JPH04284703A - Dielectric filter comprising multi-layer board - Google Patents

Abstract

PURPOSE:To make the dielectric filter comprising a multi-layer board small in size and thin in the profile with respect to the dielectric filter comprising the multi-layer board, to facilitate the manufacture and to make a high frequency circuit employing the filter small. CONSTITUTION:On a dielectric layer 14 of a multi-layer board, IOTA/4 resonators st1, st2 are formed by a thick film conductor pattern to form the dielectric filter comprising the multi-layer board. Simultaneously, an input side impedance conversion section comprising a coil L1 and a capacitor C1 (C1=C1+C2) and an output side impedance conversion section are made of a thick film conductor pattern. Thus, the filter section and the input and the output impedance conversion sections are formed to the multi-layer board in this way to attain the input output impedance in matching with a line impedance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter using a multilayer substrate, and more particularly, to a dielectric filter using a multilayer substrate used as a high frequency filter in various communication devices.

0002

2. Description of the Related Art FIG. 6 is a diagram showing an example of a conventional high-frequency circuit. In the figure, 1 is a filter, 2 is an input-side impedance conversion circuit, 3 is an output-side impedance conversion circuit, 4,
5 indicates a circuit.

Conventionally, various types of filters have been used as high frequency filters, and among them, for example, a dielectric filter using a multilayer substrate has been known. In the case of a dielectric filter, since the resonator that constitutes the filter is large, the entire filter becomes large. In order to make this resonator smaller and thinner, the use of multilayer substrates has been considered.

This dielectric filter using a multilayer substrate is a filter in which a λ/4 type resonator is built into the multilayer substrate, and has a structure that is advantageous for miniaturization of the filter.

By the way, when constructing a dielectric filter using the above-mentioned multilayer substrate, it is not easy to set the distance between the resonant conductor of the resonator and the GND electrodes sandwiching the resonant conductor on both sides to a predetermined distance, or For miniaturization, a high dielectric constant material is used for the dielectric layer of the multilayer substrate, but this further reduces the input/output impedance.

Normally, when designing a high frequency circuit, the line impedance is set to an appropriate value (for example, 50Ω).
). However, as the filter is made smaller as described above, the input/output impedance becomes smaller than 50Ω.

Therefore, when designing a high frequency circuit using a dielectric filter made of a multilayer substrate, it is necessary to configure it as shown in FIG.

In this circuit, an input impedance conversion circuit 2 is provided on the input side of the filter 1 (a dielectric filter made of a multilayer substrate), and an output impedance conversion circuit 3 is provided on the output side, thereby changing the impedance between the circuits. Perform a matching design and match the line impedance to 50Ω.

[0009]

[Problems to be Solved by the Invention] The conventional devices as described above have the following problems. (1) As shown in Figure 6, on the input and output sides of the filter,
In the case of a matching design in which each impedance conversion circuit is provided, even if the filter is made smaller, the high frequency circuit as a whole cannot be made much smaller (it becomes larger due to the impedance conversion circuit).

(2) A dielectric filter using a multilayer substrate,
In order to design the input/output impedance to match the line impedance, it is necessary to thicken the dielectric layer between GND and the resonant conductor.

[0011] However, in order to increase the thickness, it is necessary to increase the number of times the green sheets are laminated, which is also difficult to manufacture. Furthermore, increasing the thickness also makes it difficult to downsize the filter, especially the resonator.

(3) In order to miniaturize a dielectric filter using a multilayer substrate, if the number of stacking of green sheets is reduced, the dielectric layer becomes thinner and the input/output impedance decreases.

[0013] Therefore, it is difficult to make a small filter without lowering the input/output impedance.

(4) As shown in FIG. 6, in a design in which an impedance conversion circuit is provided on the input/output side of the filter, the number of steps required to mount the high frequency circuit on the board increases and the work becomes troublesome.

The present invention solves these conventional problems, reduces the size of a dielectric filter using a multilayer substrate, facilitates manufacturing, and also reduces the size of the entire high frequency circuit using the filter. The aim is to make it achievable.

[0016]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a dielectric filter using a multilayer substrate in which a resonator is built into the multilayer substrate. In addition, these impedance converting sections were integrated by providing them on a multilayer substrate.

[0017]

[Operation] The operation of the present invention based on the above configuration will be explained.

As dielectric filters using multilayer substrates (filters with resonators built into multilayer substrates) are miniaturized,
The input/output impedance of the dielectric filter (filter section) decreases.

This impedance reduction is converted into impedance by an impedance conversion section added to the input/output section of the dielectric filter (filter section).

Therefore, in the dielectric filter using the multilayer substrate of the present invention in which the impedance conversion section is integrated, the input and output impedances can always be matched to the line impedance (usually 50Ω).

[0021] In this way, even if there is a drop in input/output impedance that occurs when a dielectric filter using a multilayer substrate is miniaturized, it can be adjusted by the internal impedance conversion section, so that the dielectric filter can be sufficiently miniaturized. can be done.

[0022] Furthermore, if the filter can be made smaller, and in particular the resonator can be made thinner, it will be possible to reduce the number of times green sheets are laminated during manufacturing, which will also facilitate manufacturing.

Furthermore, since there is no need to provide an impedance conversion circuit outside the filter as in the conventional case,
The entire high frequency circuit using the dielectric filter of the present invention is miniaturized.

[0024]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

(Description of the first embodiment) FIGS. 1 to 3 are diagrams showing the first embodiment of the present invention. FIG. 1 is an exploded perspective view of a dielectric filter using a multilayer substrate, and FIG. , X- in Figure 1
FIG. 3, a cross-sectional view taken along the Y line, is a diagram showing a dielectric filter circuit using the multilayer substrate shown in FIG.

In the figure, C1, C2, C3, C11,
C12, C21, C22 are capacitors, L1, L2
is a coil, st1 and st2 are λ/4 type resonators, IN
indicates an input terminal, OUT indicates an output terminal, and GND indicates a GND electrode.

Further, 10 is a dielectric filter made of a multilayer substrate, 11 is an input side impedance conversion section, 12 is an output side impedance conversion section, 13 is a first dielectric layer, 14 is a second dielectric layer, and 15 is a In the third dielectric layer, 16 to 18 are capacitor electrodes, and 19 is a line (explanatory line) indicating connection by a blind through hole (through hole filled with a conductor).

In the first embodiment, a dielectric filter circuit 10 using a multilayer substrate was constructed as shown in FIG. Figure 3
, the λ/4 type resonators st1, st2 and the capacitor C3 constitute a filter section (two-stage configuration), and the input side impedance conversion section 11 is connected to the input side of this filter section, and the output side impedance conversion section 11 is connected to the output side of the filter section. The conversion section 12 is connected to constitute a dielectric filter circuit 10 as a whole.

The input side impedance conversion unit 11 has a configuration in which a capacitor C1 with one end grounded and a coil L1 are connected to the input terminal IN, and the output side impedance conversion unit 12 has a capacitor C2 with one end grounded.
and the coil L2 are connected to the output terminal OUT.

Normally, with a filter configured as shown in FIG. 3, it is difficult to deal with high frequency components (especially odd-order high frequencies), and by grounding the input and output sides with capacitors, it is possible to reduce the high frequency components beyond the pass band. Band attenuation can be improved. Therefore, it has an ideal circuit configuration in the above-mentioned respects.

The input-side impedance conversion circuit 11 and the output-side impedance conversion circuit 12 described above are circuits that match the lowered input and output impedances by constructing dielectric filters using multilayer substrates.

Therefore, the line impedance (usually 5
It is necessary to determine the element constants etc. so that matching can be achieved with 0Ω). Note that the impedance is adjusted to the frequency of the passband.

Below, the circuit of FIG. 3 is mounted on a multilayer board.
An example of a dielectric filter using a multilayer substrate will be explained based on FIGS. 1 and 2.

In this example, the multilayer substrate is composed of three layers: a first dielectric layer 13, a second dielectric layer 14, and a third dielectric layer 15.

A GND electrode G is provided on the first dielectric layer 13.
ND, input terminal IN, output terminal OUT, coil L1,
Each coil L2 is formed with a thick film conductor pattern (a pattern formed by printing a thick film conductor).

[0036] Also, on the second dielectric layer 14, there are two λ
The /4 type resonators st1, st2 and the GND electrode GND are integrally formed with a thick film conductor pattern, and the capacitor electrodes 16, 17 are formed with a thick film conductor pattern.

Further, on the third dielectric layer 15, a GND
The electrode GND and the capacitor electrode 18 are formed with a thick film conductor pattern.

[0038] Then, between one end of the coil L1 and one end of the λ/4 type resonator st1, the input terminal IN and the capacitor electrode 1
6, between one end of the coil L2 and one end of the λ/4 type resonator st2, between the output terminal OUT and the capacitor electrode 17, and between one end of the λ/4 type resonator st1 and the capacitor electrode 18.
These are connected by blind through holes (through holes whose insides are filled with a conductor) (see line 19 indicating the connection).

In this way, the capacitor C11 is formed between the GND electrode GND on the first dielectric layer 13 and the capacitor electrode pattern 16, and the capacitor C11 is formed between the GND electrode GND on the first dielectric layer 13 and the GND electrode on the third dielectric layer 15. Since a capacitor C12 is formed between the capacitor C12 and GND, the combination of these two capacitors C11 and C12 is the
(C1=C11+C12) is used.

Further, a capacitor C2 is connected between the GND electrode GND on the first dielectric layer 13 and the capacitor electrode 17.
1 is formed, and a capacitor C22 is formed between the capacitor electrode 17 and the GND electrode GND on the third dielectric layer 15, so these two capacitors C21 and C22
The composite of the capacitor C2 (C2 = C21
+C22).

[0041] When manufacturing the dielectric filter having the above structure, the filter section constituting the dielectric filter and the impedance conversion circuit for matching input and output impedances are placed on the same dielectric layer of a multilayer substrate. At the same time, it is fabricated as a thick film conductor pattern.

In this case, the element constants of the impedance conversion section on the input/output side are also adjusted to predetermined values.

(Description of Second Embodiment) FIG. 4 is a diagram showing a circuit of a dielectric filter using a multilayer substrate according to a second embodiment, and the same reference numerals as in FIG. 3 indicate the same parts. Also, L21,L
22 is a coil, and C21 and C22 are capacitors.

In the second embodiment, a dielectric filter circuit 10 using a multilayer substrate was constructed as shown in FIG. Figure 4
In this case, the input side impedance conversion section 11 connects the coil L21 whose one end is grounded and the capacitor C21 to the input terminal I.
The output side impedance conversion section 12 has a configuration in which a coil L22 whose one end is grounded and a capacitor C22 are connected to the output terminal OUT.

[0045] Furthermore, the λ/4 type resonators st1, st2
, and a capacitor C3 (two-stage configuration) has the same configuration as in FIG.

Similar to the first embodiment, this dielectric filter circuit is also mounted on a multilayer substrate to form a dielectric filter.

(Description of Third Embodiment) FIG. 5 is a diagram showing a dielectric filter circuit using a multilayer substrate according to a third embodiment, and the same reference numerals as in FIG. 3 indicate the same parts. Also T1, T2
indicates a transformer.

In the third embodiment, a dielectric filter circuit using a multilayer substrate was constructed as shown in FIG. In FIG. 5, the input side impedance conversion section 11 includes a transformer T1.
This is an example in which a transformer T2 is used in the output side impedance conversion section 12, and the other configurations are the same as in FIG.

In this example, impedance matching is performed by adjusting the turns ratio of each transformer T1, T2. Further, the dielectric filter circuit is also mounted on the multilayer substrate in the same manner as in the first embodiment.

(Other Embodiments) Although the embodiments have been described above, the present invention can also be practiced as follows.

(1) The number of dielectric layers constituting the multilayer substrate may be three as in the above embodiment, but any other number may be used.

(2) The λ/4 type resonator is not limited to a two-stage configuration, but may have an arbitrary number of stages.

(3) The circuit elements constituting the impedance conversion section on the input/output side may be formed with a thick film pattern and built into the multilayer board, or some of the elements may be formed on the outer surface of the multilayer board. may be formed.

(4) The impedance conversion section is not limited to the circuit of the above embodiment, but other circuits may be used.

[0055]

[Effects of the Invention] As explained above, the present invention has the following effects.

(1) Since the impedance conversion section for performing impedance matching on the input side and output side is integrated into the dielectric filter made of a multilayer substrate, the impedance of the filter section can be reduced by making the filter smaller. Even if the impedance becomes low, it can always be matched to the line impedance.

(2) When the dielectric filter using the multilayer substrate of the present invention is used in a high frequency circuit, there is no need to provide an impedance conversion circuit as a separate circuit as in the conventional example shown in FIG. Therefore, the entire high frequency circuit can be miniaturized.

(3) When mounting a filter circuit on a multilayer substrate, the filter section and the impedance conversion section on the input/output side can be simultaneously formed as a thick film conductor pattern, making it easy to manufacture the filter.

(4) When forming the filter part on a multilayer substrate, even if the impedance decreases by reducing the number of times the green sheets are laminated, it can be compensated for by the impedance conversion circuit, making the filter even more compact. It becomes possible to make it thinner.

Moreover, if the number of times the green sheets are stacked is reduced, the number of manufacturing steps will be reduced accordingly, and the work will be easier.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view of a dielectric filter using a multilayer substrate according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the X-Y line in FIG. 1;

FIG. 3 is a diagram showing a dielectric filter circuit using a multilayer substrate according to the first embodiment.

FIG. 4 is a diagram showing a dielectric filter circuit using a multilayer substrate according to a second embodiment.

FIG. 5 is a diagram showing a dielectric filter circuit using a multilayer substrate according to a third embodiment.

FIG. 6 is an example of a conventional high frequency circuit.

[Explanation of symbols]

13 First dielectric layer 14 Second dielectric layer 15 Third dielectric layer 16 to 18 Capacitor electrode 19 Blind through hole st1, st2 λ/4 type resonator GND GN
D electrode C11, C12, C21, C22, C3 Capacitor L1, L2 Coil

Claims (1)

[Claims] Claim 1: Resonators (st1, st2
), impedance converters (11, 12) are added to the input parts of the dielectric filter, and these impedance converters (11, 12) are connected to the multilayer substrate. A dielectric filter using a multilayer substrate, characterized in that it is integrated with a substrate.