lines are halved for each stage and the mold shapes of the strip lines are arranged in opposite directions. Part is connected to each middle point of the two strip lines in the previous stage, and one binary is formed from the middle point of the strip line in the top stage. Tory output terminal is derived,
A surface acoustic wave device characterized in that the distance from each end of the strip line of the lowest stage to the binary tree output terminal is made equal for all paths. 2. The utility model registration claim 1, wherein the output terminal of the binary tree pattern is arranged so as to be bent from the final strip line toward the input terminal. Surface acoustic wave device.