JP2002368503A - Method for adjusting characteristic for band-pass filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a band-pass filter characteristic adjusting method by which a filter characteristic is easily adjusted over a wide range also a degree of freedom of design is enhanced. SOLUTION: In a band-pass filter, ground electrodes 3 and 4 are formed on the both surfaces of a dielectric substrate 2, a metallic film 5 for constituting a plurality of resonators is partially formed at a certain height position in the dielectric substrate 2, a through-hole 5a is formed as a coupling circuit for coupling the plurality of resonators with the metallic film 5 and input/output electrodes 6 and 7 are connected to the metallic film 5. The filter characteristic is adjusted by changing a distance between the metallic film 5 and the ground electrodes 3 and 4, in the band-pass filter characteristic adjusting method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the characteristics of a band-pass filter used in high-frequency applications such as microwaves and millimeter-wave bands. About.

[0002]

2. Description of the Related Art Conventionally, various types of dual-mode bandpass filters have been proposed as bandpass filters used in a high-frequency region (MINIATURE DUAL MODE MICROS).
TRIP FILTERS, JA Curtis and SJ Fiedziuszko, 19
91 IEEE MTT-S Digest).

FIGS. 11 and 12 are schematic plan views for explaining a conventional dual-mode bandpass filter. In the bandpass filter 200 shown in FIG. 11, a circular conductive film 201 is formed on a dielectric substrate (not shown). The input / output coupling circuit 202 and the input / output coupling circuit 203 are coupled to the conductive film 201 so as to form an angle of 90 ° with each other. The central angle 45 with respect to the portion where the input / output coupling circuit 203 is disposed.
An open-end stub 204 is formed at a position forming an angle of °. As a result, two resonance modes having different resonance frequencies are coupled, and the bandpass filter 200 is configured to operate as a dual mode bandpass filter.

In the dual mode bandpass filter 210 shown in FIG. 12, a substantially square conductive film 211 is formed on a dielectric substrate. In this conductive film 211,
The input / output coupling circuit 21 is formed so as to form an angle of 90 ° with each other.
2,213 are connected. Also, the input / output coupling circuit 2
The corner at 135 ° to 13 is missing. By providing the missing portion 211a, the resonance frequencies of the two resonance modes are made different, and the resonances of the two modes are combined, and the band-pass filter 210
Operate as a dual-mode bandpass filter.

On the other hand, a dual mode filter using an annular conductive film instead of a circular conductive film has also been proposed (JP-A-9-139612, JP-A-9-1626).
No. 10 publication). That is, similarly to the dual mode band-pass filter shown in FIG. 11, the input / output coupling circuit is arranged so as to form a central angle of 90 ° using an annular ring transmission line, and A dual mode filter in which a stub having an open end is provided in a part is disclosed.

[0006] Japanese Patent Application Laid-Open No. 6-112701 discloses a dual mode filter using a similar ring-shaped transmission line. As shown in FIG. 13, in the dual mode filter 221, a ring resonator in which an annular conductive film 222 is formed on a dielectric substrate is configured. Here, for the annular conductive film 222,
Four terminals 223 to 226 are formed so as to form 90 ° with each other. Of the four terminals, two terminals 223 and 224 arranged at a 90 ° angle to each other are coupled to the input / output coupling circuits 227 and 228, and the remaining two terminals 225 and 226 are coupled to each other. It is connected via a feedback circuit 230.

[0007] It is described that the above configuration allows orthogonal mode resonance that is not coupled to each other to occur in a ring resonator composed of one strip line, and that the degree of coupling can be controlled by the feedback circuit 230.

[0008]

In the conventional dual mode bandpass filter shown in FIGS. 11 and 12,
By forming one conductive film pattern, a two-stage bandpass filter can be formed, and thus the size of the bandpass filter can be reduced.

However, in the circular or square conductive film pattern, since the input / output coupling circuit is configured to be coupled at the above-described specific angle, the degree of coupling cannot be increased, and a wide pass band can be obtained. There was a disadvantage that it could not be done.

In the bandpass filter shown in FIG. 11, the conductive film 201 is circular, and in the bandpass filter shown in FIG. 12, the conductive film 211 is limited to a substantially square shape. Therefore, there is a problem that the degree of freedom in design is low.

Also, in a dual mode bandpass filter using a ring resonator as disclosed in JP-A-9-139612 and JP-A-9-162610, it is similarly difficult to increase the degree of coupling. However, there is a problem that the shape of the ring resonator is limited.

On the other hand, in the dual mode filter 221 described in JP-A-6-112701, the degree of coupling is adjusted by using the feedback circuit 230, and a wider band is achieved. However,
In the dual mode filter described in the prior art, the feedback circuit 230 is required, and there is a problem that the circuit configuration is complicated. In addition, the shape of the ring resonator is limited to an annular shape, and there is a problem that the degree of freedom in design is low.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art, to increase the degree of coupling, to easily adjust the degree of coupling, and to easily realize various characteristics. An object of the present invention is to provide a method for adjusting the characteristics of a pass filter.

[0014]

According to the present invention, there is provided a method for adjusting the characteristics of a bandpass filter, comprising the steps of: providing a dielectric substrate having first and second principal surfaces; A plurality of formed resonators, a coupling circuit for coupling the resonator, an input / output circuit unit coupled to the resonator, and face each other via the resonator and the dielectric substrate layer, A method for adjusting characteristics of a band-pass filter including first and second principal surfaces of a dielectric substrate or a ground electrode formed inside a dielectric substrate, wherein a distance between the resonator and the ground electrode is reduced. By changing
A characteristic adjustment method for a band-pass filter, wherein the characteristic is adjusted.

According to a specific aspect of the present invention, the multiple-wave resonator is formed of a single metal film that generates two resonance modes, and a coupling circuit for coupling the two resonance modes is provided. , Through holes provided in the metal film, thereby forming a dual mode bandpass filter.

In another specific aspect of the present invention, ground electrodes are formed on both sides in the height direction of the plurality of resonators via a dielectric substrate layer, respectively. The distance between them is different from the distance between the other ground electrode and the resonator.

Further, in another specific aspect of the present invention, the distance between the resonator and the ground electrode is partially varied, and by changing the distance, the characteristic of the band-pass filter is improved. Can be adjusted over a wider range.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be clarified by describing a specific embodiment of a method for adjusting the characteristics of a bandpass filter of the present invention with reference to the drawings.

FIGS. 1A and 1B are a schematic plan sectional view and a sectional front view showing a bandpass filter whose characteristics are adjusted in the first embodiment of the present invention. The dual-mode bandpass filter 1 used in the present invention includes:
It has a triplate structure. That is, the dual-mode bandpass filter 1 has a size of 2.5 mm × 1.6 mm ×
It has a rectangular plate-shaped dielectric substrate 2 having a thickness of 0.6 mm. In the present embodiment, the dielectric substrate 2 has a relative permittivity of 7 and t
Mg− of an δ = 0.001 (value at 30 GHz)
It is composed of Si-BO-based glass ceramics. However, the dielectric substrate 2 may be made of other ceramic materials, synthetic resins, or the like.

Upper surface 2a and lower surface 2b of the dielectric substrate 2
, Ground electrodes 3 and 4 are formed on the entire surface. On the other hand, a metal film 5 is formed at an intermediate height position of the dielectric substrate 2. In this embodiment, the metal film 5 has a rectangular shape having a size of 1.6 × 1.2 mm so that the center frequency of the bandpass filter is about 22 GHz. A rectangular through-hole 5a of 5 × 0.6 mm is formed. This metal film 5
And two through-holes 5a
Is formed, the two resonance modes propagating in the long side direction and the short side direction of the rectangular metal film 5 are coupled, and the configuration as a dual mode band-pass filter is obtained.

That is, the through-hole 5a is provided to form a coupling circuit according to the present invention. In the dielectric substrate 2, at the height position where the metal film 5 is formed, the input / output electrodes 6, 7 are formed at a predetermined distance from the short edges 5b, 5c of the metal film 5. ing. The input / output electrodes 6 and 7 are capacitively coupled to the metal film 5. That is, the edge 5 on the short side of the metal film 5 of the input / output electrodes 6 and 7
b, 5c, edges 6a, 7a
The input / output electrodes 6 and 7 are capacitively coupled to the metal film 5 by adjusting the distance between the input / output electrodes 6 and 5c. In this embodiment, the distance between the edges 6a, 7a of the input / output electrodes 6, 7 and the edges 5b, 5c of the metal film 5 is set to 40 μm.

The input / output electrodes 6 and 7 extend to a pair of short side surfaces 2c and 2d of the dielectric substrate 2, and extend downward at the side surfaces 2c and 2d. However, the input / output electrodes 6 and 7 need to be electrically separated from the ground electrode 4. Therefore, the input / output electrodes 6, 7
The portions reaching the side surfaces 2c and 2d are not so long as to reach the lower surface 2b of the dielectric substrate 2.

The electrode portions of the input / output electrodes 6 and 7 at the same height as the metal film 5 have a rectangular shape of 0.4 × 0.3 mm. Portions of the input / output electrodes 6 and 7 reaching the side surfaces 2c and 2d of the dielectric substrate 2 are:
The width is 300 μm and the height dimension is 0.2 mm.

The input / output electrodes 6 and 7 are electrically connected to the outside so that an input signal is applied from the input / output electrode 6 and an output is taken out from the input / output electrode 7. In the dielectric substrate 2, via-hole electrodes 8, 9 are formed on both sides of the portion where the input / output electrodes 6, 7 are provided. The via hole electrodes 8 and 9 are formed so as to extend from the upper surface 2 a to the lower surface 2 b of the dielectric substrate 2, and electrically connect the ground electrode 3 and the ground electrode 4.

In the dual mode bandpass filter 1 of the present embodiment, when an input signal is applied from one of the input / output electrodes 6 and 7, the metal film 5 resonates. In this case, resonance propagating in the direction connecting the input / output electrodes 6 and 7, that is, in the long side direction of the metal film 5, and resonance transmitting in the short side direction occur. Since the metal film 5a is formed, the two resonance modes are coupled, and the characteristics as a dual mode bandpass filter can be obtained.

FIG. 2 is a diagram showing the frequency characteristics of the dual-mode bandpass filter. In FIG. 2, the solid line shows the reflection characteristics and the dashed line shows the transmission characteristics. As is clear from FIG. 2, in the dual mode bandpass filter, the two resonance modes generated in the metal film 5 are coupled by the through hole 5a, so that a pass band as a bandpass filter can be obtained.

FIG. 3 shows a case where the above-described through-hole 5a is not provided and the resonance mode propagated in the long side direction is separated from the resonance mode propagated in the short side direction.
3 shows the reflection characteristics of. As is apparent from FIG. 3, a resonance mode indicated by an arrow A and a resonance mode indicated by an arrow B appear. The resonance mode on the low frequency side indicated by arrow A is the resonance transmitted in the long side direction of the metal film 5, and the resonance indicated by arrow B is the resonance transmitted in the short side direction.

The inventor of the present application has the same configuration as the dual mode bandpass filter 1 shown in FIG. 1 except that the structure having the resonance characteristics shown in FIG. 3, that is, the through hole 5a is not provided. In the configured structure, the metal film 5
Of the metal film 5 as a resonator, that is, the degree of coupling with an external line and the unloaded Q value are changed. I checked.

First, only the thickness of the dielectric substrate 2 was changed without changing the position of the metal film 5. That is, the distance between the ground electrode 3 and the metal film 5 and the ground electrode 4
The external Q value and the change of the unloaded Q value of the resonator when the distance between the metal film 5 and the metal film 5 change in the same manner were examined. FIG. 4 shows a change in the unloaded Q value when the thickness of the dielectric substrate 2 is changed in this manner. In FIG. 4,
Of the two resonances shown in FIG. 3, only the results for the resonance mode indicated by arrow A are shown. Although no result is shown for the resonance mode propagated in the short side direction indicated by the arrow B, it has been confirmed that there is a tendency to change similarly to the resonance mode indicated by the arrow A.

As is clear from FIG. 4, as the thickness of the dielectric substrate 2 increases, that is, as the distance between the metal film 5 and the ground electrodes 3 and 4 increases, the unloaded Q
It can be seen that the value increases.

On the other hand, since it is difficult to directly evaluate the external Q value, the strength of the coupling between the external line and the resonator 5 is evaluated instead by the following method. That is, even if the thickness of the dielectric substrate 2 is increased or decreased, the resonance value is adjusted so that the peak value of the reflection loss of the resonator becomes constant, that is, the matching state with the external line becomes constant. The degree of coupling with the vessel was evaluated. The adjustment for keeping the matching state constant was performed by changing the facing distance between the input / output electrodes 6, 7 and the metal film 5 constituting the resonator. FIG. 5 shows a change in the facing distance between the input / output electrodes 6 and 7 and the metal film 5 when the thickness of the dielectric substrate 2 is increased or decreased in this manner.

As is apparent from FIG. 5, as the thickness of the dielectric substrate 2 decreases and the distance between the metal film 5 and the ground electrodes 3 and 4 decreases, the input / output electrodes 6 and 7 and the metal film 5 It can be seen that it is necessary to reduce the facing distance between. That is, as the distance between the metal film 5 and the ground electrodes 3 and 4 becomes smaller, the coupling between the external line and the resonator becomes weaker.
It can be seen that the facing distance between the metal film 7 and the metal film 5 needs to be reduced. Therefore, it can be understood that the external Q value increases by reducing the distance between the metal film 5 and the ground electrodes 3 and 4, and as a result, the load Q increases.

From the results shown in FIGS. 4 and 5, the unloaded Q value of the resonator is increased by increasing the thickness of the dielectric substrate 2 and increasing the distance between the metal film 5 and the ground electrodes 3 and 4. It was confirmed that the no-load Q value was reduced and the load Q value was increased by reducing the load Q value and decreasing the distance between the metal film 5 and the ground electrodes 3 and 4.

As described above, the characteristics of the dual mode bandpass filter 1 when the distance between the metal film 5 and the ground electrodes 3 and 4 was changed were confirmed. As described above, in the dual mode bandpass filter 1 shown in FIG. 1 in which the thickness of the dielectric substrate 2 is 0.6 mm,
Has been obtained. Therefore, except that the thickness of the dielectric substrate 2 is increased from 0.6 mm to 0.8 mm, a dual-mode bandpass filter 1 configured in the same manner as the dual-mode bandpass filter 1 shown in FIG.
A bandpass filter was manufactured and its filter characteristics were measured. FIG. 6 shows the results.

As is apparent from a comparison between FIG. 2 and FIG. 6, the insertion loss is large in the characteristic (the characteristic shown in FIG. 2) when the thickness of the dielectric substrate 2 is 0.6 mm, On the other hand, when the thickness of the dielectric substrate 2 is set to 0.8 mm, as shown in FIG. 7, the insertion loss is small and the band is wide.

The results of FIGS. 2 and 6 are consistent with the results of the above-described change in the thickness of the dielectric substrate 2 in the case of the unloaded Q value and the loaded Q value in the resonator. That is, by changing the distance between the metal film 5 and the ground electrodes 3 and 4, the unloaded Q value and the loaded Q value of the resonator can be changed, and the characteristics of the bandpass filter can be adjusted.

Next, an embodiment in which the position of the metal film 5 in the height direction is changed will be described. Here, the distance between the ground electrode 3 and the metal film 5 is different from the distance between the ground electrode 4 and the metal film 5.

That is, in the band-pass filter 1 shown in FIG. 1, the height direction position of the metal film 5 is set to ± 1 from the center.
It was changed in the range of 00 μm. FIGS. 7 and 8 show a change in the unloaded Q value and a change in the facing distance between the input / output electrodes 6 and 7 and the metal film 5 when the matching state with the external line is constant. The horizontal axis in FIGS. 7 and 8 indicates the height position of the metal film in the dielectric substrate.

As is apparent from FIG. 7, when the position of the metal film 5 is shifted from the center position of the dielectric substrate 2, the unloaded Q value becomes small, and when the same coupling amount is to be obtained, It can be seen that the facing distance between the input / output electrodes 6, 7 and the metal film 5 is reduced. Therefore, by changing the distance between the metal film 5 and the ground electrodes 3 and 4 by changing the position of the metal film 5, the no-load Q value and the load Q value of the resonator can be adjusted. It can be seen that the characteristics of the bandpass filter can be adjusted.

In the present invention, the no-load Q value and the load Q value of the above-described two resonance modes for forming the band-pass filter can be independently adjusted. Such a modification will be described with reference to FIGS.

FIGS. 9A and 9B are diagrams showing the resonance electric field distribution when a resonance mode propagated in the long side direction and a resonance mode propagated in the short side direction occur in the metal film 5. . In FIGS. 9A and 9B, hatched portions are portions where the resonance electric field is strong.

In consideration of the distribution of the resonance electric field shown in FIGS. 9A and 9B, as shown schematically in FIGS. 10A and 10B, the ground electrode 3 and the via hole electrodes 11 and 12 are connected. If the internal electrodes 13 and 14 to be formed are formed so as to face the portion where the resonance electric field is strong, the distribution of the resonance electric field shown in FIG. 9A can be changed. In other words, the formation of the internal electrodes 13 and 14 affects the distribution of the resonance electric field shown in FIG. It turns out that it gets. Although FIG. 10A shows a plane at the height position where the metal film 5 is formed, the positions and shapes where the internal electrodes 13 and 14 located above are formed are indicated by broken lines. Shown schematically.

That is, it is understood that the unloaded Q value and the loaded Q value can be adjusted only for one resonance mode by partially changing the distance between the ground electrode 3 and the metal film 5.

Although the internal electrodes 13 and 14 have a rectangular shape, other shapes may be used as long as they face the portion where the resonance electric field is strong. In the embodiment described above,
Although a dual-mode bandpass filter having a triplate structure has been described, the present invention is not limited to a filter having a triplate structure, and a ground electrode is formed so as to face a resonator with a dielectric substrate layer interposed therebetween. It can be widely applied to the characteristic adjustment of the band-pass filter having the dielectric resonator structure described above.

[0045]

According to the characteristic adjusting method of the present invention, the filter characteristic is adjusted by changing the distance between the resonator and the ground electrode. Therefore, the insertion loss of the band-pass filter and the degree of freedom of the bandwidth characteristics can be increased, and the filter characteristics which cannot be obtained conventionally can be realized.

The plurality of resonators are constituted by one metal film for generating two resonance modes, and a coupling circuit for coupling the two resonance modes is constituted by a through hole provided in the metal film. In this case, by adjusting the position of the metal film provided with the through hole, the height position of the metal film, and the like, the filter characteristics can be adjusted over a wider range, and the band pass can be adjusted. The degree of freedom in designing the filter can be further increased.

When the distance between the resonator and the ground electrode is partially changed, the resonance electric field generated in the resonance mode in which the characteristics are symmetrically adjusted is changed between the resonator and the ground electrode. Since it can be changed by adjusting the distance, the unloaded Q value and the loaded Q value can be adjusted for the resonance mode to be adjusted. For example, the unloaded Q value and the loaded Q value of one of the two resonance modes can be adjusted. Only the value can be adjusted independently. Therefore, it is possible to easily provide a bandpass filter having various filter characteristics.

[Brief description of the drawings]

FIGS. 1A and 1B are a plan cross-sectional view and a front cross-sectional view for explaining a bandpass filter whose characteristics are adjusted in one embodiment of the present invention.

FIG. 2 is a diagram showing frequency characteristics of the dual mode bandpass filter shown in FIG.

FIG. 3 is a diagram for explaining two resonance modes generated in the resonator of the dual mode bandpass filter shown in FIG.

FIG. 4 shows no-load Q when the thickness of a dielectric substrate is changed.
The figure which shows the change of a value.

FIG. 5 is a diagram for explaining a change in an external Q value when the thickness of a dielectric substrate is changed.

FIG. 6 is a diagram illustrating filter characteristics when the thickness of a dielectric substrate is increased to 0.8 mm in the dual mode bandpass filter illustrated in FIG. 1;

FIG. 7 is a diagram showing a change in a no-load Q value when the thickness of a dielectric substrate is set to 0.6 mm and a position in a height direction of a metal film is changed.

FIG. 8 shows the relationship between the input / output electrode and the metal film when the thickness of the dielectric substrate is 0.6 mm, the height direction position of the metal film is changed, and the coupling amount between the external circuit and the resonator is constant. FIG. 5 is a diagram showing a change in the facing distance of FIG.

FIGS. 9A and 9B are diagrams for explaining a resonance electric field distribution when a resonance mode propagated in a long side direction and a short side direction of a metal film occurs.

FIGS. 10A and 10B are dual-mode bandpass filters in which the distance between a ground electrode and a metal film is partially varied in order to adjust characteristics of a resonance mode propagated in a long side direction. FIG. 2 is a schematic plan sectional view and a front sectional view for explaining the method.

FIG. 11 is a schematic plan view showing an example of a conventional dual mode bandpass filter.

FIG. 12 is a schematic plan view showing another example of a conventional dual mode bandpass filter.

FIG. 13 is a schematic plan view showing still another example of a conventional dual mode bandpass filter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Dual mode band pass filter 2 ... Dielectric substrate 2a ... Upper surface (1st main surface) 2b ... Lower surface (2nd main surface) 2c, 2d ... Side surface 3, 4 ... Ground electrode 5 ... Metal film (resonance) 5a: through-hole 6, 7: input / output electrode 11, 12: via-hole electrode 13, 14: internal electrode

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Naotake Okamura 2-26-10 Tenjin, Nagaokakyo-shi, Kyoto F-term in Murata Manufacturing Co., Ltd. (reference) 5J006 HB04 JA01 JA14 LA11

Claims (4)

[Claims] A dielectric substrate having first and second principal surfaces; a plurality of resonators partially formed at a certain height of the dielectric substrate; and a plurality of resonators formed by the plurality of resonators. A coupling circuit for coupling the resonance modes of the above, an input / output circuit unit coupled to the resonator, and a first and a second of the dielectric substrate facing the resonator via a dielectric substrate layer. And a ground electrode formed inside the dielectric substrate, wherein the characteristic is adjusted by changing a distance between the resonator and the ground electrode. A characteristic adjustment method of a band-pass filter, characterized in that: 2. The method according to claim 1, wherein the plurality of resonators are formed of a single metal film that generates two resonance modes, and a coupling circuit that couples the two resonance modes is provided in the metal film. The method for adjusting the characteristics of a band-pass filter according to claim 1, wherein the through-hole is a through hole. 3. A ground electrode is formed on each side of the plurality of resonators in the height direction with a dielectric substrate layer interposed therebetween, and the distance between one ground electrode and the resonator is reduced by the other ground electrode. 3. The method according to claim 1, wherein the distance between the electrode and the resonator is different. 4. The method according to claim 1, wherein a distance between the resonator and a ground electrode is partially changed.
3. The method for adjusting the characteristics of a bandpass filter according to any one of 3.