JPH046911A - High frequency filter - Google Patents

Abstract

PURPOSE:To make the filter small and to reduce the cost by mounting plural resonance parts being basic building blocks onto a multi-layer printed circuit board while they are coupled magnetically. CONSTITUTION:Plural resonance parts each comprising a capacitor electrode pattern 12 formed as a thick film to any of layers 10-1-10-3 of a multi-layer printed circuit board and a coil pattern 13 formed in a thick film connecting to the capacitor electrode pattern 12 are provided in the stack direction (longitudinal direction) of the multi-layer printed circuit board and the plural resonance parts are arranged so that the coil patterns 13 of the adjacent resonance parts are magnetically coupled. Then an input terminal is connected to one of the resonance part arranged at both ends of the plural resonance parts and an output terminal is connected to the other. When a high frequency signal is applied to the input terminal, since the coil patterns of the resonance parts are coupled magnetically, each resonance part is resonated at a specific frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high frequency filter, and more particularly to a high frequency filter that uses a multilayer circuit board to realize miniaturization and cost reduction.

[Conventional technology]

Conventionally, ceramic filters, SAW filters, helical filters, LC filter modules, and the like have been known as filter elements for high frequency band pass filters.

In the ceramic filter, the shape of the filter element (ceramic plate) is sensitive to electrical characteristics, and its frequency is adjusted by polishing the element (ceramic vibrator) and adjusting its thickness. Such frequency adjustment is time-consuming and causes high component costs.

Also, since the filter element itself actually vibrates,
Packaging that takes into consideration the vibration space of the element is required. Therefore, the component becomes large.

Since the SAW filter is made of a single crystal material, it is more complicated to manufacture than a ceramic material (sintered material). 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 a SAW filter, since the surface of the filter element actually vibrates, packaging must take into account the vibration space. For this reason, especially in the height direction,
It becomes a large part.

However, since only the surface of a SAW filter vibrates, it does not require a large package like a ceramic filter.

The above-mentioned LC filter is multi-staged to improve bandpass characteristics. However, even when using discrid components or thick film components, it is difficult to reduce the size because interference between elements must be taken into consideration.

FIG. 5 is a diagram showing an example of mounting a conventional high-frequency filter, in which figure A is a circuit diagram, figure C 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, 4.5 is a coil button, and 9 is a capacitor electrode pattern (common electrode button).

Further, C1 and C2 are capacitors, L, 1.1. ．． 2 represents a coil, and M represents mutual inductance.

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

As shown in Figure A, the circuit of the above-mentioned high frequency filter consists of a first parallel resonant circuit (LC resonant circuit) consisting of a coil L1 and a capacitor C1, and a second parallel resonant circuit (LC resonant circuit) consisting of a coil L1 and a capacitor C2. LC resonant circuit) 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 the diagram and the diagram.

On the surface (one side) of the printed circuit board l, one electrode pattern 2 of the capacitor C1 and a coil pattern 4 which becomes a part of the coil L1 are integrally formed by printing, and one electrode pattern of the capacitor C2 is formed integrally by printing. The pattern 3 and the coil pattern 5, which becomes a part of the coil L2, are integrally formed by printing.

Also, on the back side (the other side), the other electrode pattern 9 of the capacitors C1 and C2, the coil pattern 4 which becomes part of the coil L L, and the coil pattern 5 which becomes a part of the coil L2 are printed integrally. Predetermined portions of each pattern on both the front and back surfaces are connected using through holes, etc., to form a circuit configuration as shown in Figure A.

[Problem to be solved by the invention]

The above-mentioned conventional devices had the following drawbacks.

(1) Bandpass filters such as ceramic filters and SAW filters are expensive (and difficult to miniaturize).

(2) The LC filter is the ceramic filter mentioned above or the SA filter.
Although the cost is lower than that of the W filter, it is difficult to miniaturize due to problems such as interference between elements.

(3) In the case of the high frequency filter shown in FIG. 5, since the printed circuit board is a single board, the coils are arranged horizontally and magnetically coupled.

Therefore, the insertion loss becomes large in the amplitude characteristics.

(4) In the high frequency filter shown in FIG. 5, since the LC resonance circuits are arranged horizontally, the filter element becomes large.

In particular, when three or more LC resonant circuits are arranged in a row, the bandpass characteristics are improved compared to when two LC resonant circuits are arranged, but the size of the filter element is inevitably increased.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such conventional drawbacks, to make a high frequency filter smaller in size, and to realize a reduction in cost.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a capacitor electrode pattern formed of a thick film on any layer constituting a multilayer circuit board, and a coil pattern connected to the capacitor electrode button and formed of a thick film. A plurality of resonant parts are provided in the stacking direction (contraction direction) of the multilayer circuit board, and the plurality of resonant parts are arranged so that the coil patterns of adjacent resonant parts are magnetically coupled. be.

[Effect]

Since the present invention is configured as described above, it has the following effects.

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.

When a high-frequency signal is applied to this input terminal, each resonance section resonates at a specific frequency because the coil patterns of each resonance section are magnetically coupled.

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

In this way, L consisting of capacitor C and coil L
Since a high frequency filter can be constructed by simply providing a plurality of resonant sections each composed of a C resonant circuit, the manufacturing process is simple and easy to manufacture. Furthermore, since the resonant parts are arranged in the stacking direction, a compact high frequency filter can be obtained.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

1 to 3 are diagrams showing a first embodiment of the present invention, in which FIG. 1 is an explanatory diagram of mounting a resonant section, FIG. 2 is an explanatory diagram of mounting a high frequency filter, and FIG. , high frequency filter (2
An implementation example of the following is shown below.

In the figure, L is a coil, C is a capacitor, 10-1 to 10-
3 each layer of the multilayer circuit board, 11 GND pattern, 12
is the capacitor electrode pattern, 13 is the coil pattern, L
1 to Ln are coils, 01 to Cn are capacitors, IN is an input terminal, OUT is an output terminal, 14 is a blind through hole, 15 is a donut-shaped electrode, 16 is a hole, and 17 is a connection part (
18 indicates a conductor penetration portion.

In this embodiment, a parallel resonant circuit (LC resonant circuit) of a coil L and a capacitor C is used as the basic resonance part, and a multilayer circuit is constructed by magnetically coupling a plurality of these basic resonance parts to each other. This is an example in which a high frequency bandpass filter is constructed by mounting it on a substrate.

First, as shown in Figure 1A, the basic resonance part is connected to the coil L.
It consists of a parallel resonant circuit (LC resonant circuit) consisting of a capacitor and a capacitor.

becomes. When this resonant section is mounted on a multilayer circuit board, patterning is performed as shown in FIG. 1 (exploded plan view), taking into account the passband of the filter.

On the first layer 10-1 of the multilayer circuit board, a GND pattern 11 is formed by printing a conductor (a thick-film GND conductor pattern), and on the second layer 10-2, one electrode of a capacitor C is formed. The capacitor electrode pattern 12 and the coil pattern 13 forming a part of the coil L are legally printed and formed using a conductor, and the third layer 10-3 includes the following:
The other electrode of capacitor C (in this example, the GND side electrode)
The capacitor electrode pattern 12 constituting the capacitor electrode pattern 12 and the 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, but
When mounted on a multilayer circuit board, the capacitor section can be shielded from electric fields.

The circuit of the high frequency filter (band pass filter) in which a plurality of resonant parts (LC resonant circuits) shown in FIG. 1 are provided and magnetically coupled to each other is as shown in Part 2A.

The resonant parts each consist of a parallel resonant circuit (LC resonant circuit) of coil Lt and capacitor C1, coil L2 and capacitor C2, coil I, 3 and capacitor C3'-'-coil Ln and capacitor Cn, respectively. Coils of adjacent unit circuits are magnetically coupled.

When the circuit in Figure 2A above is mounted on a multilayer circuit board, the second
It will look like the figure (cross-sectional view of mounting).

First layer 10-1, second layer 10-2, and third layer 1
0-3 are each printed with the pattern shown in the opening of FIG. 1 (forming a thick film pattern), and these are laminated to form a resonant section.

n such resonant parts are formed in the fourth layer 1 (L-4 and below), and the coil patterns 13 in each unit circuit are laminated so that adjacent coils are magnetically coupled. do.

Due to this lamination, each resonant part is arranged in the lamination direction (contraction direction) of the multilayer circuit board.

FIG. 3 shows a mounting example (two sets) of a high frequency filter using two of the above-mentioned resonant parts.

In Figure 3, A is the circuit diagram, the opening is the mounting cross section, and C is a partially enlarged view (
This is part a of the diagram.

This high frequency filter (band pass filter) has two unit circuits (I, ICI resonant circuit and L2
C2 resonant circuit) and is built into a six-layer multilayer circuit board.

As shown in the figure, each layer constituting the multilayer circuit board has a second
Each pattern is formed by printing in the same manner as shown in the figure, and the coils of the two resonant parts are magnetically coupled.

More specifically, it is as follows. Top layer 10-
A GND terminal (GND) and an input terminal (IN) are formed on the layer 10-1, a GND pattern 11 is formed on the layer 10-1, and a GND pattern 11 is formed on the layer 10-1.
The capacitor electrode pattern 12 and the coil pattern 13 are integrally formed on the layer 0-2, and the capacitor electrode pattern 12 and the coil pattern 13 are integrally formed on the layer 10-3.

Then, the capacitor electrode pattern 12 formed on the layer 10-3 and the GND pattern 11 formed on the layer 10-1 were formed on the layer 101 using a blind through hole (a through hole whose inside is filled with a conductor) 14. Connect to GND terminal.

In addition, the coil batten 13 formed on the layer 10-2 and 10-3
A blind through hole 14 connects between the two.

Further, a capacitor electrode pattern 12 and a coil pattern are formed on the layers 10-4 and 10-5, and a GND
Forms an output terminal (OUT) with a terminal (GND). 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 105 is connected through the blind through hole. 14 to connect to the GND terminal.

In this way, each pattern formed on layers 10-1 to 10-3 constitutes one resonant section, and each pattern formed on layers 104 and 10-5 constitutes one resonant 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.

In addition, the connection with the input terminal IN and output terminal OUT is as follows.
Do it as follows. The input terminal IN is connected to the capacitor electrode pattern 12 formed on the layer 10-2, and the output terminal 0LIT is connected to the capacitor electrode pattern 12 formed on the layer 10-4.

At that time, the GND pattern 11 formed on the layer 10-1,
It penetrates the capacitor electrode button 12 formed on the layer 10-5 and is connected using a blind through hole, but this is done using a donut-shaped electrode as shown in FIG.

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

FIG. 4 is an explanatory diagram of the implementation of the second embodiment, in which Figure A is an exploded plan view and Figure 0 is a sectional view of the implementation. In the figure, Figures 1 to 3
The same reference numerals as in the figure indicate the same parts. In addition, 21 is a GND pattern, 22 is a window, 23 is a capacitor electrode pattern, 2
4 indicates a coil pattern.

This embodiment is a modification of the resonant section shown in FIG. 1, and enables electric field shielding of the capacitor section and magnetic shielding of the coil section.

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

Similarly, on the layer 10-3, a coil pattern 24 and a capacitor electrode pattern 23 surrounding the coil pattern 24 are formed by printing. By stacking the layers forming each pattern in this way,
A resonant section (the same circuit as in FIG. 1A) having a cross-sectional structure as shown in FIG. 4 is obtained.

When the above resonant section is used as a high frequency filter, in this example, the capacitor electrode pattern 2 formed on the layer 10-3 is
3 is used by connecting it 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.

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

Although the embodiments have been described above, the present invention can also be implemented as follows.

(1) In the above embodiment, 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 be made of a single layer, one turn, or two or more layers, two It may be configured with more than one tan.

(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) Ceramics and other arbitrary materials can be used as the material for the multilayer circuit board, and in this case, if a high dielectric constant material, ferrite, etc. are used, the resonator can be made smaller.

Therefore, the module is also small.

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

(5) 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.

〔Effect of the invention〕

As explained above, the present invention has the following effects.

(1) Compared to ceramic filters, SAW filters, etc., it has a simpler structure and is easier to manufacture, so it is cheaper.

(2) Since they can be arranged and built in the stacking direction of a multilayer circuit board, the mounting area can be reduced and miniaturization can be achieved.

(3) In the LC filter module, it is necessary to consider interstage interference, but in the filter of the present invention, there is no need to consider such points.

Therefore, it is easier to manufacture than an LC filter module, and can be made smaller and lower in cost.

Further, filter characteristics with high Q can be easily obtained.

(4) If a high dielectric constant material or ferrite is used as the substrate material, further miniaturization becomes possible.

(5) As shown in the above embodiment, the capacitor section arranged in the lamination direction of the board is connected to the GN on the outer layer of the multilayer circuit board.
Because of the structure in which a D pattern (for example, 11.12 in FIG. 3) is formed, an electric field shield can be created by the GND button.

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

[Brief explanation of drawings]

1 to 3 are diagrams showing a first embodiment of the present invention. FIG. 1 is an explanatory diagram of the implementation of the resonant section, FIG. 2 is an explanatory diagram of the implementation of the high frequency filter, and FIG. This is an example of mounting a high frequency filter (two sets). FIG. 4 is an explanatory diagram of implementation of the second embodiment, and FIG. 5 is a diagram showing an example of implementation of a conventional high frequency filter. 10-1, 10-2. 10-3 - Each layer of multilayer circuit board GND pattern capacitor electrode butterfly coil pattern blind through-coil capacitor Meiji Figure 2 Figure 2 Roasted theory of seven pods gA Figure Figure 4

Claims (1)

[Claims] A capacitor electrode pattern (12) formed of a thick film on any layer constituting the multilayer circuit board, and a coil pattern (13) connected to the capacitor electrode pattern (12) formed of a thick film. ) are provided in the stacking direction (vertical direction) of the multilayer circuit board, and the plurality of resonance parts are arranged so that the coil patterns of adjacent resonance parts are magnetically coupled to each other. A high frequency filter characterized in that it is arranged with