JPH11195908A - Magnetostatic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized magnetostatic wave device that operates in a quasi-microwave band of about 700 MHz to 3 GHz and that is easily impedance-matched with an external high frequency circuit. SOLUTION: The device is provided with a magnetic garnet film 2, a magnetic field generator that applies a magnetic field thereto, an input and/or output transducer of a high frequency signal to/from the magnetic garnet film 2, a transmission line 6 that connects the transducer 3 to an external high frequency circuit 8, and a ground conductor 10 and a capacitive component 16 whose on terminal electrode 16A connects with at least one of the transmission lines 6 and whose other terminal electrode 16B connects with the ground conductor 10. An open stub 19 may connect with the transmission line 6. A chip capacitor whose capacitance is 10 pF or below is used for the capacitive component 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetostatic wave device applied to a magnetostatic wave resonator, a magnetostatic wave filter, or the like.

[0002]

2. Description of the Related Art A magnetostatic wave device has a magnetic garnet film such as YIG, a transducer serving as an electrode for radiating electromagnetic waves to the magnetic garnet film, and a transmission line for supplying a high-frequency signal to the transducer. .
When a microwave signal or a quasi-microwave signal is supplied to the transducer, the electromagnetic wave is converted into a magnetostatic wave and propagates through the magnetic garnet film. Since the frequency of the magnetostatic wave depends on the magnetization of the magnetic garnet film, the magnetostatic wave device can function as a resonator or a filter by controlling the intensity of the external magnetic field applied to the magnetic garnet film.

In the magnetostatic wave device, it is necessary to match impedance with a high-frequency circuit unit for supplying a high-frequency signal in order to reduce insertion loss. Therefore, a proposal has been made to provide a lumped constant circuit element or a distributed constant circuit element between a transducer of a magnetostatic wave device and a high-frequency circuit unit to perform impedance matching.

For example, Japanese Patent Application Laid-Open No. 2-298101 describes a magnetostatic wave element using a distributed constant circuit element as a matching circuit. FIG. 7 shows a configuration example of a magnetostatic wave element described in the publication. The magnetostatic wave element shown in FIG. 7 is obtained by reconstructing the embodiment described in the publication in order to facilitate understanding of the operation. In this magnetostatic wave element, a GGG (gadolinium gallium garnet) substrate 1, a magnetic garnet film 2, and a transducer 3 composed of a grid-like electrode finger are arranged in this order on one main surface of a dielectric substrate 4. And a ground conductor 10 on the other main surface of the dielectric substrate 4. One end of the transducer 3 is connected via a ribbon-shaped conductor 7 to one end of a microstrip line 6 which is a high-frequency transmission line, and the other end of the transducer 3 is connected to a ground conductor 10. The other end of the microstrip line 6 is connected to the high frequency circuit unit 8. Further, a DC magnetic field is applied to the magnetic garnet film 2 perpendicularly to the main surface thereof by a magnetic field generator (not shown).

In this magnetostatic wave element, a part of the microstrip line 6, that is, between the transducer 3 on the magnetic garnet film 2 and the high-frequency circuit unit 8,
A matching stub 9 for impedance matching is provided. The matching stub 9 is a distributed constant circuit element composed of a microstrip line. In the embodiment of the publication, the initial dimension of the matching stub 9 is set to a length L = 2 m.
m, width W = 2 mm, and impedance matching is performed by cutting the length L. In this embodiment, the resonance frequency obtained by adjusting the matching stub is 4 ± 0.5 GHz.
It is. In order to adapt the magnetostatic wave element of this embodiment to a quasi-microwave band of about 700 MHz to 3 GHz, it is necessary to make the matching stub 9 larger than the above-mentioned size. For example,
A matching stub with a characteristic impedance of 50Ω formed on a dielectric substrate having a dielectric constant of about 2 has a length L of about 6 mm when applied to a quasi-microwave band (eg, about 2 GHz).
A large dimension of about W = 2 mm is required.

For example, Japanese Patent Laid-Open No. 4-105401 discloses a magnetostatic wave filter in which a lumped constant circuit element such as a coil and a capacitor and a distributed constant circuit element are provided in a portion where a YIG film is not provided. It describes that impedance matching is performed. FIG. 8 shows a configuration example of a magnetostatic wave filter described in the publication. The magnetostatic wave filter shown in FIG. 8 is obtained by reconstructing the embodiment described in the publication in order to facilitate understanding of the operation. In this magnetostatic wave filter, an input transducer 3a and an output transducer 3b are provided on one main surface of a dielectric substrate 4, and a ground conductor 10 is provided on the other main surface of the dielectric substrate 4. Have been. Input side transducer 3a
Is connected to one end of the input side microstrip line 6a, one end of the output side transducer 3b is connected to the output side microstrip line 6b, and the other end of each transducer is grounded. The GGG substrate 1 provided with the magnetic garnet film 2 on its surface is arranged so that the magnetic garnet film 2 faces both transducers.

In this magnetostatic wave filter, a matching circuit 13 is provided on a part of the input microstrip line 6a, and a matching circuit 14 is provided on a part of the output microstrip line 6b. These matching circuits 13 and 14
Is a distributed constant circuit element formed by widening a part of the input side and output side microstrip lines (width 0.6 mm), similarly to the matching stub 9 shown in FIG. Input-side matching circuit 13 and output-side matching circuit 14
Are symmetrical, and each has a structure in which a rectangular conductor film having a width of 1.7 mm and a length of 7.6 mm is joined to a rectangular conductor film having a width of 0.6 mm and a length of 4.48 mm. However, since the center frequency of the magnetostatic wave filter is 3.8 GHz, the matching circuits 13 and 14 need to be large in order to set the center frequency in a quasi-microwave band of about 700 MHz to 3 GHz.

This publication does not disclose a specific example of a matching circuit using lumped constant circuit elements such as coils and capacitors.

[0009]

As described above, 4GH
Conventionally, magnetostatic wave devices with an operating frequency of about z or higher
Distributed impedance circuit elements are used for impedance matching. However, there is a problem that a magnetostatic wave element using a distributed constant circuit element becomes large when applied to a quasi-microwave band. On the other hand, there is no specific example in which the impedance matching of the magnetostatic wave device is realized by the lumped constant circuit element. It is completely unknown. Further, lumped constant circuit elements such as capacitors have discrete parameters that can be taken, so that fine adjustment of impedance is difficult. For example, when using a capacitor for impedance adjustment,
Since a plurality of capacitors having different capacities are prepared in advance and an optimum capacity is selected from these, it is difficult in terms of cost to exactly match the impedance. However, means for solving such a problem in the lumped constant circuit element has not been proposed conventionally.

An object of the present invention is to enable operation in a quasi-microwave band of about 700 MHz to 3 GHz, in particular, a low frequency band of 800 MHz to 2 GHz, to facilitate impedance matching with an external high-frequency circuit, and to reduce the size. It is to provide a magnetostatic wave device, more specifically, a specific structure of an impedance matching element in such a magnetostatic wave element, and
The purpose is to provide the parameters of this impedance matching element.

[0011]

The above object is achieved by the following (1).
This is achieved by any one of the constitutions (1) to (4). (1) A magnetic garnet film, a magnetic field generator for applying a magnetic field to the magnetic garnet film, a transducer for inputting and / or outputting a high-frequency signal to the magnetic garnet film, and the transducer and an external high-frequency circuit And a transmission line for electrically connecting the device and a ground conductor, wherein one terminal electrode is electrically connected to at least one of the transmission lines,
A magnetostatic wave device having a capacitive element having the other terminal electrode electrically connected to the ground conductor. (2) The magnetostatic wave device according to (1), wherein an open stub is electrically connected to the transmission line. (3) The magnetostatic wave device according to (1) or (2), which is used in a frequency band of 700 MHz to 3 GHz. (4) The magnetostatic wave device according to any one of (1) to (3), wherein the capacitive element is a chip capacitor having a capacitance of 10 pF or less.

[0012]

According to the present invention, in order to efficiently exchange high-frequency signals mainly in the quasi-microwave band with the magnetostatic wave device, a part of a transmission line connecting the external high-frequency circuit unit and the magnetostatic wave device is provided. A capacitive element is provided as an impedance matching element. Unlike a distributed constant circuit element such as the above-described matching stub, the capacitive element does not become large even when used for impedance matching in a low frequency band. Therefore, according to the present invention, a small magnetostatic wave device operating in the quasi-microwave band is realized. In addition, if a chip capacitor having the above-described capacitance is used as a capacitive element, impedance matching with an external high-frequency circuit unit in the quasi-microwave band becomes easy.

Further, if an open stub is connected to the transmission line to which the above-mentioned capacitive element is connected, it is possible to compensate for the disadvantage of the capacitive element in which fine adjustment of the impedance is difficult. Although this open stub is a distributed constant circuit element, it is intended to compensate for the lack of matching by the capacitive element, so unlike the conventional configuration in which impedance matching is performed only with the stub, when applied to the quasi-microwave band However, the size of the open stub does not increase.

Therefore, if the present invention is applied to, for example, a magnetostatic wave filter, a low insertion loss filter with impedance matching in the quasi-microwave band can be easily realized without increasing the size.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Configuration I As a configuration example of a magnetostatic wave device of the present invention, FIG. 1 shows a plan view of an example of a magnetostatic wave resonator. Also, FIG. 2 shows the AA of FIG.
FIG.

The magnetostatic wave device comprises a magnetostatic wave resonator chip 5
1, a magnetic field generator for applying a magnetic field to the magnetostatic wave resonator chip 51, and a dielectric substrate 4. The dielectric substrate 4 has a microstrip line 6 on one main surface.
However, a ground conductor 10 is formed on the other main surface.

The magnetostatic wave resonator chip 51 has a magnetic garnet film 2 on a GGG substrate 1 made of non-magnetic garnet.
And the transducer 3 are formed in this order, and are cut out with a dicing saw. The magnetic garnet film 2 is obtained by shaping a YIG film formed by, for example, an LPE (liquid phase epitaxial) method into a rectangular shape by a photolithography technique or the like.
The transducer 3 is a conductive metal film serving as an input / output transmission line, and is made of Al, Cu, Au, Ag, or the like.

The magnetic garnet film 2 is formed by a pair of magnetic poles 111a and 111b sandwiching the magnetostatic wave resonator chip 51.
A DC magnetic field Hex perpendicular to the main surface is applied.

1 and 2, only the magnetic poles 111a and 111b are shown as elements constituting the magnetic field generator. In addition to these magnetic poles, the magnetic field generator usually includes a yoke connected to each magnetic pole, And a coil for changing the strength of the magnetic field.
FIG. 1 is a plan view showing a state where the magnetic pole 111b is removed.

On the surfaces and side surfaces of the magnetic poles 111a and 111b, a conductor film continuous with the ground conductor 10 is formed. This conductor film is usually composed of a plating film of Au, Ag, Cu or the like.

One end of the microstrip line 6 provided on one main surface of the dielectric substrate 4 is connected to one end of the transducer 3 via a ribbon-shaped conductor 7 made of Au or the like, and the other end is connected to the outside. It is connected to the high frequency circuit unit 8. The other end of the transducer 3 is connected to the magnetic pole 1.
11a through a conductor film formed on the surface of the ground conductor 10a.
It is connected to the.

This magnetostatic wave device has a chip capacitor 16 as a matching circuit composed of lumped constant circuit elements.
The chip capacitor 16 has one terminal electrode 16A adhered to the microstrip line 6 and the other terminal electrode 1A.
6B is connected to the ground conductor 10.

An oscillator circuit is connected to the magnetostatic wave device as the external high-frequency circuit unit 8 to form a magnetostatic wave oscillator. In order to operate the magnetostatic wave oscillator in a quasi-microwave band, the impedance of the external high-frequency circuit unit 8 and the magnetostatic wave device It is sufficient that the frequency matching the impedance is within the quasi-microwave band.

The specific evaluation of the impedance matching between the magnetostatic wave device having this configuration and the external high-frequency circuit was performed according to the procedure described below.

As the magnetostatic wave device, a sample A and a sample B having the following configurations were used. In sample A, the thickness of the magnetic garnet film 2 was 20 μm, and the width of the transducer 3 was 320 μm.
μm, and the thickness of the GGG substrate 1 was adjusted to 95 μm by polishing. In sample B, the thickness of the magnetic garnet film 2 was 35 μm
And the width of the transducer 3 is 130 μm,
The thickness of the G substrate 1 was reduced to 50 μm by polishing. In both samples, the magnetic garnet film 2 has a saturation magnetization of 700
G, a plane dimension of 1 mm × 1 mm is used, the distance between the magnetic pole face 111a and the magnetic pole face 111b sandwiching the magnetic garnet film 2 is about 250 μm, and the transducer 3 is made of Au / Cu.
/ Au / Cr. Then, a chip capacitor 16 was connected to each sample. Chip capacitors have capacitances of 1pF, 3pF, 4pF, 5pF, 7
Those having pF, 9 pF or 11 pF were used. The measurement was also performed without connecting a chip capacitor.

Each sample was connected to an input / output port of a network analyzer instead of the external high-frequency circuit 8 shown. Then, the reflection characteristic S11 is measured, and S1 due to resonance is measured.
The intensity of the DC magnetic field Hex was adjusted so that the signal absorption peak (resonance absorption peak) of the sample No. 1 became maximum, that is, the input impedance of the network analyzer and the impedance of the magnetostatic wave device matched. FIG. 3 shows the relationship between the frequency at which the resonance absorption peak becomes maximum (the resonance frequency at the time of matching) and the capacitance of the chip capacitor 16.

From FIG. 3, it can be seen that the frequency of the maximum resonance absorption peak point is reduced by about 270 MHz (sample A) or about 20 MHz (sample B) at the maximum just by changing the capacitance of the chip capacitor 16 by at least 0.1 pF. . Further, with the increase in the capacity of the chip capacitor 16, the sample B
It can be seen that the resonance frequency at the time of matching always shifts to the lower frequency side in the range of about pF and about 10 pF in sample A. Therefore, a matching circuit using a chip capacitor as a lumped constant circuit element is selected, and the capacitance of the chip capacitor is 10 pF or less, preferably 0.1 to 1 pF.
By selecting from the range of 0 pF, a magnetostatic wave device capable of operating at any frequency in the quasi-microwave band is realized.

However, if the sample B has a capacitance exceeding 3 pF and the sample A has a capacitance exceeding 7 pF, the resonance absorption peak at S11 of the resonator composed of the induction component of the transducer 3 and the capacitance component of the chip capacitor 16 becomes: Since the resonance frequency is generated near the resonance frequency of the magnetostatic wave resonator chip 51 and the resonance frequency at the time of matching does not decrease, it is more preferable to select the capacitance of the chip capacitor from the range of 7 pF or less.

Configuration II FIG. 4 shows another configuration example of the magnetostatic wave device of the present invention. This magnetostatic wave device is obtained by providing an open stub 19 in the magnetostatic wave device shown in FIG. The open stub is a distributed constant circuit element also called an open-end distributed line, one end of which is electrically connected to a transmission line and the other end of which is open. The illustrated open stub 19 is made of a conductor having a microstrip line structure, one end of which is connected to the microstrip line 6, and functions as an impedance matching element together with the capacitive element (chip capacitor 16).

In the above configuration I, when the capacitive element prepared for impedance matching cannot perform sufficient impedance matching, the provision of the open stub 19 enables fine adjustment of the impedance. It can be carried out. Fine adjustment of the impedance is usually performed by shaving an open stub to reduce the area when manufacturing a magnetostatic wave device.

The magnetostatic wave device shown in FIG. 4 has the same configuration as the magnetostatic wave device shown in FIG.

The specific evaluation of the impedance matching between the magnetostatic wave device having this configuration and the external high-frequency circuit was performed according to the procedure described below.

The magnetostatic wave devices prepared are the above-mentioned sample A as a comparative example having no open stub and a sample C having this sample A provided with an open stub. The chip capacitors connected to the sample A have a capacitance of 0.5 pF, 1.
5pF, 3pF, 4pF, 5pF, 7pF or 9pF were prepared. The measurement was also performed without connecting a chip capacitor. On the other hand, no chip capacitor was connected to the sample C, and the width W was adjusted so that the characteristic impedance became 50Ω.
Provided an open stub of 2 mm and its length L was 1 mm,
The measurements were made as mm, 3 mm, 3.8 mm, 4.6 mm, 5.5 mm or 6 mm. The dielectric constant of the dielectric substrate provided with the transmission line and the open stub on the surface is about 2.

The resonance frequency at the time of matching when each capacitor is connected to the sample A, and the length L of the open stub of the sample C
And the resonance frequency at the time of matching when the above was set to the above dimensions, were measured in the same manner as in the case of the above-described configuration I. FIG. 5 shows the results. The resonance frequency of both samples shown in FIG. 5 is the resonance frequency of sample A, that is, without connecting a chip capacitor.
This is a value normalized by the resonance frequency when no open stub is provided. The horizontal axis of the graph shown in FIG.
Is the capacity of the chip capacitor, and the length of the open stub is L for the sample C.

From FIG. 5, the length L of the open stub is 3 mm.
It can be seen that by adjusting within the following range, the same impedance adjustment as when a chip capacitor having a capacitance of about 0.4 pF or less is connected can be performed. That is, in this configuration in which the impedance is finely adjusted by grinding the open stub, the impedance can be strictly adjusted only by preparing chip capacitors having different capacities at relatively coarse intervals of, for example, about 0.4 pF. JP-A-2-29
In the configuration described in Japanese Patent Application Laid-Open No. 8101, impedance adjustment is performed only by the matching stub, and therefore, it is necessary to increase the length L of the matching stub to about 6 mm at a frequency of about 2 GHz. Since it is used to assist the capacitive element, the length L of the open stub is, for example, 3 mm.
It can be reduced to the following.

Configuration III FIG. 6 is a perspective view showing another configuration example of the magnetostatic wave device of the present invention. This magnetostatic wave device has a configuration in which an input and an output are separated. This magnetostatic wave device has a magnetostatic wave filter chip 52, an input side microstrip line 6a, and an output side microstrip line 6b on one main surface of a dielectric substrate 4, and the other of the dielectric substrate 4 On the main surface of
It has a ground conductor 10.

The magnetostatic wave filter chip 52 has a magnetic garnet film 2 provided on a GGG substrate 1.
An input transducer 3a and an output transducer 3b are provided above.

The input side microstrip line 6a is
One end is connected to one end of the input-side transducer 3a via the ribbon-shaped conductor 7a, and the other end is connected to the output side of the external high-frequency circuit unit 8. The output-side microstrip line 6b has one end connected to one end of the output-side transducer 3b via the ribbon-shaped conductor 7b, and the other end connected to the input side of the external high-frequency circuit unit 8. The other end of each transducer is connected to a ground conductor 1
0.

This magnetostatic wave device has chip capacitors 16 and 26 as a matching circuit composed of lumped constant circuit elements. One chip capacitor 16 has one terminal electrode 16A bonded to the input side microstrip line 6a, and the other terminal electrode 16B connected to the ground conductor 10. The other chip capacitor 26 has one terminal electrode 26A adhered to the output side microstrip line 6b, and the other terminal electrode 26B connected to the ground conductor 10.

In the magnetostatic wave device shown in FIG.
A DC magnetic field is applied perpendicularly to the main surface of the magnetic garnet film 2 by a magnetic field generator (not shown).

If the output impedance and the input impedance of the external high-frequency circuit unit 8 are equal, the capacitance of the chip capacitor 16 and the capacitance of the chip capacitor 26 may be made equal. Are different, the capacitance of the chip capacitor 16 is set so that the input impedance of the magnetostatic wave filter chip 52 matches the output impedance of the external high-frequency circuit unit 8, and the capacitance of the chip capacitor 26 is The output impedance of the external high-frequency circuit unit 52 is set to match the input impedance of the external high-frequency circuit unit 8. By selecting the capacitance of each chip capacitor in this manner, the magnetostatic wave device can be operated as a filter having a small insertion loss.

As described above, the magnetostatic wave device of the present invention can operate in a quasi-microwave band as a magnetostatic wave oscillator or a magnetostatic wave filter, and does not increase in size.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration example of a magnetostatic wave device of the present invention.

FIG. 2 is a sectional view taken along line AA of the magnetostatic wave device of FIG.

FIG. 3 is a graph showing a relationship between a capacitance of a chip capacitor and a resonance frequency of a magnetostatic wave device at the time of impedance matching.

FIG. 4 is a plan view showing a configuration example of a magnetostatic wave device of the present invention.

FIG. 5 is a graph showing the relationship between the capacitance of a chip capacitor and the dimensions of an open stub, and the resonance frequency of a magnetostatic wave device during impedance matching.

FIG. 6 is a perspective view showing a configuration example of a magnetostatic wave device of the present invention.

FIG. 7 is a perspective view showing a configuration of a conventional magnetostatic wave element.

FIG. 8 is a perspective view showing a configuration of a conventional magnetostatic wave filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 GGG board 2 Magnetic garnet film 3 Transducer 3a Input side transducer 3b Output side transducer 4 Dielectric substrate 51 Magnetostatic wave resonator chip 52 Magnetostatic wave filter chip 6 Microstrip line 6a Input side microstrip line 6b Output side microstrip line 7, 7a, 7b Ribbon conductor 8 External high frequency circuit unit 9 Matching stub 10 Ground conductor 111a, 111b Magnetic pole 13 Matching circuit 14 Matching circuit 16, 26 Chip capacitor 16A, 16B, 26A, 26B Terminal electrode 19 Open stub

Claims (4)

[Claims] 1. A magnetic garnet film, a magnetic field generator for applying a magnetic field to the magnetic garnet film, a transducer for inputting and / or outputting a high-frequency signal to and from the magnetic garnet film; A magnetostatic wave device having a transmission line for electrically connecting a high-frequency circuit and a ground conductor, wherein one terminal electrode is electrically connected to at least one of the transmission lines, and the other terminal electrode A magnetostatic wave device having a capacitive element electrically connected to the ground conductor. 2. The magnetostatic wave device according to claim 1, wherein an open stub is electrically connected to said transmission line. 3. The magnetostatic wave device according to claim 1, which is used in a frequency band of 700 MHz to 3 GHz. 4. The magnetostatic wave device according to claim 1, wherein said capacitive element is a chip capacitor having a capacitance of 10 pF or less.