JPH0559959U - Surface acoustic wave device - Google Patents

Abstract

(57) [Summary] [Structure] At least two surface acoustic wave (SAW) electrodes 2 and 3 having different frequency bands are arranged side by side on one piezoelectric substrate 1 in a direction orthogonal to the SAW propagation direction. By applying a voltage to the electrodes 2 and 3, each SAW propagates in the direction of the arrow on the surface of the piezoelectric substrate 1 without causing mutual interference. [Effect] A one-chip SAW element having two types of characteristics can be obtained, and an apparatus using the SAW element can be reduced in size, weight, and cost.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a surface acoustic wave (hereinafter abbreviated as SAW) element used for signal processing in frequency bands such as VHF and UHF.

[0002]

[Prior Art]

 With the liberalization and personalization of communications worldwide, the technology of mobile radio for individuals has been significantly developed. The wireless device terminals have become smaller and lighter from in-vehicle types to portable types and even pocketable types. In particular, for mobile phones (cellular radio), pagers, etc., there is a strong demand for miniaturization of terminals.

Therefore, conventionally, filters and other components using a semi-coaxial resonator or the like have been replaced with SAW elements.

FIG. 3 is a principle diagram of a conventional SAW element. An RF power supply 12 is supplied to SAW electrodes formed on a piezoelectric substrate 10 at an interval determined by a wavelength λ, that is, an input IDT (Interdigital Transducer) 11. As a result, the SAW is excited, and the SAW propagating at the constant velocity v in the direction indicated by the arrow is received by the opposing output IDT (not shown).

When actually used, as shown in FIG. 4A, a transversal SAW filter is formed by combining an input IDT (positive electrode) 11 and an output IDT (apodized electrode) 13. As shown in (b), a pair of resonators 14 are arranged in the SAW propagation direction to form a resonator-type SAW filter, and the resonator-type SAW filters are selectively used depending on the frequency band range.

FIG. 5 is a typical circuit configuration diagram of a wireless device using a conventional SAW element. In this figure, for example, a plurality of filters R ₁ , R ₂ , IF, etc., each having a different frequency band, are provided with SAW elements. The element is being used.

[0007]

[Problems to be solved by the device]

 However, in the conventional SAW element, the SAW electrode of one frequency band is provided on one substrate, so that a plurality of SAW elements must be used in the circuit configuration shown in FIG. However, there was a limit to the miniaturization and weight saving of radio terminals. However, there is a limit to miniaturization of each SAW element itself.

The present invention has been made in view of the above problems, and provides a SAW element that can be reduced in size and weight by an efficient circuit configuration of a device or an apparatus using the same. The purpose is to

[0009]

[Means for Solving the Problems]

 In the present invention, in order to achieve the above object, a voltage is applied to a SAW electrode on a piezoelectric substrate to generate a SAW having a predetermined frequency, and the SAW is propagated in a specific direction on the substrate surface. At least two SAW electrodes, each having a different frequency band, were arranged in parallel on one piezoelectric substrate in a direction orthogonal to the SAW propagation direction.

[0010]

[Action]

 By arranging a plurality of SAW electrodes in parallel on one piezoelectric substrate and applying a predetermined voltage to these electrodes, a SAW having a frequency corresponding to each electrode pattern is generated. In this case, each SAW affects the substrate only in its propagation direction, and has no effect in the orthogonal direction. Therefore, mutual interference is prevented by arranging the electrodes for SAW side by side in the direction orthogonal to the SAW propagation direction.

[0011]

【Example】

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a principle view of a SAW element according to an embodiment of the present invention, in which two SAW electrodes 2 and 3 having different frequency bands are provided on one piezoelectric substrate (one chip) 1 for SAW. They are arranged side by side in a direction orthogonal to the propagation direction. When a predetermined voltage is applied to these electrodes 2 and 3, a SAW having a frequency corresponding to the electrode pattern is generated and propagates in the direction indicated by the arrow on the substrate 1. In this case, the influence of each SAW on the substrate 1 is only in its propagation direction and there is no influence in the orthogonal direction, so mutual interference of each SAW does not occur.

As a result, a SAW element having a plurality of characteristics can be obtained with one chip. By using this SAW element in a radio terminal, etc., an efficient circuit configuration can be realized and its size and weight can be reduced.

In FIG. 1, two SAW electrodes 2 and 3 are arranged side by side on the substrate 1, but three or more electrodes may be arranged side by side. Further, it is not limited by the type of each electrode, and may be a positive electrode, an apodized electrode, or any other type.

2A and 2B are structural explanatory views of the SAW element according to the present embodiment. FIG. 2A shows a chip structure and FIG. 2B shows an external structure.

First, referring to FIG. 2A, as in the case of FIG. 1, for example, three SAW electrodes 2, 3 and 4 are arranged side by side on one piezoelectric substrate 1, and this is shown in FIG. As shown in b), it is sealed with the package 5. The package 5 may include the outside of the SAW element, IC, etc., so that the influence of external factors such as dust adhesion can be prevented.

[0017]

[Effect of the device]

 As described above, in the present invention, a plurality of SAW electrodes each having a different frequency band are arranged in parallel on one piezoelectric substrate in the direction orthogonal to the SAW propagation direction. It is possible to realize a SAW element that exhibits As a result, the functions of a plurality of SAW elements can be realized by one element, and there is an effect that the elements themselves can be made highly functional.

Moreover, since a plurality of SAW electrodes can be simultaneously formed in one processing step, the man-hours similar to those of the conventional SAW element are sufficient, which is economically advantageous.

By using such a SAW element in a radio terminal, only one part has conventionally used a plurality of SAW elements, which promotes efficient circuit configuration and reduction in size and weight. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a principle view of a SAW device according to an embodiment of the present invention.

FIG. 2 is a structural explanatory view of a SAW element according to an embodiment of the present invention, (a) showing a chip structure and (b) showing an external structure.

FIG. 3 is a principle diagram of a conventional SAW element.

FIG. 4 is a chip structure example of a conventional SAW element,
(A) is a diagram showing an example in the case of a transversal type SAW filter, and (b) is a diagram showing an example in the case of a resonator type SAW filter.

FIG. 5 is a typical circuit configuration diagram of a radio terminal using a conventional SAW element.

[Explanation of symbols]

1, 10 ... Piezoelectric substrate, 2, 3, 4, 11, 13 ... IDT
(SAW electrode), 5 ... Package, 14 ... Resonator.

Claims (1)

[Scope of utility model registration request] 1. A surface acoustic wave element for generating a surface acoustic wave of a predetermined frequency by applying a voltage to a surface acoustic wave electrode on a piezoelectric substrate and propagating the surface acoustic wave in a specific direction on the surface of the substrate. A surface acoustic wave device characterized in that at least two surface acoustic wave electrodes each having a different frequency band are arranged in parallel on a single piezoelectric substrate in a direction orthogonal to the propagation direction of the surface acoustic wave.