JPH03253110A - Surface acoustic wave filter - Google Patents

Abstract

PURPOSE:To obtain a filter capable of suppressing the generation of ripples in a band to a low level and having high performance by arranging respective intersecting parts of weighted interdigital electrodes in the vicinity of a hot terminal. CONSTITUTION:The intersecting parts S1 to S6 indicating the weighting value of the weighted interdigital electrodes 11, 14 arranged on a piezo-electric base are arranged close to a bus bar 12 connected to a hot side terminal 1 and the electrode 14 connected to a grounded bus bar 13 is arranged so as to be extended up to the intersecting parts S1 to S6. Since the length of the hot side electrode 11 can be shortened and the total area of the electrode 11 connected to the hot side terminal 1 can be minimized, the influence of unnecessary waves oscillated by an electric field formed in the thickness direction of the base can be suppressed. Consequently, ripples generated on the filter characteristics in the band can be suppressed to a low level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface acoustic wave filter, and particularly to a surface acoustic wave filter in which weighting is provided with interdigital electrodes.

[Conventional technology]

As shown in FIG. 2, a conventional surface acoustic wave filter includes weighted interdigital electrodes 21, 24 on a piezoelectric substrate
It has a structure in which the two are arranged in parallel in the length direction, and the intersection part 8 of the two
The amount of weighting is set based on the size of 1 to S7. The interdigital electrodes 21.24 are each connected to a busbar 12.13 connected to the hot side terminal 1, the installation.

[Problem to be solved by the invention]

In the conventional surface acoustic wave filter described above, the intersection portions 81 to
S7 is distributed near the center between the bus bars 12 and 13, and the hot-side interdigital electrode 21 must be extended and disposed there, and the total area of the interdigital electrode 21 becomes large.
Along with this, there is a drawback that the influence of unnecessary waves excited by the electric field in the thickness direction of the substrate increases, causing ripples in the filter characteristics within the band.

[Means to solve the problem]

The filter of the present invention is a surface acoustic wave filter having a pair of busbars connected to weighted interdigitated electrodes on a piezoelectric substrate, in which each intersecting portion of the intersecting fingers ta representing the weighting ratio is , has a tank bottom disposed close to one of the pair of bus bars connected to the bot side terminal.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a plan view of one embodiment of the present invention. The weighting of the weighted interdigitated electrodes 11, 14 on the piezoelectric substrate represents the amount of intersections S1 to S6, which are connected to the hot side terminal l.
The interdigitated electrodes 14 connected to the grounded buspar 13 are arranged to extend to the intersecting portions 81 to S6. By arranging them in this way, the length of the hot-side interdigitated electrode 11 can be made shorter than in the past. Therefore, the total area of the interdigitated electrodes 1 connected to the hot side terminals 1 can be minimized, and the influence of unnecessary waves excited by the electric field in the thickness direction of the substrate can be suppressed more than before.

〔Effect of the invention〕

As explained above, in the present invention, the total area of the cross-finger electrodes connected to the hot terminal can be minimized by arranging each cross section of the weighted cross-finger electrodes close to the hot terminal. Since unnecessary waves excited by the electric field in the thickness direction of the substrate can be suppressed, ripples within the band can be kept low and a high-performance filter can be realized.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of the present invention, and FIG. 2 is a plan view showing a conventional surface acoustic wave filter. 1...Terminal, 11, 14, 21.24...Cross finger electrode, 12.13...Bus bar, 81-S7...Cross section.

Claims (1)

[Claims] In a surface acoustic wave filter having a pair of busbars in which weighted interdigital electrodes are connected on a piezoelectric substrate, each intersection of the interdigital electrodes representing the weighting ratio is connected to the pair of busbars. A surface acoustic wave filter characterized in that the surface acoustic wave filter is arranged close to one of the terminals connected to the bottom side terminal.