JPS594216A - Surface acoustic wave device - Google Patents

Abstract

PURPOSE:To adjust easily the capacitance formed between plural auxiliary electrodes and an input/output transducer, by grounding a prescribed number of auxiliary electrodes among plural auxiliary electrodes. CONSTITUTION:The auxiliary electrodes 31 forming the transducer and the capacity and short-circuited electrodes 32 short-circuiting the auxiliary electrodes are constituted at the back side of the said piezoelectric substrate 10 in a figure. CX1, CX2 are variable capacitances in the figure and correspond to the auxiliary electrodes 31 and the short-circuited electrodes 32. The operation to vary the capacitance are done by cutting off successively the short-circuited electrodes 32. The CX1, CX2 being the capacitances between the transducer and ground are decreased through such operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a surface acoustic wave device comprising an input/output transducer consisting of interdigitated electrodes disposed on a piezoelectric substrate, and particularly relates to a surface acoustic wave device with guaranteed attenuation Ji' t-Relating to a surface acoustic wave device that can be easily and accurately improved.

(b) Prior art and problems In order to provide a large guaranteed attenuation t in surface acoustic wave devices, especially P-wave devices, etc., it is necessary to suppress electrical leakage waves caused by stray capacitance and mutual induction between input and output. Are known.

Conventionally, there has been a surface acoustic wave device having a structure as shown in FIG. 1 as a surface acoustic wave device that obtains such a large amount of guaranteed attenuation.

Hereinafter, a conventional surface acoustic wave device will be explained using FIG. 1 and FIG. 2.

FIG. 1 shows the configuration of a conventional surface acoustic wave device.

In FIG. 1, 10 is a piezoelectric substrate, 11.21 is a transducer, and 12.13.22.23 is a common electrode.

FIG. 2 is a diagram showing an equivalent circuit of FIG. 1. In the figure, Y is the surface acoustic wave radiation admittance, CI, C
! is the capacitance of the transformer ← capacitance between the crossed finger electrodes), C0 is the stray capacitance between input and output, and L11L! Acupuncture
M indicates self-induction such as a wire, and M indicates mutual induction.

Note that the resistance of lead wires, etc. is omitted in the figure because it is minute.

In the surface acoustic wave device shown in FIG.
Suppresses leakage sound due to stray capacitance.

Alternatively, methods such as suppressing leakage waves due to mutual induction by devising the arrangement have been taken.

The characteristics of such a surface acoustic wave device include a surface acoustic wave radiation admittance Y1, a capacitance C of the Yt1 transducer,
It is determined by the values of C1, stray capacitance C0 between input and output, self-induction L1 of lead wires, LI, and mutual induction M. In particular, when mutual induction M is positive, the attenuation pole waits outside the passband. A particularly large guaranteed attenuation amount is obtained near the attenuation pole.

However, with this configuration method, it is difficult to adjust the guaranteed attenuation after wiring, and in the high frequency range, the guaranteed attenuation is difficult to adjust due to minute differences in capacitance of the transformer and mutual induction between input and output. The disadvantage is that the amount of attenuation varies greatly and uniform characteristics cannot be obtained.

(0) Object of the Invention The entire purpose of the present invention is to provide a surface acoustic wave device that can easily and accurately improve the guaranteed attenuation amount so as to eliminate the drawbacks of the conventional surface acoustic wave devices.

((1) Structure of the Invention In order to achieve the above object, the present invention provides a surface acoustic wave device in which an input/output transducer consisting of crossed electrodes is disposed on a piezoelectric substrate. A plurality of auxiliary electrodes are provided on the surface or the input/output transducer mounting surface of the piezoelectric substrate, and a predetermined number of auxiliary electrodes among the plurality of auxiliary electrodes are grounded, thereby creating a connection between the auxiliary electrode and the input/output transducer. (e) Embodiments of the Invention Hereinafter, embodiments of the surface acoustic wave device of the present invention will be explained with reference to all drawings. The figure shows an embodiment of the surface acoustic wave device of the present invention. In this figure, the same parts as in FIG. 1 are given the same numbers.

Auxiliary electrode 31 for forming transducer and full capacitance
A short-circuit II pole 32 that short-circuits the auxiliary electrode and the auxiliary electrode is shown on the back side of the piezoelectric substrate 10 in FIG.
It is configured on the mounting surface of 0.

FIG. 5 is a diagram showing an equivalent circuit diagram of the embodiment of the present invention shown in FIGS. 3 and 4. FIG. In this figure, CX, , CX are variable capacitors, and correspond to the auxiliary electrode 31 and the short-circuit electrode 32 shown in FIGS. 3 and 4. This variable operation is performed by short-circuiting electrode 3
2 is sequentially cut (in FIG. 3, using a laser or the like that passes through the piezoelectric substrate 10). By this operation, the presence between the transducer and the ground, aXCX shown in FIG. 5, is reduced, and the guaranteed attenuation is improved.

FIG. 6 is a diagram showing attenuation characteristics when the present invention is applied.

In this figure, the broken line (a) shows an example of the characteristics of a surface acoustic wave device having a structure according to the present invention, and the solid line (b) shows an example of the characteristics after appropriately cutting the short-circuit electrode of the surface acoustic wave device. show. In the figure f. indicates the center frequency gold. As shown in the figure, it can be seen that the guaranteed attenuation amount is improved on the high frequency side.

Although the above example has been explained in which the capacitance is decreased, it is also possible to increase the total capacitance to improve the guaranteed attenuation amount on the low frequency side. For example, in the embodiment shown in FIG. 4, there is no shorting electrode 32, and if necessary, the auxiliary electrode 31? If it is connected to the ground with a short circuit (T&) (lead wire connection, etc.), the capacity will increase and the guaranteed attenuation on the low frequency side can be improved.

(f) Effects of the Invention As detailed above, according to the surface acoustic wave device of the present invention, the guaranteed attenuation amount can be easily improved, and when improving the guaranteed attenuation amount, it is easy to improve the guaranteed attenuation amount. The effect of being able to do this is obtained.

[Brief explanation of the drawing]

FIG. 1 shows the configuration of a conventional surface acoustic wave device. FIG. 2 shows an equivalent circuit of the surface acoustic wave device. FIGS. 3 and 4 show an embodiment of the structure according to the present invention. FIG. 5 is an equivalent circuit of the surface acoustic wave device according to the present invention. FIG. 6 shows an example of the characteristics improved on the guaranteed attenuation high frequency side in the surface acoustic wave device according to the present invention. In the figure, 10...Piezoelectric substrate 11.21...Transducer 12.13.
22.23...Common-pole 30...Piezoelectric substrate mounting surface 31...Auxiliary electrode 32...Short-circuit electrode Yi, Yt...・Surface acoustic wave radiation admittance c
o... Stray capacitance between input and output C110!・・・・・・Transducer capacitance L
IXTJ1...Self-guidance M for lead wires, etc.
・Mutual induction between input and output

Claims (1)

[Claims] A collection of input and output quadrature stripes consisting of interdigitated electrodes on a piezoelectric substrate.
In the surface acoustic wave device, a plurality of auxiliary electrodes are provided on the surface of the piezoelectric substrate or on the surface of the input/output transformer of the piezoelectric substrate, and a predetermined portion of the plurality of auxiliary electrodes is provided. By grounding several auxiliary electrodes, a volume is formed between the auxiliary electrodes and the input/output transducer.
A surface acoustic wave device characterized by adjustment.