JPH0846403A - Substrate for dielectric filter and dielectric filter - Google Patents

Abstract

PURPOSE:To provide an inexpensive substrate for a dielectric filter for which insertion loss is small and an attenuation is large by superimposing a second printed board for connecting electric elements on a first printed board for grounding a resonator. CONSTITUTION:The first printed board 51 where input/output terminals 52, terminals 13 for grounding and a conductor pattern 14 for grounding the resonator are formed, and the second printed board 53 where the input/output terminals 54, a conductor pattern 55 for connecting the electric elements such as a coil and a capacitor, etc., and the conductor pattern 56 for grounding are formed are mutually superimposed, and the input/output terminals 52 of the first printed board 51 and the input terminals 54 of the second printed board 53 are mutually connected. By using a material for which the dielectric constant of the second printed board 53 is smaller than the dielectric constant of the first printed board 51, unrequired capacitance by the substrate between circuit patterns is reduced and the attenuation amount is made large.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a dielectric filter, and in particular, a dielectric of a high frequency band of several 100 (MHz) to several (GHz) such as a microwave band used for mobile band communication equipment. The present invention relates to a substrate having a structure suitable for a filter.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional dielectric filter substrate, (a) is a perspective view, (b) is an enlarged view of portion B in (a), and FIG. 7 is the dielectric shown in FIG. A body filter substrate is shown, (a) is a plan view and (b) is a bottom view.

A conventional dielectric filter substrate is composed of a single substrate, and a printed circuit board 11 is generally used as this substrate. An input / output terminal 12, a grounding terminal 13, a conductor pattern 14 for grounding a resonator, and a conductor pattern 15 for connecting electric elements such as a capacitor and an inductor are formed on the component surface of the printed circuit board 11. On the solder side of the substrate 11, the input / output terminals 1
2, a grounding terminal 13, and a conductor pattern 14 for grounding the resonator are formed. These input / output terminal 12, grounding terminal 13, conductor pattern 14, and conductor pattern 1
5 is formed by cutting off a part of copper foil adhered to the front and back of the substrate body by means of etching or the like. The above-mentioned input / output terminal 12 includes the terminal pattern 12a existing on the component surface of the printed board 11 and the printed board 11
Of the terminal pattern 12b existing on the solder surface of and the half through hole 12c.
The terminal patterns 12a and 12b are short-circuited with each other. Similarly, in the grounding terminal 13, the terminal pattern 13a on the component surface and the terminal pattern 13b on the solder surface are short-circuited to each other at the through hole 13c. The grounding conductor pattern 14a on the component side of the printed board 11 and the grounding conductor pattern 14b on the solder side of the printed board 11 are short-circuited to each other by a through hole 16.

FIG. 8 shows the appearance of a conventional dielectric filter using a printed circuit board. Here, the structure of the bandpass filter when two dielectric resonators 21 are used is shown.

The outer conductor 23 of the dielectric resonator 21 is electrically connected to the grounding conductor pattern 14. Further, the inner conductor 22 of the dielectric resonator 21 and the capacitor 24
The electric elements of the coil 25 and the coil 25 are connected to the conductor pattern 15, respectively.

FIG. 9 shows frequency characteristics of the bandpass filter shown in FIG. The center frequency of this filter is 1
At 490 MHz, the bandwidth is 23 MHz, the insertion loss is 2.3 dB, and the attenuation amount at 3800 MHz is 13 dB.

As a concrete value of each member constituting the filter, the outer dimension of the printed board 11 is 11 mm ×
The size is 11 mm × 0.3 mm, the material is FR-4 (glass epoxy), the dielectric constant of the substrate is 5.0, and the Q value of the substrate is 70. The dielectric resonator 21 has a size of □ 3 mm and a dielectric constant of 90.

[0008]

As characteristics of the dielectric filter, smaller insertion loss and larger attenuation amount are required. As shown in FIG. 10A, when the coil 25 is connected between the conductor patterns 15a and 15b for connecting electric elements, in the conventional dielectric filter substrate 11, the space between the conductor patterns 15a and 15b is increased in the conventional dielectric filter substrate 11. Equivalently as shown in FIG. 10B due to unnecessary capacitive coupling due to the substrate capacitance.
The circuit configuration is as shown in. As the frequency of the coil increases, the impedance increases and the amount of attenuation increases. However, as shown in FIG. 10B, when the parallel capacitance 41 is present, the impedance in the high frequency region decreases, so the amount of attenuation decreases. To do.

Further, as shown in FIG. 11 (a), between the conductor pattern 15c and the conductor pattern 15d, the conductor pattern 1
When capacitors 24 are respectively connected between 5d and the conductor pattern 15e and between the conductor pattern 15e and the conductor pattern 15f, unnecessary capacitance coupling occurs due to the capacitance of the substrate between the respective patterns, and therefore equivalently, FIG. In the circuit configuration shown in b), the parallel capacitors 42 and 43 reduce the amount of attenuation in the high frequency range.

Further, there is a problem that the insertion loss of the filter is deteriorated when the Q value of the substrate is low even though the Q value of the electric element such as the resonator, the coil and the capacitor is high.

In order to suppress the above-mentioned decrease in attenuation, it is necessary to increase the thickness of the substrate or use a substrate having a small dielectric constant to reduce unnecessary capacitive coupling between the patterns. However, in the former case,
There is a problem in that the thickness dimension of the filter is increased due to the increase in the thickness of the substrate. Further, in the latter case, there is a problem in that the cost of the low dielectric constant material is generally several times higher than that of the ordinary material.

Further, when a printed circuit board having a high Q value is used to improve the insertion loss, the cost of the board having a high Q value is generally several times higher than that of an ordinary one.

Therefore, an object of the present invention is to provide an inexpensive dielectric filter substrate capable of reducing the insertion loss of the dielectric filter and increasing the attenuation amount of the dielectric filter. is there.

[0014]

According to the present invention, a first printed board having an input / output terminal, a grounding terminal, and a conductor pattern for grounding a dielectric resonator, and an input / output terminal. , And a second printed circuit board having a conductor pattern for connecting electric elements are overlapped with each other, and the input / output terminal of the first printed circuit board and the second printed circuit board are connected to each other.
A dielectric filter substrate, characterized in that the input / output terminals of the printed circuit board are electrically connected to each other.

According to a second aspect of the present invention, the dielectric filter substrate according to the first aspect is characterized in that the dielectric constant of the second printed circuit board is smaller than the dielectric constant of the first printed circuit board. Is obtained.

According to the third aspect of the present invention, the thickness dimension of the second printed circuit board is larger than the thickness dimension of the first printed circuit board. A body filter substrate is obtained.

According to a fourth aspect of the present invention, the dielectric loss tangent of the second printed circuit board is smaller than the dielectric loss tangent of the first printed circuit board. A body filter substrate is obtained.

According to a fifth aspect of the present invention, there is provided a dielectric filter substrate according to any one of the first to fourth aspects, and a dielectric resonator mounted on the dielectric filter substrate. A dielectric filter characterized by the following is obtained.

[0019]

1 shows a dielectric filter substrate according to a first embodiment of the present invention, FIG. 1A is an exploded perspective view, FIG. 1B is a plan view of a second printed circuit board, and FIG. 3 is a perspective view of the dielectric filter substrate shown in FIG.

With reference to FIGS. 1 and 2, the dielectric filter substrate 50 of the present embodiment comprises a first printed substrate 51 and a second printed substrate 53. On the first printed circuit board 51, a part of the copper foil adhered to the component surface and the solder surface is cut off by means of etching or the like, so that the input / output terminal 52, the grounding terminal 13 and the resonator ground. A conductor pattern 14 for forming is formed. The input / output terminal 52 is
It is composed of terminal patterns 52a and 52b formed on the component surface and the solder surface of the substrate 51 and half through holes 52c, and the terminal patterns 52a and 52b are short-circuited to each other by the half through holes 52c. Similarly, the grounding terminal 13 includes terminal patterns 13a and 13b formed on the component surface and the solder surface of the substrate 51 and a half through hole 13c, and the terminal patterns 13a and 13b are short-circuited to each other by the half through hole 13c. Has been done. Further, in the conductor pattern 14 for grounding the resonator, the grounding conductor patterns 14, 14 on the component surface and the solder surface of the substrate 51 are short-circuited to each other by the through hole 16. As is clear from the above description, the first printed circuit board 51 has the same structure as the conventional dielectric filter substrate 11 except that the electric element connection pattern 15 does not exist.

As is apparent from FIGS. 1 (a) and 1 (b),
Electrical elements such as input / output terminals 54, coils and capacitors are connected to the second printed circuit board 53 by removing a part of the copper foil on the component surface and the solder surface by means of etching or the like. A conductor pattern 55 for performing the wiring and a grounding conductor pattern 56 are formed.

The first printed circuit board 51 and the second printed circuit board 53 are overlapped with each other to form the grounding conductor pattern 14 of the first printed circuit board 51 and the grounding conductor pattern 56 of the second printed circuit board 53. Are electrically joined. Further, the input / output terminal 52 of the first printed board 51 and the input terminal 54 of the second printed board 53 are connected to each other.

The dielectric constant of the second printed circuit board 53 is set to the first
By using a material having a dielectric constant smaller than that of the printed circuit board 51, unnecessary capacitance due to the circuit board between the circuit patterns can be reduced and the amount of attenuation can be increased.

A printed circuit board having a low dielectric constant is expensive, but as in the case of the present embodiment, only a printed circuit board portion (second printed circuit board 53) for electrical element connection that directly affects the filter characteristics is low. By using a dielectric material, the cost can be kept lower. As the first printed board 51, an ordinary inexpensive board may be used.

FIG. 3 is a perspective view of a dielectric filter using a dielectric filter substrate according to a second embodiment of the present invention. The dielectric filter substrate of the present embodiment has substantially the same configuration as the dielectric filter substrate of the first embodiment, and the same parts as those of the first embodiment are designated by the same reference numerals and the description thereof is omitted. To do.

A second printed circuit board 53 is mounted on the first printed circuit board 51, and these are connected to the input / output terminals 5
2 and the input / output terminal 54, and these are connected by the ground plane 14 and the ground plane 56. The dielectric resonator 21 is connected to the grounding conductor pattern 14 on the first printed board 51. The internal conductor 22, the capacitor 24, and the coil 25 of the dielectric resonator 21 are connected to the conductor pattern 55 of the second printed board 53.

The outer shape of the first printed circuit board 51 is 1
1 mm × 11 mm × 0.3 mm, the dielectric constant of the substrate 51 is 5.0 (material: FR-4), and the Q value of the substrate 51 is 70. The outer shape of the second printed circuit board 53 is 9 m.
m × 4 mm × 0.5 mm, the dielectric constant of the substrate 53 is 3.7
(Material: BT substrate), the Q value of the substrate 53 is 500.
The board for connecting the electric elements, that is, the second printed board 53 is a board having a large board thickness, a low dielectric constant, and a high Q value as compared with a board for a conventional dielectric filter. The dielectric resonator and other element values are the same as those described in the prior art.

As described above, by making the thickness dimension of the second printed circuit board 53 larger than the thickness dimension of the first printed circuit board 511, unnecessary capacitance due to the circuit pattern between the circuit patterns is reduced and the attenuation amount is reduced. Can be large. Therefore, without increasing the height of the dielectric filter,
Since it is possible to increase only the substrate thickness of a portion deeply related to the substrate capacitance, it is possible to reduce the height dimension as compared with the conventional case.

Further, as described above, the Q value of the second printed circuit board 53 is made larger than the Q value of the first printed circuit board 51 to increase the Q value between the circuit patterns, and thereby the filter The insertion loss can be made smaller, and as a result,
The amount of attenuation can be increased. A board having a high Q value is expensive, but the cost is suppressed by using a board having a high Q value only for connecting the electric elements, that is, the second printed board 53. By the way, dielectric constant x dielectric loss tangent =
Dielectric loss = 1 / Q.

FIG. 4 is a graph showing frequency characteristics of the dielectric filter shown in FIG. According to this, the insertion loss is 2.0 dB and the attenuation amount at 3800 MHz is 23 dB. In the case of the conventional dielectric filter using the printed circuit board, the insertion loss was 2.3 dB and the attenuation was 13 dB, while the dielectric filter substrate of the second embodiment was used. Loss 0.3dB, Attenuation 1
An improvement of 0 dB was seen.

FIG. 5 is a bottom view of the second printed circuit board of the dielectric filter substrate according to the third embodiment of the present invention.

In the first embodiment, as shown in FIG. 1B, the grounding conductor pattern 56 is formed on the back surface of the second printed circuit board 53, but it is not always necessary to provide it. As in the embodiment, only the input / output terminal 54 may be provided on the back surface of the second printed board 53. in this case,
The first printed circuit board and the second printed circuit board are connected to each other through the input / output terminals provided on each.

[0033]

As described above, according to the present invention, the height of the filter is improved by superimposing the second printed circuit board for electrical element connection on the first printed circuit board for resonator grounding. The thickness of the substrate for connecting electric elements can be increased without changing the thickness, and a substrate having a low dielectric constant or a high Q value can be obtained at low cost, resulting in a small insertion loss and a large attenuation amount. A filter can be realized.

[Brief description of drawings]

FIG. 1 shows a dielectric filter substrate according to a first embodiment of the present invention, in which (a) is an exploded perspective view and (b) is a second.
3 is a plan view of the printed circuit board of FIG.

2 is a perspective view of the dielectric filter substrate shown in FIG. 1. FIG.

FIG. 3 is a perspective view of a dielectric filter using a dielectric filter substrate according to a second embodiment of the present invention.

FIG. 4 is a graph showing frequency characteristics of the dielectric filter shown in FIG.

FIG. 5 is a bottom view of the second printed circuit board of the dielectric filter substrate according to the third embodiment of the present invention.

6A and 6B show an example of a conventional dielectric filter substrate, FIG. 6A is a perspective view, and FIG. 6B is an enlarged view of a portion B in FIG. 6A.

7 shows the dielectric filter substrate shown in FIG. 6, (a) being a plan view and (b) being a bottom view.

FIG. 8 is a perspective view of a dielectric filter using the dielectric filter substrate shown in FIG.

9 is a graph showing frequency characteristics of the dielectric filter shown in FIG.

10 shows a coil portion of the dielectric filter shown in FIG. 8, (a) is an enlarged view, and (b) is an equivalent circuit diagram of (a).

11 shows a capacitor portion of the dielectric filter shown in FIG. 8, (a) is an enlarged view, and (b) is an equivalent circuit diagram of (a).

[Explanation of symbols]

 13 Grounding Terminal 14 Conductor Pattern 21 Dielectric Resonator 22 Inner Conductor 23 External Conductor 24 Capacitor 25 Coil 50 Dielectric Filter Substrate 51 First Printed Circuit Board 52 Input / Output Terminal 53 Second Printed Circuit Board 54 Input / Output Terminal 55 Conductor Pattern 56 conductor pattern

Claims (5)

[Claims] 1. A first printed circuit board having an input / output terminal, a grounding terminal, and a conductor pattern for grounding a dielectric resonator, and a second printed board having an input / output terminal and a conductor pattern for connecting an electric element. And a printed circuit board of the second printed circuit board are overlapped with each other, and an input / output terminal of the first printed circuit board and an input / output terminal of the second printed circuit board are electrically connected to each other. Substrate. 2. The dielectric filter substrate according to claim 1, wherein the dielectric constant of the second printed circuit board is smaller than that of the first printed circuit board. 3. The dielectric filter substrate according to claim 1, wherein the thickness dimension of the second printed circuit board is larger than the thickness dimension of the first printed circuit board. 4. The dielectric filter substrate according to claim 1, wherein a dielectric loss tangent of the second printed board is smaller than a dielectric loss tangent of the first printed board. 5. A dielectric filter comprising: the dielectric filter substrate according to claim 1; and a dielectric resonator mounted on the dielectric filter substrate.