JPH04360309A - Composite element - Google Patents

Abstract

PURPOSE:To attain the modulation based on the mechanical coupling by providing a surface acoustic wave resonator to a front and a rear side of a very thin quartz substrate so as to be opposite to each other. CONSTITUTION:A surface acoustic wave resonator 8 is formed on the front side of a flat quartz substrate 2 by forming interdigitally plural electrodes 4 connecting electrically to each other on the substrate 2 and electrodes 6 of the same number as that of the electrodes 4 connecting electrically to each other on the substrate 2. The electrodes 10, 12 are formed to the rear side of the substrate 2 opposite to the electrodes 4, 6 on the front side respectively to form a surface acoustic wave resonator 14 having a same type of transducer. Thus, both the elements are coupled mechanically, and the modulation that a natural frequency (resonance frequency or the like) of one element is set to a carrier frequency and a natural frequency of the other element is set to a modulation frequency is attained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite element formed by combining a surface acoustic wave resonator and a surface acoustic wave filter.

In the field of electronic equipment, resonators and filter elements that use surface acoustic waves propagating through the surface layer of a crystal substrate are sometimes used to obtain signals of a constant frequency. These surface acoustic wave resonators or surface acoustic wave filters are generally used when handling high frequency signals, but in reality they are used differently depending on the purpose. It would be convenient if these elements could be combined in a specific configuration to achieve entirely new functionality.

0003

[Prior Art] Conventionally, surface acoustic wave resonators have been known in which comb-shaped electrodes are provided on a crystal substrate to excite Rayleigh waves or SH (shear horizontal) waves in the surface layer of the crystal substrate. ing.

[0004] Furthermore, as a surface acoustic wave filter, a pair of comb-shaped electrodes are provided on a crystal substrate so that the propagation directions of the excited surface acoustic waves coincide, and a pair of comb-like electrodes is provided on a crystal substrate so as to similarly excite Rayleigh waves or SH waves. It is known what has been done.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite element that can be applied to completely new uses. Specifically, the purpose is to provide a composite element capable of modulation based on mechanical coupling.

[0006]

[Means for solving the problem] The technical problem mentioned above is
This problem is solved by any one of the first to third configurations of the present invention.

[0007] In the first configuration of the composite element of the present invention, surface acoustic wave resonators are configured on the front and back surfaces of an extremely thin crystal substrate so as to face each other.

[0008] In a second configuration of the composite element of the present invention, surface acoustic wave filters are configured on the front and back surfaces of an extremely thin crystal substrate so as to face each other.

A third configuration of the composite element of the present invention is one in which a surface acoustic wave resonator and a surface acoustic wave filter are configured to face each other on the front and back surfaces of an extremely thin crystal substrate.

0010

[Operation] According to any one of the first to third configurations of the composite element of the present invention, since a pair of elements are provided on the front and back surfaces of an extremely thin crystal substrate so as to face each other, there is a mechanical gap between the two elements. This makes it possible to perform modulation in which the natural frequency (resonant frequency, etc.) of one element is the carrier wave frequency, and the natural frequency of the other element is the modulating wave frequency. Realization becomes possible.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a first configuration of a composite element of the present invention. 2 is a flat crystal substrate, and on the front side of this crystal substrate 2, there are a plurality of electrode fingers 4 that are electrically connected on the crystal substrate, and the same number of electrode fingers 4 that are electrically connected on the crystal substrate. A surface acoustic wave resonator 8 is constructed by alternately forming electrode fingers 6 that are connected to each other.

The electrode fingers 4 and 6 are constructed in a so-called IDT (interdigital transducer) type. That is, the width of the electrode fingers 4, 6 and the interval between the electrode fingers 4, 6 are equal, and the value thereof is 1/4 of the wavelength of the excited surface acoustic wave.

The arrangement direction of the electrode fingers 4 and 6 is set at a predetermined angle with respect to the crystal axis direction of the crystal substrate depending on the type of surface acoustic wave (Rayleigh wave, SH wave) to be excited. Ru.

Electrode fingers 10 and 12 are formed on the back side of the crystal substrate 2 to face the electrode fingers 4 and 6 on the front side, respectively, and a surface acoustic wave resonator 14 having an IDT type transducer is also formed. It is configured.

Reference numeral 16 indicates a positive terminal of the surface acoustic wave resonator 8 to which the electrode finger 4 is connected, and reference numeral 18 indicates a negative terminal of the surface acoustic wave resonator 8 to which the electrode finger 6 is connected. Also, 20
22 is a positive terminal of the surface acoustic wave resonator 14 to which the electrode finger 12 is connected, and 22 is a negative terminal of the surface acoustic wave resonator 14 to which the electrode finger 10 is connected.

According to this configuration, since the surface acoustic wave resonators are configured to face each other on the front and back surfaces of the extremely thin crystal substrate, modulation based on mechanical coupling between the two becomes possible. That is, for example, one surface acoustic wave resonator 8
By configuring a carrier wave circuit including the surface acoustic wave resonator 14 and configuring a modulation circuit including the other surface acoustic wave resonator 14,
A modulation signal is superimposed on a carrier wave by mechanical coupling, and a modulation circuit device with a simple configuration can be provided.

In this embodiment, the electrode fingers on the front side and the back side of the crystal substrate are arranged to face each other, and the corresponding electrode fingers have opposite polarity, but this is done in order to increase the modulation efficiency. It is. The present invention can also be practiced without the electrode fingers facing each other.

High modulation efficiency can be obtained by matching the thickness of the crystal substrate 2 to the thickness of the thickness-shear oscillator that can be excited at the frequency of one surface acoustic wave resonator. That is, when the thickness of the crystal substrate is t and the resonant frequency is f, the condition for excitation of the thickness-shear oscillator is t=
Since it is expressed as a(2n-1)/f (a is a constant and n is a natural number), efficient modulation is possible by setting the thickness of the crystal substrate that satisfies this condition. .

FIG. 2 is a diagram showing another embodiment of the first configuration of the composite element of the present invention. In this embodiment, a surface acoustic wave resonator 8 configured on the front side of the crystal substrate 2 and a surface acoustic wave resonator 8 configured on the surface side of the crystal substrate 2
A surface acoustic wave resonator 14 configured on the back side of the resonator is connected in parallel.

In this case, the electrode fingers 6 and 12 are grounded, and the terminal 16 to which the electrode finger 4 is connected is used as an input terminal.
By using the terminal 22 to which the electrode finger 10 is connected as an output terminal, a filter suitable for miniaturization can be provided.

In this embodiment, by setting the thickness of the crystal substrate 2 so as to satisfy the excitation conditions described above, the mechanical coupling efficiency can be increased and a filter with a wide band can be provided. become.

FIG. 3 is a diagram showing an embodiment of the second configuration of the composite element of the present invention. In this embodiment, surface acoustic wave filters 2 are placed on the front and back surfaces of the crystal substrate 2 so as to face each other.
4,26.

That is, electrode fingers 4 are provided on the surface side of the crystal substrate 2.
A surface acoustic wave resonator 8A in which electrode fingers 4B and 6A are alternately provided, and a surface acoustic wave resonator 8 in which electrode fingers 4B and 6B are alternately provided.
B constitutes a surface acoustic wave filter 24 consisting of a surface acoustic wave resonator 14A having electrode fingers 10A and 12A alternately provided on the back side of the crystal substrate 2, and a surface acoustic wave resonator 14A having electrode fingers 10B and 12B provided alternately.
A surface acoustic wave filter 26 is constituted by surface acoustic wave resonators 14B which are alternately provided.

16A and 18A are surface acoustic wave filters 24
16B, 18B are the output side terminals of the surface acoustic wave filter 24, 20A, 22A are the input (output) side terminals of the surface acoustic wave filter 26, 20B, 22B are the outputs of the surface acoustic wave filter 26. (input) side terminal.

According to this configuration, both filters 24 and 26
Modulation based on mechanical coupling becomes possible. That is, for example, by configuring a carrier wave circuit including the surface acoustic wave filter 24 and configuring a modulation circuit including the surface acoustic wave filter 26, a modulation signal can be superimposed on the carrier wave by mechanical coupling. In this way, according to this embodiment, a modulation circuit device with a simple configuration can be provided.

In this case, by setting the thickness of the crystal substrate 2 so as to satisfy the excitation possible conditions described above,
It is possible to increase modulation efficiency.

FIG. 4 is a diagram showing another embodiment of the second configuration of the composite element of the present invention. In this embodiment, in the configuration shown in FIG. 3, a surface acoustic wave filter 24 on the front side of the crystal substrate 2 and a surface acoustic wave filter 26 on the back side of the crystal substrate 2 are connected in series.

That is, by connecting the terminal 16B and the terminal 20B,
By connecting the terminals 18B and 22B and grounding the terminals 18A and 22A, it is possible to provide a filter that is suitable for miniaturization and uses the terminal 16A as an input terminal and the terminal 20A as an output terminal.

In this case, by making the frequency characteristics of the surface acoustic wave filters 24 and 26 formed on the front and back sides of the crystal substrate substantially the same, it is possible to provide a filter with good attenuation characteristics. Additionally, by setting the thickness of the crystal substrate 2 so as to satisfy the above-mentioned excitation possible conditions, it is possible to provide a filter with low loss.

FIG. 5 is a diagram showing still another embodiment of the second configuration of the composite element of the present invention. In this embodiment, surface acoustic wave filters 24 and 26 formed on the front and back sides of the crystal substrate 2 are connected in parallel.

That is, the terminals 16A and 20A are connected, the terminals 18A and 22A are connected, the terminals 16B and 20B are connected, and the terminals 18B and 22B are connected.
2A and 22B are grounded.

According to this configuration, it is possible to provide a filter that is suitable for miniaturization and uses the terminal 16A as an input terminal and the terminal 16B as an output terminal. In this case, it is possible to obtain a characteristic in which the characteristics of the two surface acoustic wave filters are combined, so that it becomes easy to provide a filter with a broadband frequency characteristic, for example.

In this embodiment as well, by setting the thickness of the crystal substrate 2 so as to satisfy the excitation conditions described above, a filter with low loss can be provided.

FIG. 6 is a diagram showing an embodiment of the third configuration of the composite element of the present invention. In this embodiment, a surface acoustic wave filter 24 is formed on the front side of the crystal substrate 2, and a surface acoustic wave resonator 14 is formed on the back side of the crystal substrate 2.

According to this configuration, modulation based on mechanical coupling between the filter and the resonator becomes possible. For example, by configuring a carrier wave circuit including the surface acoustic wave filter 24 and configuring a modulation circuit including the surface acoustic wave resonator 14, it is possible to superimpose a modulation signal on the carrier wave by mechanical coupling. A modulation circuit device having the following configuration can be provided. Furthermore, the passband of the surface acoustic wave filter can also be modulated.

In this embodiment as well, the modulation efficiency can be increased by setting the thickness of the crystal substrate 2 so as to satisfy the excitation conditions described above.

FIG. 7 is a diagram showing another embodiment of the third configuration of the composite element of the present invention. In this embodiment, a surface acoustic wave filter 24 formed on the front side of the crystal substrate 2 and a surface acoustic wave resonator 14 formed on the back side of the crystal substrate 2 are connected in series.

That is, by connecting the terminal 16B and the terminal 20,
Terminal 18A and terminal 18B are grounded.

According to this configuration, it is possible to provide a resonator suitable for miniaturization, in which the terminal 16A is used as an input terminal and the terminal 22 is used as an output terminal. In this case, the surface acoustic wave filter 2
By matching the center frequency of the passband 4 and the resonant frequency of the surface acoustic wave resonator 14, it is possible to realize a high-performance resonator with less spurious.

Furthermore, in this embodiment, by setting the thickness of the crystal substrate 2 so as to satisfy the above-described excitation conditions, it is possible to realize a resonator with low loss.

[0042]

[Effects of the Invention] As explained above, according to the present invention,
This has the effect of making it possible to provide a composite element that can perform modulation based on mechanical coupling.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a first configuration of a composite element of the present invention.

FIG. 2 is a diagram showing another embodiment of the first configuration of the composite element of the present invention.

FIG. 3 is a diagram showing an example of a second configuration of the composite element of the present invention.

FIG. 4 is a diagram showing another embodiment of the second configuration of the composite element of the present invention.

FIG. 5 is a diagram showing still another embodiment of the second configuration of the composite element of the present invention.

FIG. 6 is a diagram showing an example of a third configuration of the composite element of the present invention.

FIG. 7 is a diagram showing another embodiment of the third configuration of the composite element of the present invention.

[Explanation of symbols]

2　Crystal substrate 8,14 Surface acoustic wave resonator 24, 26 Surface acoustic wave filter

Claims (6)

[Claims] 1. A composite element characterized in that surface acoustic wave resonators are arranged on the front and back surfaces of an extremely thin crystal substrate (2) so as to face each other. 2. The composite element according to claim 1, wherein the surface acoustic wave resonators are connected in parallel. 3. Surface acoustic wave filters (24
, 26) A composite element comprising: Claim 4: The surface acoustic wave filter (24, 26
) are connected in series or in parallel. 5. Surface acoustic wave resonators (14) are disposed on the front and back surfaces of an extremely thin crystal substrate (2) so as to face each other.
and a surface acoustic wave filter (24). 6. The composite element according to claim 5, wherein the surface acoustic wave resonator (14) and the surface acoustic wave filter (24) are connected in series.