JPH04355902A - High frequency circuit - Google Patents

Abstract

PURPOSE:To obtain a small high frequency circuit, having high degree of freedom in design, which is a thick film element that can be manufactured easily and usable in a high frequency range. CONSTITUTION:A substrate constituting layer 1 is formed using low temperature fired material, a resonance circuit, containing at least the patterns 4 and 5 of coils L1 and L2 of thick film, capacitors C1 and C2 of thick film, and electrode patterns 2, 3 and 9 are provided on the above-mentioned substrate, and it is used as the high frequency circuit such as the interstage circuit and the like of a high frequency filter element and a high frequency dielectric filter. At this time, the dielectric constant of the substrate in the neighborhood of the coil pattern of the thick film is set at 15 or less.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency filter having a resonant circuit including a coil pattern and a capacitor electrode pattern formed by a thick film method, and a high frequency circuit such as an interstage circuit of a high frequency filter.

0002

2. Description of the Related Art Various filters such as low-pass filters, high-pass filters, band-pass filters, and band-elimination filters are used in transmission systems of various electrical devices.

[0003] In recent years, 100 MHz
There is a need for a filter that can be used in a high frequency band of approximately 300 MHz or higher, particularly in a high frequency band of approximately 300 MHz or higher. Conventional high frequency band filters include distributed resonance filters, SAW
Filters, LC filters, etc. are known.

[0004] Distributed resonance filters utilize the resonance of a dielectric substrate, and if the dielectric constant of the substrate is ε and the resonant wavelength is λ, the size of the substrate needs to be approximately λ/4 and ε1/2. It is said that Therefore, even if a high dielectric constant material is used for the substrate, there is a limit to miniaturization. Further, distributed resonance filters can only be applied to band pass filters and band rejection.

[0005] Since SAW filters are made of single crystal material, they are more complicated to manufacture than filters using ceramic materials (sintered materials). Therefore, the cost becomes high. Adjustment of the filter characteristics depends on the pattern of the comb-shaped electrodes, but the calculation is very complicated and the design takes time. Furthermore, since the comb-shaped electrode is formed using thin film technology, it is more complex and sensitive than thick film technology such as printing. This also increases costs. Furthermore, in the case of a SAW filter, the surface of the filter element actually vibrates, so packaging must take into account the vibration space. Therefore, the component becomes large, especially in the height direction.

On the other hand, an LC filter has a resonant circuit composed of an inductor section and a capacitor section, and if the coil pattern of the inductor section and the electrode pattern of the capacitor section are formed by a thick film method, it is possible to reduce the size. It is easy and easy to manufacture. Furthermore, the LC filter has an extremely high degree of freedom in setting the center frequency, pass band, etc., and can be applied to various filters other than band pass filters and band reduction.

[0007] Substrates on which thick film inductor elements and thick film capacitor elements are formed have conventionally been made of materials with a high dielectric constant. This is especially due to the high Q of the capacitor element. However, when using such a high dielectric constant substrate for thick film LC
When used as a filter substrate, that is, when the inductor conductor (coil) of an LC filter is patterned on the substrate in a helical or spiral shape by a thick film method, the wavelength depends on the dielectric constant of the substrate near the conductor. In addition, since the stray capacitance caused by the coil pattern becomes large, the self-resonant frequency exists on the relatively low frequency side, and it no longer functions as an inductor in the high frequency range.

[0008] For this reason, it is extremely difficult to design packaging for high-frequency low-pass filters and high-pass filters used at frequencies above about 100 MHz.
Above this level, the LC filter is practically inapplicable.

Furthermore, since stray capacitance is generated in the substrate near the inductor conductor depending on the dielectric constant of the substrate, desired frequency characteristics cannot be obtained.

Furthermore, in the high frequency band, the effective resistance of the conductor increases significantly due to the skin effect, so it is necessary to form a thick film pattern using a conductive material with low resistance.
, Cu, and other low-resistance conductive materials, such as low-temperature firing materials, have not been proposed for the substrate of LC filters.

[0011] Furthermore, as an interstage circuit for a dielectric filter such as a λ/4 resonator, one having L and forming an LC ladder circuit is also known. However, since dielectric resonators (dielectric filters) are normally used at 800 to 1000 MHz, the relationship between wavelength and self-resonant frequency poses the same problem as described above.

0012

[Problems to be Solved by the Invention] The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a thick film LC filter that is compact, has a high degree of freedom in design, and is easy to manufacture, and a dielectric filter that can be used for inter-resonator filters. The purpose of this invention is to make thick film interstage circuits, etc. applicable to high frequency bands, and to achieve good frequency characteristics.

[0013]

[Means for Solving the Problems] Such objects are achieved by the present invention as described in (1) to (7) below. (1) A high-frequency circuit in which a resonant circuit including at least a thick-film coil pattern and a thick-film capacitor electrode pattern is provided on a substrate, the substrate being formed of a low-temperature firing material, and a thick-film coil A high frequency circuit characterized in that a substrate near a pattern has a dielectric constant of 15 or less.

(2) The high frequency circuit according to (1) or (2) above, wherein the dielectric constant of the substrate between the electrode patterns of the capacitor section is higher than the dielectric constant of the substrate near the coil pattern.

(3) The above (
The high frequency circuit according to 1) or (2).

(4) The high frequency circuit according to (1) or (2) above, which is used as an interstage circuit of a dielectric resonator of a high frequency filter.

(5) The high frequency circuit according to the above (4), which includes the coil pattern and the capacitor electrode pattern inside the substrate, and has a plurality of pads on the surface for connecting the plurality of dielectric resonators. .

(6) The high frequency circuit according to (5) above, wherein the coil pattern is provided inside the gap between the pads, and the capacitor electrode pattern is provided inside the pad in the thickness direction of the substrate.

(7) The high frequency filter is 100MH
The high frequency circuit according to any one of (3) to (6) above, which is used in a frequency band of z or more.

[0020]

[Operation] In the present invention, a high frequency filter or a dielectric filter (dielectric resonator) having a resonant circuit including a thick film coil pattern and a thick film capacitor electrode pattern on a substrate can be used.
In the interstage circuit for use in the present invention, the dielectric constant of the substrate at least near the thick film coil pattern is set to be 15 or less, preferably 10 or less.

[0021] Therefore, the shift of the self-resonant frequency of the inductor section to the lower frequency side is reduced, allowing use in a high frequency band, and realizing a compact high frequency filter. It is also easy to design and manufacture.

By using a substrate with such a low dielectric constant, the generation of stray capacitance near the inductor conductor can be suppressed, and extremely good frequency characteristics can be obtained.

In addition, in the interstage circuit, self-resonance of the coil,
The effects of wavelength can be suppressed and the functions of the coil can be effectively demonstrated.

In addition, in the present invention, since the substrate is formed of a low-temperature firing material that can be fired at temperatures below about 1000°C, A, which has low resistance but could not be used conventionally due to the low firing temperature, is used.
g, Cu, etc. can be used as conductor materials. Therefore, it is possible to reduce the effects of increased resistance and decreased Q due to the skin effect, which are problems when used in a high frequency band.

Therefore, the high frequency filter of the present invention or the high frequency filter using the interstage circuit of the present invention has a frequency of 100 MHz.
Suitable for high frequency bands above 300
It can be applied to a frequency band from about MHz to about 1 GHz, and good filter characteristics can be obtained.

[0026]

[Specific Structure] The specific structure of the present invention will be explained in detail below.

The high frequency filter included in the high frequency circuit of the present invention, the thick film interstage circuit between the resonators of the dielectric filter, etc. are resonant circuits that include at least a thick film coil pattern and a thick film capacitor electrode pattern. is provided on the substrate and/or inside the substrate.

The dielectric constant of the substrate used in the present invention is 1
It is 5 or less, preferably 10 or less. The reason why the dielectric constant of the substrate is set in such a range is as follows.

In order to prevent the influence of the wavelength of the signal on the inductance section, the length of the conductor constituting the coil pattern needs to be about 1/8 or less, preferably about 1/10 or less of the wavelength. However, the wavelength may be shortened depending on the dielectric constant of the substrate near the conductor forming the coil pattern. Therefore, if a high dielectric constant substrate is used, the influence of the signal wavelength cannot be prevented unless the conductor length is significantly shortened. However, if the conductor length becomes too short, it becomes impossible to obtain the required number of coil turns.

However, if a substrate with a low dielectric constant is used, it is possible to prevent the influence of the signal wavelength without making the conductor length very short, making it easier to form a coil pattern. In the band up to about 1 GHz to which the present invention is applied, the inductance value of the coil does not need to be so large (for example, about 30 nH or less), so the upper limit of the dielectric constant is set to 15 in the present invention.

In addition, by setting the dielectric constant of the substrate to 15 or less, the stray capacitance generated in the substrate near the coil is reduced, so the self-resonance frequency of the coil can be made higher than the operating frequency. Good frequency characteristics can be obtained. Note that the dielectric constant of the substrate is JIS C
The measurement may be performed based on the resonance method using 2141 or a waveguide.

[0032] Although there are no restrictions on the material constituting the substrate, in order to achieve the above dielectric constant and to be able to fire at a low temperature as described later, a composite structure of ceramic aggregate and glass is preferred. preferable.

The content of glass in the substrate is preferably 50% by volume or more, particularly 60 to 70% by volume. When the glass content is less than the above range, it is difficult to form a composite structure, the strength and formability are reduced, and low-temperature firing as described below becomes difficult.

[0034] There is no particular restriction on the ceramic aggregate, and depending on the intended dielectric constant, firing temperature, etc., for example, one or more of alumina, magnesia, spinel, mullite, forsterite, steatite, cordierite, zirconia, etc. can be used. You can select it as appropriate.

[0035] Furthermore, there is no particular restriction on the glass, and glass commonly used as glass frits such as borosilicate glass, lead borosilicate glass, barium borosilicate glass, calcium borosilicate glass, strontium borosilicate glass, zinc borosilicate glass, etc. Among them, lead borosilicate glass, strontium borosilicate glass, etc. are particularly suitable.

The following glass compositions are preferred.

[0037] SiO2: 50-65% by weight, Al2O
3: 5-15% by weight, B2 O3: 8% by weight or less, Ca
1 to 4 of O, SrO, BaO and MgO: 15 to 4
0% by weight, PbO: 30% by weight or less,

[0038] The above composition further includes Bi2 O3
, TiO2, ZrO2, Y2O3, etc., in an amount of 5% by weight or less.

The substrate material containing such ceramic aggregate and glass can be fired at a low temperature, and can be fired at the same time as the coil conductor and capacitor electrode.

There are no particular restrictions on the conductor material of the coil and the electrode material of the capacitor, but according to the present invention, Au, Ag
, Ag--Pd, Cu, Pt, etc., can be used as low-resistance conductive materials that need to be fired at a temperature of about 1000° C. or lower. Among these, 9 Ag or Cu
A content of 5 to 100% by weight is suitable.

[0041] There is no particular restriction on the conductor pattern of the coil.
For example, it may have a spiral shape, a helical shape, or the like. The inductance of the coil can be set to a desired value depending on the number of turns of the coil and the opening area of the coil.

There are no particular restrictions on the electrode pattern of the capacitor, and it may be selected appropriately depending on the purpose. The capacitance of the capacitor can be set to a desired value depending on the electrode area, the distance between the electrodes, the number of laminated electrodes, and the dielectric constant of the substrate.

[0043] The substrate may have a single layer structure or a multilayer structure. Note that when the substrate has a multilayer structure, a substrate having a dielectric constant higher than that of the substrate of the inductor section can be used as the substrate between the electrode patterns of the capacitor section. That is, in the present invention, it is sufficient that the dielectric constant of the substrate at least near the coil is within the above range. In this case, the area of the capacitor electrode pattern can be reduced and the Q can be increased.

However, in order to suppress the generation of stray capacitance, it is preferable that all the substrates have a dielectric constant within the above range. Moreover, the high frequency circuit of the present invention may have a plurality of resonant circuits including coils and capacitors.

The high frequency filter of the present invention is suitable for use as a high frequency filter element. In this case, a substrate having a resonant circuit including a thick-film coil pattern and a capacitor electrode pattern is mounted as an independent element (discrete component) on various circuit boards.

Furthermore, the high frequency filter of the present invention can also be applied to a circuit board. In this case, in addition to resonant circuits including thick film coil patterns and capacitor electrode patterns, various thick film circuit components such as thick film resistors are provided on or within the board, and various discrete components are mounted. You can also. Furthermore, it may be a staged circuit board of a dielectric filter, which will be described later.

[0047] Although there are no particular restrictions on the method of manufacturing the high frequency circuit such as the high frequency filter of the present invention, it is preferable to use the green sheet method.

In the green sheet method, first, a green sheet to be used as a substrate material is prepared.

[0049] The aforementioned substrate constituent materials, that is, ceramic aggregate particles and glass frit, are mixed, a vehicle such as a binder and a solvent is added to this, and these are kneaded to form a paste (slurry), and this paste is used. Then, a predetermined number of green sheets preferably having a thickness of about 0.1 to 1.0 mm are produced by, for example, a doctor blade method, an extrusion method, or the like.

In this case, the particle size of the glass is 0.1 to 5μ.
m, the particle size of the ceramic aggregate particles is 1 to 8 μm
It is preferable that the degree of

Vehicles include binders such as ethyl cellulose, polyvinyl butyral, acrylic resins such as methacrylic resin and butyl methacrylate, solvents such as ethyl cellulose, terpineol, butyl carbitol, and other various dispersants, activators, plasticizers, etc. You may select one from among them as appropriate depending on the purpose.

Next, using a punching machine or a die press, through holes are formed in the green sheet as necessary. Thereafter, a conductive paste is printed on each green sheet to a thickness of about 10 to 30 .mu.m by, for example, screen printing to form a coil conductor and capacitor electrode pattern and fill the through holes.

[0053] Such a conductive paste is preferably produced by mixing the above-mentioned conductive particles and glass frit, adding the same vehicle as above, and kneading these to form a slurry. . Note that the content of the conductive particles is preferably about 80 to 95% by weight. In addition, the average particle size of the conductive particles is 0.01
The thickness is preferably about 5 μm. The thickness of the conductor or electrode after firing is usually about 5 to 20 μm.

Next, the green sheets are stacked one on top of the other and hot pressed at about 40 to 120° C. and about 50 to 1000 kgf/cm 2 to form a green sheet laminate. Next, binder removal treatment, formation of cutting grooves, etc. are performed as necessary.

[0055] Thereafter, the laminate of green sheets printed with the conductor paste is co-fired under the following conditions. The firing temperature is 1000°C or less, preferably 800 to 1000°C.
The temperature is approximately 850 to 900°C, more preferably approximately 850 to 900°C. The firing time is preferably about 1 to 3 hours, and the holding time at the maximum temperature is preferably about 10 to 15 minutes. The firing atmosphere may include air, O2, or an inert gas such as N2, but air is particularly preferred because it is simple and inexpensive. However, when Cu is used as the conductive material, it is preferable to sinter it in an inert gas.

[0056] When an external conductor is provided, an external conductor paste is usually printed and fired after the substrate is fired, but it may also be fired at the same time as the board.

Although the case where the substrate has a multilayer structure has been described above, the same applies to the case where the substrate has a single layer structure. Although it is preferable that the conductor paste is fired at the same time as the substrate green sheet, the conductor paste may be printed or placed on the substrate after the substrate green sheet is fired, and then fired.

The high-frequency filter of the present invention is suitable for any filter that utilizes an LC resonance circuit, such as a high-pass filter, low-pass filter, band-pass filter, and band-elimination filter.

A specific example of the structure of the high frequency filter of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a high frequency bandpass filter, in which figure A is a circuit diagram, figure B is a mounting diagram (front side), and figure C is a mounting diagram (back side).

In the figure, 1 is a printed circuit board (single board), 2
, 3 is a capacitor electrode pattern, 4 and 5 are coil patterns, 9 is a capacitor electrode pattern (common electrode pattern)
shows. Also, C1 and C2 are capacitors, L1,
L2 represents a coil, and M represents mutual inductance.

This example has the circuit configuration shown in Figure A,
A high frequency filter that exhibits bandpass characteristics due to magnetic coupling between coils is mounted on a single printed circuit board.

As shown in Figure A, the circuit of the high frequency filter includes a first parallel resonant circuit (LC resonant circuit) consisting of a coil L1 and a capacitor C1, a coil L2,
A second parallel resonant circuit (LC resonant circuit) consisting of a capacitor C2 is provided, and coils L1 and L2 of both resonant circuits are magnetically coupled (having mutual inductance M).

When a high frequency filter having such a circuit configuration is mounted on a single printed circuit board 1, the result will be as shown in Figs.

On the front surface (one side) of the printed circuit board 1, one electrode pattern 2 of the capacitor C1 and a coil pattern 4 which will become a part of the coil L1 are integrally formed by printing, and the capacitor C2's electrode pattern 2 is integrally formed. One electrode pattern 3 and the coil pattern 5, which becomes a part of the coil L2, are integrally formed by printing. Further, on the back side (the other side), the other electrode pattern 9 of the capacitors C1 and C2 and the coil pattern 4 which becomes a part of the coil L1 are shown.
It is formed integrally with the coil pattern 5 which becomes a part of the coil L2 by printing, and predetermined portions of each pattern on both the front and back surfaces are connected by through holes or the like to form a circuit configuration as shown in FIG.

As shown in FIG. 1, in the case of a magnetic field coupling type filter in which a resonant circuit is provided in parallel on the substrate surface,
The following problems may occur.

[0067] Since the circuit board is a single board, the coils are arranged horizontally and magnetically coupled. Therefore, the insertion loss becomes large in the amplitude characteristics.

(2) Since the LC resonant circuits are arranged horizontally, the size of the filter element becomes large. In particular, when three or more LC resonant circuits are arranged, the bandpass characteristic is 2.
Although this is an improvement over the case where only one filter element is used, the size of the filter element is inevitably increased.

For this reason, it is preferable to have the following configuration.

(1) A resonant section consisting of a capacitor electrode pattern formed of a thick film and a coil pattern connected to the capacitor electrode pattern and formed of a thick film is attached to any layer constituting the multilayer circuit board. A plurality of resonant parts are provided in the stacking direction (vertical direction) of the multilayer circuit board, and the plurality of resonant parts are arranged such that the coil patterns of adjacent resonant parts are magnetically coupled to each other.

That is, as shown in FIGS. 2 to 4, a parallel resonant circuit (LC resonant circuit) of a coil L and a capacitor C is used as a basic resonance part, and this basic resonance part is It is preferable to mount a plurality of them (in the vertical direction) on a multilayer circuit board in a state where they are magnetically coupled to each other.

FIG. 2 is an explanatory diagram of the implementation of the resonance section, FIG. 3 is an explanatory diagram of the implementation of the high frequency filter, and FIG. 4 is an explanatory diagram of the implementation of the high frequency filter (2).
An implementation example of the following is shown below.

In the figure, L is a coil, C is a capacitor, and 10
-1 to 10-3 are each layer of the multilayer circuit board, 11 is a GND pattern, 12 is a capacitor electrode pattern, 13 is a coil pattern, L1 to Ln are coils, C1 to Cn are capacitors, IN is an input terminal, and OUT is an output terminal , 14
15 is a blind through hole, 15 is an electrode, 16 is a doughnut-shaped margin, 17 is a connection portion (a connection portion by a blind through hole), and 18 is a conductor penetration portion.

First, as shown in FIG. 2A, the basic resonance section is constituted by a parallel resonance circuit (LC resonance circuit) consisting of a coil L and a capacitor.

The resonant frequency f0 of this circuit is f0 =
1/2π(LC)1/2. When this resonant section is mounted on a multilayer circuit board, it is patterned as shown in FIG. 2B (exploded plan view), taking into account the passband of the filter.

[0076] The first layer 10-1 of the multilayer circuit board includes G
The ND pattern 11 is formed by printing with a conductor (thick film GND conductor pattern), and the second layer 10-2 includes a capacitor electrode pattern 12 constituting one electrode of the capacitor C and a part of the coil L. Coil pattern 13 that constitutes
is integrally formed by printing with a conductor, and the third layer 10-3 has a capacitor electrode pattern 12 that constitutes the other electrode (GND side electrode in this example) of the capacitor C.
and a coil pattern 13 constituting a part of the coil L are integrally printed and formed using a conductor.

The GND pattern 11 and the capacitor electrode pattern 12 formed on the layer 10-3 connect the connecting portion 17 provided at one end of each pattern to the GND terminal.

Further, the GND pattern 11 constitutes a GND electrode, and when mounted on a multilayer circuit board, it can serve as an electric field shield for the capacitor section.

Resonant section (LC resonant circuit) shown in FIG. 2 above
A circuit of a high frequency filter (band pass filter) in which a plurality of filters are provided and magnetically coupled to each other is as shown in FIG. 3A.

[0080] As the resonance part, each coil L1
and capacitor C1, coil L2 and capacitor C2
, a coil L3, and a capacitor C3... It is composed of a parallel resonant circuit (LC resonant circuit) of a coil Ln and a capacitor Cn, and the coils of adjacent unit circuits are magnetically coupled.

When the circuit shown in FIG. 3A is mounted on a multilayer circuit board, it becomes as shown in FIG. 3B (mounted sectional view).

The first layer 10-1, the second layer 10-2, and the third layer 10-3 are each patterned with the patterns shown in FIG. 2B (forming a thick film pattern).
These are stacked to form a resonant section.

[0083] N such resonant parts are formed in the layers below from the fourth layer 10-4, and the coil patterns 13 in each unit circuit are arranged so that adjacent coils are magnetically coupled. Laminate.

[0084] Due to this lamination, the resonant parts are arranged in the lamination direction (vertical direction) of the multilayer circuit board.

FIG. 4 shows a mounting example (two sets) of a high frequency filter using two of the above-mentioned resonant parts.

In FIG. 4, A is a circuit diagram, B is a mounting cross section, and C is a partially enlarged view (portion a in FIG. 4).

This high frequency filter (band pass filter) uses two unit circuits (L1 C1 resonant circuit and L2 C2 resonant circuit) and is built into a six-layer multilayer circuit board, as shown in Figure A. It is.

As shown in the figure, patterns are formed on each layer constituting the multilayer circuit board by printing in the same manner as in FIG. 3, and the coils of the two resonant parts are magnetically coupled.

More specifically, it is as follows. A GND terminal (GND) and an input terminal (IN) are formed on the top layer 10-0, and a GND pattern 1 is formed on the layer 10-1.
1, and a capacitor electrode pattern 1 is formed on the layer 10-2.
2 and the coil pattern 13 are integrally formed, and the layer 10-3
, capacitor electrode pattern 12 and coil pattern 1
3 is integrally formed.

Then, the capacitor electrode pattern 12 formed on the layer 10-3 and the GND pattern 11 formed on the layer 10-1 are connected to the layer 10-1 using a blind through hole (a through hole whose inside is filled with a conductor) 14. Connect to the GND terminal formed in 1.

Further, the coil patterns 13 formed on the layers 10-2 and 10-3 are connected by blind through holes 14.

Furthermore, layer 10-4 and layer 10-5,
In addition to forming a capacitor electrode pattern 12 and a coil pattern, a GND terminal (GND) and an output terminal (OUT
) to form. In this case as well, the coil pattern 13 formed on the layer 10-4 and the coil pattern 13 formed on the layer 10-5 are connected by the blind through hole 14, and the capacitor electrode pattern 12 formed on the layer 10-5 is connected to the coil pattern 13 formed on the layer 10-4. It is connected to the GND terminal through a blind through hole 14.

[0093] In this way, each pattern formed in layers 10-1 to 10-3 constitutes one resonant section, and
Each pattern formed in 4 and 10-5 constitutes one resonance section. In this case, the coils (coils formed by connecting two coil patterns) of the two resonance parts are arranged so as to be magnetically coupled to each other.

Note that the input terminal IN and the output terminal OU
Connection with T is made as follows. The input terminal IN is connected to the capacitor electrode pattern 12 formed on the layer 10-2, and the output terminal OUT is connected to the capacitor electrode pattern 12 formed on the layer 10-4. At that time, layer 10-
The GND pattern 11 formed in 1 and the capacitor electrode pattern 12 formed in layer 10-5 are connected using a blind through hole, but this is done using a donut-shaped electrode as shown in FIG.

As shown in Figure C, a hole (a part without a conductor) 16 is provided in a part of the capacitor electrode pattern (pattern connected to GND) 12, and a hole (a part without a conductor) 16 is provided inside the hole in a state insulated from the capacitor electrode pattern 12. forming an electrode 15;
The connection is made by a blind through hole 14.

The configuration example shown in FIG. 5 is a modification of the resonant section shown in FIG. 2, and is capable of electric field shielding of the capacitor section and magnetic shielding of the coil section.

In the mounting explanatory diagrams of FIG. 5, Figure A is an exploded plan view, and Figure B is a cross-sectional view of the mounting. In the figure, the same reference numerals as in FIGS. 2 to 4 indicate the same parts. Further, 21 is a GND pattern, 22 is a window, 23 is a capacitor electrode pattern, and 24 is a coil pattern.

The first layer 10-1 of the multilayer circuit board is printed with a GND pattern 21 with a window (no conductor) 22 in the center, and the second layer 10-2 is provided with a capacitor electrode. The pattern 23 and the coil pattern 24 are formed by printing. At this time, the coil pattern 24 is provided in the center, and the capacitor electrode pattern 23 is provided so as to surround the coil pattern 24.

Similarly, a coil pattern 24 and a capacitor electrode pattern 23 surrounding the coil pattern 24 are formed on the layer 10-3 by printing. When the layers formed with each pattern are laminated in this way, a resonant portion with a cross-sectional structure as shown in FIG.
The same circuit as A) is obtained.

When the resonant section is used as a high frequency filter, in this example, the capacitor electrode pattern 23 formed on the layer 10-3 is connected to the GND terminal. In this way, the GND electrode is arranged to surround the coil portion, so that it is possible to shield the magnetic field that spreads in the lateral direction of the coil.

[0101] Therefore, no magnetic influence is exerted on other circuit patterns.

Note that the configuration examples shown in FIGS. 2 to 5 can be modified as follows.

(1) In the above configuration example, an example was explained in which the capacitor of each resonant part was made of two layers and the coil was made of two patterns, but these may also be made of a single layer or one turn.
Further, it may have a structure of two or more layers and two or more turns.

(2) The high frequency filter mounted on the multilayer circuit board can be used as a single element, but it can also be built into the mounting board together with other components.

(3) As a capacitor electrode pattern,
The shape is not limited to the above example, and may be circular or the like.

(4) The input terminal and the output terminal may be connected to the coil portion, but since the resonators are coupled to each other by the coil, it is better to provide them as close to the capacitor as possible.

[0107] The operation of the above configuration example is as follows.

[0108] Among the plurality of resonant parts provided, an input terminal is connected to one of the resonant parts arranged at both ends, and an output terminal is connected to the other.

[0109] When a high frequency signal is applied to this input terminal,
Since the coil patterns of each resonant section are magnetically coupled, each resonant section resonates at a specific frequency.

[0110] Therefore, among the above-mentioned high frequency signals, only a signal of a specific frequency is outputted to the output terminal.

[0111] In this way, the high frequency filter can be constructed by simply providing a plurality of resonant sections each composed of an LC resonant circuit consisting of a capacitor C and a coil L, so that the manufacturing process is simple and easy to manufacture.

Furthermore, by arranging the resonant portions in the stacking direction, a compact high frequency filter can be obtained, there is no need to consider interstage interference, and high Q filter characteristics can be easily obtained.

Furthermore, in this case, since the capacitor section arranged in the lamination direction of the board has a structure in which a GND pattern (for example, 11 and 12 in FIG. 4) is formed on the outer layer of the multilayer circuit board, the electric field is affected by the GND pattern. Can create a shield.

[0114] Therefore, it is possible to eliminate the electric field leaking to the outside from the capacitor section, and prevent adverse effects on external circuits.

The high frequency filter of the present invention is also suitable as a high frequency demultiplexing filter.

FIG. 6 shows an example of the configuration of a duplexer as an example of a branching filter.

In FIG. 6, L1 to L3 are coils,
C1 to C3 are capacitors, Rx is the receiving section, Tx
indicates a transmitter, and ANT indicates an antenna.

[0118] This duplexer supports one antenna AN
It is used when T is shared between the transmitter Tx and the receiver Rx, and includes multiple coils L1 to L3 and multiple capacitors C.
1 to C3. And coil L1
and capacitor C1 and coil L2 and capacitor C
3 constitute parallel resonant circuits each having a different resonant frequency.

In the above circuit, a certain frequency fA is passed between the transmitter Tx and the antenna ANT while another frequency fB (fB ≠ fA) is blocked, and vice versa between the antenna ANT and the receiver Rx. , fB
passes through and blocks fA.

[0120] If the present invention is applied to such a branching filter, the coil and capacitor are formed of thick films, so the filter can be made smaller and can be used in a high frequency band.

However, in such a duplexer, the circuit between the transmitter Tx and the antenna ANT (coil L1,
capacitors C1, C2) and the circuit between antenna ANT and receiver Rx (coils L2, L3, capacitor C
3) may become a problem, and when downsizing, the distance between the coils (especially coils L1 and L2) may become a problem.
The problem is the magnetic coupling between

[0122] Therefore, it is preferable to use a branching filter having the following configuration.

(1) In a high frequency demultiplexing filter in which a plurality of circuits including at least thick film coils and capacitors are provided on a circuit board using a dielectric material to perform demultiplexing of high frequency signals, the plurality of circuits described above are By arranging the capacitor electrode patterns of the adjacent circuits between the coil patterns of the adjacent circuits to be branched, magnetic shielding is provided between the coil patterns.

(2) In the high frequency demultiplexing filter described in (1) above, each capacitor electrode pattern is arranged so as to surround each of the coil patterns.

(3) In the high frequency demultiplexing filter described in (1) above, a multilayer circuit board is used as the circuit board, and each of the capacitor electrode patterns of the adjacent circuits is separated from each other, and the separated electrode patterns are separated from each other. It is composed of two integrated electrode patterns which are arranged so as to be sandwiched from both sides via a dielectric layer of a circuit board and are electrically connected.

With the configuration as described in (1) above, two coils of adjacent circuits are magnetically shielded by the capacitor electrode pattern.

[0127] Therefore, since the magnetic coupling between both coils is reduced and interference between circuits is reduced, when this high frequency demultiplexing filter is used, its characteristics are not deteriorated.

[0128] Furthermore, when configured as in (2) above, the capacitor electrode pattern surrounds the coil, so that
The magnetic shielding effect can be further improved. Therefore, magnetic coupling between the coils becomes extremely small.

Furthermore, with the configuration as described in (3) above, it is possible to reduce not only the magnetic coupling between the coils but also the coupling due to the electric field between the capacitors. Thereby, magnetic coupling and electric field coupling can be reduced at the same time.

[0130] Hereinafter, an example of the structure of such a high frequency demultiplexing filter will be explained based on the drawings.

[0131] Fig. 7 is a mounting diagram of the high frequency demultiplexing filter, with Fig. A being an exploded plan view and Fig. B being a sectional view. In the figure, the same symbols as in FIG. 6 indicate the same parts, 101 is a circuit board (each circuit board forming the multilayer circuit board), 102 to 107 and 114 to 116 are capacitor electrode patterns, 108
113 indicates a coil pattern, and 117 indicates an interrupted region.

This configuration example is an example in which the duplexer shown in FIG. 6 above is mounted on a multilayer circuit board (three layers).

[0133] On the top layer circuit board 101 of the multilayer circuit board, capacitor electrode patterns 102 and 103, which are the antenna ANT side electrodes of capacitors C3 and C1, are arranged.
They are integrally patterned by printing to form an integrated electrode, and on both sides thereof, coil patterns 110 and 108 constituting coils L1 and L2 are patterned integrally with the capacitor electrode patterns 102 and 103 by printing.

That is, the coil pattern 110 forming the coil L1 and the coil pattern 108 forming the coil L2 are placed apart from each other on both sides of the capacitor electrode patterns 102 and 103 forming the capacitors C1 and C3. capacitor electrode patterns 102 and 103 are formed between the capacitor electrode patterns 108).

Further, on the uppermost layer of the circuit board 101, a coil pattern 112 constituting the coil L3 and a capacitor electrode pattern 114 constituting the capacitor C2 are patterned by printing, separately from the above-described pattern.

[0136] On the internal circuit board 101, a capacitor electrode pattern (separated electrode) 107 constituting the counter electrode (electrode on the transmitter Tx side) of the capacitor C1 is patterned by printing, and the capacitor electrode pattern 107 is integrated with the capacitor electrode pattern 107. Specifically, a coil pattern 111 constituting the coil L1 and a capacitor electrode pattern 115 constituting the opposing electrode of the capacitor C2 are patterned by printing.

[0137] Also, on the internal circuit board 101, a capacitor electrode pattern (separated electrode) 106, which constitutes the counter electrode (electrode on the receiving section Rx side) of the capacitor C3, is printed separately from each of the above patterns. Coil patterns 109 and 113, which constitute coils L2 and L3 integrally with this capacitor electrode pattern 106, are patterned by printing.

On the lowest layer circuit board 101, capacitor electrode patterns 104 and 105 that constitute the antenna ANT side electrodes of capacitors C3 and C1 are printed and patterned to form an integrated electrode. A capacitor electrode pattern 116, which is separated to form a capacitor C2, is patterned by printing.

The capacitor electrode pattern and coil pattern described above are formed at the same position on each circuit board 101, and predetermined connections are made using blind through holes (through holes whose interiors are filled with conductors). In this case, capacitor electrode patterns (integrated electrode patterns) 102 and 103 formed on the top layer circuit board 101 and capacitor electrode patterns (integrated electrode patterns) 104 and 105 formed on the bottom layer circuit board 101 are used. , the capacitor electrode patterns (separated electrode patterns) 106 and 107 formed on the internal circuit board 101 are formed so as to be sandwiched between the capacitor electrode patterns 102 and 103 and the capacitor electrode patterns 102 and 103 with a dielectric layer constituting the board interposed therebetween. The electrode patterns 104 and 105 are connected by a blind through hole to electrically connect (short circuit) the two electrode patterns.

[0140] Regarding the coil pattern, the uppermost layer and the internal circuit board 101 are connected using blind through holes (L1, L2, L
(connected between each coil pattern of 3), the coil has approximately 2 turns. In addition, capacitor electrode patterns 102, 1
03 and the capacitor electrode patterns 104 and 105, the relay area 117 (
3 locations) and connect with blind through holes.

As mentioned above, the coils L1 and L2 are
Since the capacitors C1 and C3 are patterned at positions separated from each other on both sides, there is almost no magnetic coupling between them, resulting in a substantially magnetic shield structure. Therefore, magnetic coupling is hardly a problem.

As for the coils L2 and L3, even if there is magnetic coupling, it is possible to design the coils L2 and L3 including coupling by setting the constants of the coils L2, L3 and the capacitor C3.

[0143] Also, capacitor electrode patterns 106, 1
07 are capacitor electrode patterns 102 and 10, respectively.
3, 104, and 105, there is almost no electric field coupling between the capacitors C1 and C3. Therefore, a duplexer is obtained in which the magnetic coupling between the coils L1 and L2 and the electric field coupling between the capacitors C1 and C3 are reduced or almost eliminated.

[0144] Fig. 8 shows another configuration example, where Fig. A shows an exploded plan view and Fig. B shows a modified example. In the figure, the same reference numerals as in FIGS. 7 and 6 indicate the same parts.

[0145] In this configuration example, the coil L1 shown in FIG.
This is an example in which the magnetic coupling between coils L1 and L2 is further reduced by changing the patterns of L2 and capacitors C1 and C3.

On the top layer circuit board 101, the capacitor electrode pattern 103 (changed in shape) surrounds the coil pattern 110 in a U-shape, and the capacitor electrode pattern 102 further surrounds the coil pattern 108 in a U-shape. On the internal circuit board 101, the coil pattern 111 is formed by the capacitor electrode pattern 107.
are enclosed in a U-shape to form a capacitor electrode pattern 106.
The coil pattern 109 is enclosed in a U-shape. Further, in accordance with the deformation of the pattern, the shapes of the capacitor electrode patterns 104 and 105 formed on the lowest layer circuit board are also changed in accordance with the upper layer electrode pattern.

As described above, by surrounding each coil pattern in a U-shape with a capacitor electrode pattern, the magnetic shielding effect is enhanced and the coils L1 and L2
This makes it possible to further reduce the magnetic coupling between the two.

Furthermore, as shown in Figure B, the coil pattern 110 can be completely surrounded by the capacitor electrode pattern 103. Note that the example in Figure B includes not only the coil pattern 110 but also the coil patterns 108 and 1.
The same applies to 09 and 111. In this case, it is possible to further enhance the magnetic shielding effect.

[0149] In addition to these, the following configurations are also possible.

(1) The circuit board is not limited to a multilayer circuit board, and a single-layer double-sided circuit board (dielectric board) may be used.

(2) It is also possible to form the coils L2 and L3 as one helical coil, and take out the center tap and connect it to the capacitor C3.

(3) In the above configuration example, the capacitor is 2
Although the layers and coils are configured with two turns, the present invention is not limited to this example, and may be arbitrarily changed. However, the interference caused by the electric field can be reduced by setting the antenna-side electrode of the capacitor on the outside.

(4) Applications include not only the duplexer of the above configuration example but also other duplexers and various high frequency demultiplexing filters.

(5) In order to increase the capacitance of the capacitor, it is also possible to configure only the substrate between the electrodes of the capacitor section using a high dielectric constant material.

The configurations shown in FIGS. 7 and 8 achieve the following effects.

(1) Magnetic coupling can be reduced between coils in each demultiplexing circuit. Therefore, even if the pattern density is increased, there is little deterioration of the characteristics, so it is possible to downsize the high frequency demultiplexing filter.

(2) When the coil pattern is arranged so as to be surrounded by the capacitor electrode pattern, the magnetic shielding effect between the coils is further improved, and interference between the coils is extremely reduced. Therefore, even when the device is downsized, there is almost no characteristic deterioration.

(3) In addition to magnetic coupling between coils,
Since the coupling due to the electric field between the capacitors can also be reduced, interference between the demultiplexing circuits is extremely reduced.

[0159] Therefore, even higher density packaging is possible and miniaturization is possible.

(4) Since interference between circuits can be reduced, miniaturization is possible without deteriorating characteristics.

[0161] Therefore, when manufacturing a high frequency demultiplexing filter, the number of filters that can be taken out from the original substrate increases, making it possible to reduce costs accordingly.

(5) If a multilayer circuit board is used as the circuit board, the necessary capacitors and coils can be easily obtained, and at the same time, the mounting area can be extremely small.

Further, a helical type coil can be obtained (large L and Q can be obtained), and the capacitor can have a large capacity, which is advantageous for miniaturization.

Next, specific examples when the high frequency circuit of the present invention is used as an interstage circuit between resonators of a dielectric filter are shown in FIGS.
This will be explained according to FIG.

In the high frequency dielectric filter shown in FIG. 11, for example, two dielectric resonators 21 and 22 are provided so as to be in contact with each other on one side.
An interstage circuit board 3 is provided on one end surface in the longitudinal direction. As shown in FIG. 13, in this interstage circuit board 3, a helical coil L and capacitors C1 to C4 are formed as a thick film pattern (thick film printed pattern) between layers 31, 32, and 33, and Figure 13
An interstage circuit is formed.

[0166] The coupling between the substrate 3 and the dielectric resonators 21 and 22 is achieved by coupling the dielectric resonators 21 and 22, for example, as shown in FIG.
, 22 and the multilayer board 3 are fixed by soldering. In this case, resonator solder pads 35, 35 connected to internal circuits are formed on the surface of the substrate 3. Note that the number of dielectric resonators connected and the arrangement of L and C can be changed in various ways.

By the way, when patterning the interstage circuit board 3 of a dielectric resonator as shown in FIG. 12, the interstage circuit board 3 becomes much smaller in shape than the dielectric resonators 21 and 22. Therefore, the solder pads 35 formed on the substrate 3 for soldering the resonators 21 and 22 to the interstage circuit board 3 become a large space factor within the area on the substrate 3.

Specifically, as shown in FIG. 13, the capacitors C1 to C4 are actively formed under the component solder pads 35 (in a direction perpendicular to the stacking direction), thereby forming the interstage circuit board 3. Aim to downsize the At this time, unnecessary routing of wiring is eliminated, so capacitors C1 to C
4. Unnecessary inductance that occurs when connecting 4 can be reduced.

When designing an interstage circuit of a dielectric resonator having a configuration having a coil L as shown in FIG. 12, the Q of the coil L influences the amplitude characteristics of the filter. That is, if the Q of L is low, the steepness of the passband characteristics will become sloppy. In order to design the coil without lowering the Q of L, it is necessary to pattern the coil in a helical shape and arrange the coil so that it is not covered by other electrode patterns.

Therefore, as shown in FIG.
5, arrange L in a helical shape so that it does not cover other electrode patterns. Specifically, it is preferable that the electrode of the capacitor C be built under the solder pad 35, and the coil L be built in the lower part of the gap between the solder pads 35. With such a configuration, the interstage circuit board 3 can be made small and a high Q L can be obtained. Furthermore, in the case of multiple stages as shown in FIG. 14, since the L pattern is arranged via the solder pad 35, the pad 35 can also reduce coupling between the L's.

[0171]

[Examples] Hereinafter, the present invention will be explained in more detail by giving specific examples of the present invention.

A low-pass filter having the circuit configuration shown in FIG. 9A was manufactured. FIG. 9B shows an exploded perspective view of the board illustrating the mounting state of this low-pass filter, and FIG. 9C shows a sectional view of the mounting of this low-pass filter. In addition, Fig. 9A
The numbers of the circuit diagram correspond to the numbers of the mounting explanatory diagram of FIG. 9B and the mounting sectional view of FIG. 9C, and FIG. 9C is a sectional view taken along the line XX' of FIG. 9B.

[0173] This low-pass filter was manufactured as follows.

[0174] 30% by volume of alumina particles and 70% by volume of strontium borosilicate glass frit are mixed, a binder and a solvent are added thereto, and the mixture is kneaded to form a slurry.
A substrate green sheet was prepared by the doctor blade method. Next, through holes were formed in the substrate green sheet, and a conductive paste containing Ag particles was printed.

[0175] The substrate green sheets printed with the conductive paste were laminated and hot pressed at 50°C and 200 kgf/cm2.

After hot pressing, the binder was removed and the product was fired in air at 900° C. for 10 minutes using a tunnel furnace to obtain a low-pass filter.

300MH of the substrate of this low-pass filter
The dielectric constant at z ~1 GHz is 7.5 to 8.5
It was within the range of

[0178] The method for measuring the dielectric constant is JIS C 2
141.

Further, the diameter of each coil was 2 mm or less, the inductance value was 10 nH or less, and the capacitance of each capacitor was 10 pF or less.

[0180] The overall dimensions of this low-pass filter were 10 x 5 x 0.7 mm.

A graph showing the bandpass characteristics of this low-pass filter is shown in FIG.

From the above examples, it is clear that according to the present invention, an 800 MHz band low-pass filter having extremely good characteristics can be obtained, and moreover, it can be extremely miniaturized.

[0183]

[Effects of the Invention] Dielectric resonant filters conventionally used for high frequencies cannot be miniaturized because their dimensions are determined depending on the wavelength, but the high frequency filter of the present invention has an LC configuration. , the dimensions do not depend on the wavelength, and miniaturization is possible.

[0184] Unlike conventional LC filters that use a substrate with a high dielectric constant to increase Q, the high frequency filter of the present invention uses a substrate with a low dielectric constant, so it can correspond to a high frequency band. Since the element constant is small in the high frequency band, the Q does not decrease even if a low dielectric constant substrate is used.

Furthermore, in the present invention, since a low-temperature firing material is used as the substrate material, a low resistance conductor material such as Ag can be used, and the resistance in the high frequency band can be reduced.

[0186] Therefore, according to the present invention, design and manufacture are easy and miniaturization is possible.
A high-performance high-frequency LC filter that can be used in a high-frequency band of Hz or higher is realized.

[0187] Furthermore, since the high frequency filter of the present invention suppresses the generation of stray capacitance near the inductor conductor,
Extremely good frequency characteristics can be obtained.

Furthermore, according to the present invention, the conventional 300MH
Low-pass filters and high-pass filters, which are difficult to design in a high frequency band of about z to 1 GHz, can be designed and manufactured relatively easily.

Furthermore, when the high frequency circuit of the present invention is used as a step circuit for a dielectric resonator, the influence of the self-resonance of the coil and the wavelength can be suppressed, and the function of the coin pattern can be effectively exhibited.

[Brief explanation of the drawing]

FIG. 1A is a circuit diagram of a high frequency bandpass filter, and FIGS. 1B and 1C are illustrations of its implementation.

FIG. 2A is a circuit diagram of a resonance section of a high frequency filter, and FIG. 2B is an explanatory diagram of its implementation.

FIG. 3A is a circuit diagram of a magnetically coupled high frequency filter, and FIG. 3B is a cross-sectional view of its implementation.

[Figure 4] Figure 4A shows a magnetically coupled high frequency filter (two sets)
4B is a sectional view of its implementation, and FIG. 4C is a partially enlarged view thereof.

5A is an exploded plan view of a modification of the high frequency filter shown in FIG. 2, and FIG. 5B is a cross-sectional view of its implementation.

[Figure 6] Figure 6 shows a high frequency demultiplexing filter (duplexer)
FIG.

FIG. 7A is an exploded plan view of a high frequency demultiplexing filter (duplexer), and FIG. 7B is a cross-sectional view of its implementation.

FIG. 8A is an exploded plan view of a high frequency demultiplexing filter (duplexer), and FIG. 8B is a modification thereof.

FIG. 9A is a circuit diagram of a low-pass filter, FIG. 9B
9C is an exploded perspective view thereof, and FIG. 9C is a sectional view thereof.

FIG. 10 is a graph showing frequency characteristics (bandpass characteristics) of the low-pass filter shown in FIG. 9;

FIG. 11 is a perspective view of an interstage circuit connected to a dielectric resonator.

FIG. 12 is a circuit diagram of FIG. 11;

FIG. 13 is an exploded perspective view of the interstage circuit of FIG. 11;

FIG. 14 is a circuit diagram showing yet another interstage circuit.

[Explanation of symbols]

10-1, 10-2, 10-3 Each layer 11 of the multilayer circuit board GND pattern 12 Capacitor electrode pattern 13 Coil pattern 14 Blind through hole L Coil C Capacitor 101 Circuit board 102-107 Capacitor electrode pattern 108-1
13 Coil patterns 114 to 116 Capacitor electrode pattern 117
Relay area ANT Antenna Tx Transmitting section Rx Receiving section L1 to L3 Coil C1 to C4 Capacitors 21, 22 Dielectric resonator 3 Interstage circuit board 31, 32, 33 Each layer of circuit board 35 Solder pad

Claims (7)

[Claims] 1. A high frequency circuit in which a resonant circuit including at least a thick film coil pattern and a thick film capacitor electrode pattern is provided on a substrate, the substrate being formed of a low temperature firing material, A high frequency circuit characterized in that the dielectric constant of the substrate near the coil pattern is 15 or less. 2. The high frequency circuit according to claim 1, wherein the dielectric constant of the substrate between the electrode patterns of the capacitor section is higher than the dielectric constant of the substrate near the coil pattern. Claim 3: Claim 1 used as a high frequency filter.
Or the high frequency circuit described in 2. 4. The high frequency circuit according to claim 1, which is used as an interstage circuit of a dielectric resonator of a high frequency filter. 5. The high frequency circuit according to claim 4, wherein the coil pattern and the capacitor electrode pattern are built into the substrate, and a plurality of pads for connecting the plurality of dielectric resonators are provided on the surface. 6. The high frequency circuit according to claim 5, wherein the coil pattern is provided inside the gap between the pads, and the capacitor electrode pattern is provided inside the pad in the thickness direction of the substrate. 7. The high frequency filter has a frequency of 100 MHz.
The high frequency circuit according to any one of claims 3 to 6, which is used in the above frequency band.