JPH0870202A - Dielectric filter and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Purpose] To eliminate unnecessary capacitance and reduce insertion loss. [Constitution] The connection terminal 14 is an internal conductor connecting portion 14a for electrically connecting to the internal conductor of the coaxial resonance element 11.
And a coupling element connecting portion 14b branching from the internal conductor connecting portion 14a and connecting the electric coupling elements 15, 16 and 17, and the coaxial resonance element 11 including the connection terminal 14 are adjacent to each other. A plurality of such electric coupling elements are arranged, and the electric coupling elements 15, 16 and 17 are sandwiched and connected between the coupling element connecting portions 14b of the connection terminals 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication device, and more particularly, to a dielectric filter used in mobile communication devices such as car telephones, mobile phones and the like which use microwaves of several hundred MHz to several GHz. And a manufacturing method thereof.

[0002]

2. Description of the Related Art As an example of a conventional dielectric filter, a structure of a bandpass filter using two coaxial resonance elements using a dielectric having a square pole shape (or a cylindrical shape) is shown in FIG. These coaxial resonance elements 11 are grounded in parallel on the ground conductor 12. The coaxial resonance element 11 has a penetrating portion formed in its axial direction.
An internal conductor 13 is provided in the penetrating portion. A plate-shaped connection terminal 51 is connected to the internal conductor 13. Also,
An outer conductor (not shown) is provided on the outer surface of the coaxial resonance element 11.

A wiring board 52 is provided on the ground conductor 12. On the wiring board 52, three electric coupling elements 15 for coupling a plurality of coaxial type resonance elements 11,
16, 17 are provided. Electrical coupling element 15, 1
6 and 17 are electrically connected to the conductor pattern 53 formed on the wiring board 52 by means such as soldering.

Further, the input / output terminals 18 are connected to both sides of the conductor pattern 53 in the longitudinal direction. By connecting the input / output terminals 18 to the conductor pattern 53, a filter is formed between the input / output terminals 18. To be done.

In FIG. 5, the electric coupling elements 15, 16,
Although the case where a capacitor is used in 17 is shown, other electric coupling elements such as a coil may be used.

FIG. 6 shows a circuit configuration of the dielectric filter shown in FIG. As a specific example, the resonance frequency of the two coaxial resonance elements 11 is set to 1490 MHz (εr = 90, 3
The capacitance of the electric coupling elements (capacitors) 15 and 17 provided on both sides is 0.71 pF, and the capacitance of the electric coupling element (capacitor) 16 provided in the middle is 0.31 pF. The wiring board 52 is 10 mm ×
5mm × 1.0mmt glass epoxy resin (εr =
4.5) was used.

In the graph shown in FIG. 7, the solid line shows the frequency characteristic of this dielectric filter. According to this, the center frequency fo = 1490 MHz, the pass bandwidth BW
= 20 MHz, insertion loss 3.1 dB, fo-50 MHz
It can be seen that the attenuation amount at is about 20 dB. Further, in the graph shown in FIG. 7, the broken line shows the design value of this dielectric filter, but the actual filter characteristics are wavy in the vicinity of the pass band as compared with the design values.
Insertion loss is also large. Also, it can be seen that the amount of attenuation on the low frequency side is small, and it is largely deviated from the design value as a whole.

The dielectric filter is required to have a small insertion loss in the pass band and a large amount of attenuation in selectivity.

However, in the development of the dielectric filter, it is desirable that the actual filter characteristics agree well with the designed values. In terms of production, cost reduction is desired by reducing the number of parts.

[0010]

However, according to the prior art, the electrical coupling elements 15, 16 and 17 for coupling the plurality of coaxial resonance elements 11 to each other are formed on the wiring board 52.
It is electrically connected to the conductor pattern 53 formed above. The wiring board 52 is usually an insulator having a dielectric constant of about 4 to 5, and therefore, the conductor pattern 53 on the wiring board 52.
A coupling capacitance is generated between the ground plane and the ground plane or another conductor pattern.

8 and 9 conceptually show the capacitance of the wiring board. FIG. 10 shows a circuit configuration diagram including unnecessary coupling.

With reference to FIG. 8, for example, even if three coupling capacitors C1, C2 and C3 are connected on the substrate as designed, the conductor patterns 81 and 82 of the substrate, the conductor patterns 82 and 83 of the substrate, Substrate conductor patterns 83 and 84
Due to the capacitances Ca, Cb and Cc (unnecessary coupling capacitance due to the wiring substrate 52) between them, the capacitance of the coupling portion is actually C1.
+ Ca, C2 + Cb, C3 + Cc.

Further, referring to FIGS. 9 and 10, the capacitances Cd, Ce, Cf and Cg between the conductor patterns 81, 82, 83 and 84 on the wiring board 52 and the ground plane 90, and the conductor patterns are also provided. Since capacitance coupling such as capacitances Ch and Ci between 81 and 83 and conductor patterns 82 and 84 occurs, a circuit different from the design is actually configured.

As described above, even if a coupling element value as designed is used for these unnecessary capacitive couplings, a deviation from the designed value occurs, or a circuit configuration different from the design causes insertion loss and attenuation. There is a problem that is deteriorated compared to the design value.

Further, when the Q value of the wiring board 52 is low, the loss in the wiring board 52 is large and the insertion loss of the filter is large. Therefore, it is necessary to use a wiring board having a high Q value. The high wiring board 52 is generally expensive.

Therefore, an object of the present invention is to eliminate the unnecessary capacitance generated between the conductor patterns on the wiring board by not using the wiring board for connecting the electric coupling element, and to make the dielectric material well match the design value. To provide a filter.

Another object of the present invention is to provide a dielectric filter which eliminates the loss in the wiring board and has a small insertion loss.

Another object of the present invention is to provide an inexpensive dielectric filter which reduces the cost of the wiring board.

[0019]

According to the present invention, there is provided a dielectric filter including a plurality of coaxial resonance elements and an electrical coupling element for electrically coupling the coaxial resonance elements, the dielectric filter comprising: It has a connection terminal connected to an internal conductor provided in a penetrating portion of the coaxial resonance element, the connection terminal being an internal conductor connection portion electrically connected to the internal conductor, and branching from the internal conductor connection portion. A plurality of coaxial type resonance elements having the connection terminals are arranged adjacent to each other, and the electric coupling element is provided between the coupling element connection portions of the connection terminals. A dielectric filter is obtained which is characterized in that it is sandwiched and connected to each other.

According to the present invention, the connection terminal is
It is possible to obtain a dielectric filter having a supporting portion that connects the internal conductor connecting portion and the electric element connecting portion to each other.

Further, according to the present invention, a plurality of coaxial resonance elements having the connection terminals are arranged adjacent to each other, and the electric coupling elements are supported so as to be sandwiched between the electric element connection portions. A method for manufacturing a dielectric filter is provided, which is characterized in that the support is removed after being disposed above and electrically connecting the electric coupling element to the electric element connecting portion.

[0022]

According to the dielectric filter of the present invention, capacitive coupling occurs through the insulator, but the magnitude thereof is proportional to the dielectric constant of the insulator. Capacitive coupling occurs in the conductor pattern on the wiring board. However, since the wiring board used usually has a large dielectric constant of 4 to 5, the capacitive coupling is also large.

On the other hand, an electric coupling element for coupling a plurality of coaxial resonance elements is provided in each space without using a wiring board, especially in a structure in which the electric coupling element is supported in space. If the capacitive coupling is connected to the internal conductor of the type resonance element, the unnecessary capacitive coupling is through the air (dielectric constant 1), so that the unnecessary capacitive coupling can be reduced to 20 to 30%.

[0024]

FIG. 1 shows an embodiment of the dielectric filter of the present invention. FIG. 2 shows the connection terminal 14 used in the dielectric filter of FIG. In this embodiment, the same parts as those of the related art of the dielectric filter shown in FIG. 5 will be described with the same reference numerals.

Referring to FIG. 1, the dielectric filter includes two coaxial resonance elements 11 and these coaxial resonance elements 1.
Electrical coupling elements 15, 16 for electrically coupling 1
It is equipped with 17. In addition, the number of the coaxial resonance elements 11 may be two or more.

The coaxial resonance element 11 is grounded on the ground conductor 12. The coaxial resonance element 11 has a penetrating portion formed in its axial direction. On the ground conductor 12, three electric coupling elements 15, 16 and 17 for coupling a plurality of coaxial resonance elements 11 are provided. By connecting the input / output terminals 18 to the two electric coupling elements 15 and 17 provided on both sides, a dielectric filter is formed between the input / output terminals 18.

In FIG. 1, the electric coupling elements 15, 16,
Although the case where a capacitor is used in 17 is shown, other electric coupling elements such as a coil may be used.

The connection terminal 14 is a metal conductor, and as shown in FIG. 2, a cylindrical inner conductor connecting portion 14a for electrically connecting to the inner conductor formed in the penetrating portion of the coaxial resonance element 11. And a coupling element connecting portion 14b extending to one end side of the inner conductor connecting portion 14a and branched into two for connecting an electric element, and a support connecting one end of the inner conductor connecting portion 14a and the coupling element connecting portion 14b to each other. And a portion 14c.

The coupling element connecting portion 14b is the inner conductor connecting portion 1
4a extends in a direction orthogonal to the tube axis of 4a, and both end portions are bent at a right angle. Coaxial type resonance element 11
Are arranged so as to be adjacent to each other, and are further connected so as to sandwich the electric coupling elements 15, 16 and 17 between the connection terminals 14.

The connection terminal 14 is made of a conductor such as phosphor bronze or brass. Electrical coupling elements 15, 16,
Reference numeral 17 is electrically connected to the coupling element connection portion 14b by means such as direct soldering. In addition, the connection terminal 14 is 0.
It is formed of a phosphor bronze plate having a thickness of 1 mm, and is plated with solder. As a specific example of the connection terminal 14, the inner conductor connecting portion 14a has a pipe diameter of 0.8 mm and a pipe length of 3 mm.
The horizontal width dimension of the coupling element connection portion 14b is 2.6 mm, the vertical width dimension is 1 mm, and the longitudinal dimension of the support portion 14c is 2 mm.

As a concrete example, the electric coupling elements 15, 16 and 17 were electrically connected using the circuit configuration and the element values by the same design as described in the prior art.

FIG. 3 is a graph showing the characteristics of the dielectric filter according to the present invention. In FIG. 3, the characteristic of the dielectric filter is shown by a solid line. According to this, the center frequency is 149
0 MHz, bandwidth BW = 12 MHz, insertion loss is 2.5
The amount of attenuation at dB, fo-50 MHz is about 27 dB.

The characteristic indicated by the broken line in FIG. 3 is a design value, but the dielectric filter according to the present invention is in good agreement with the design value as compared with the conventional dielectric filter, and the insertion loss is 3.1 dB of the conventional one. It is improved by 0.6 dB, and the attenuation is f
27 dB from 20 dB in the past at o-50 MHz
It has been improved by dB.

Next, a method of manufacturing the dielectric filter of the present invention will be described. 4 (a), 4 (b) and 4
Steps of the manufacturing method are sequentially shown in (c).

First, as shown in FIG. 4A, two coaxial resonance elements 11 in which the connection terminals 14 are electrically connected to the inner conductor 13 are arranged adjacent to each other, and the ground conductor 12 is electrically connected. Connect to each other. Then, as shown in FIG.
A support base 41 for supporting the electric coupling elements 15, 16 and 17 is arranged immediately below the coupling element connection portion 14b of the connection terminal 14, and the electric coupling elements 15, 16 and 17 of the coupling element connection portion 14b facing each other are disposed. Place it so that it is sandwiched between them. That is, the electric coupling elements 15, 16 and 17 are sandwiched between the coupling element connecting portions 14b and are held at predetermined positions by the support base 41 on the ground conductor 12.

Next, the electric coupling elements 15, 16 and 17 are electrically connected to the coupling element connecting portion 14b by means of soldering or the like. After that, as shown in FIG. 4C, the support base 41 is removed from the ground conductor 12, and the input / output terminal 18 is connected to the two electric coupling elements 15 and 17 on both sides to obtain a dielectric filter. To be

In addition to the present embodiment, the coaxial resonance element 1
It is also possible to adopt a method in which the coupling element connecting portion 14b and the input / output terminal 18 are previously subjected to soldering or the like, and the supporting base 41 is used to simultaneously connect the respective members by reflow soldering or the like.

[0038]

As described above with reference to the embodiments, according to the dielectric filter and the method of manufacturing the same of the present invention, since the wiring board for connecting the electric coupling element is not used, the conductor on the wiring board is not used. It is possible to eliminate the unnecessary capacitance generated between the patterns and realize a dielectric filter that matches the design value well.

Since there is no loss in the wiring board, it is possible to provide a dielectric filter with a small insertion loss.

Further, since there is no wiring board, the cost can be reduced as a whole, so that an inexpensive dielectric filter can be provided.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a dielectric filter of the present invention.

FIG. 2 is a perspective view of a connection terminal used in the dielectric filter of FIG.

FIG. 3 is a graph showing frequency characteristic examples and design values of the dielectric filter of the present invention.

FIG. 4 shows a manufacturing process of the dielectric filter of FIG.
(A) is a perspective view showing a state in which a connecting terminal is connected to the coaxial resonance element, (b) is a perspective view showing a state in which an electric coupling element is provided from the state of (a), and (c) is a dielectric filter. It is a perspective view showing a completed product.

FIG. 5 is a perspective view showing a conventional dielectric filter.

6 is a circuit configuration diagram of the dielectric filter shown in FIG.

7 is a graph showing an example of frequency characteristics and design values of the dielectric filter shown in FIG.

FIG. 8 is a conceptual diagram showing an unnecessary capacitance generated in a wiring board in a conventional dielectric filter.

FIG. 9 is a conceptual diagram showing an unnecessary capacitance generated in a wiring board in a conventional dielectric filter.

10 is a circuit configuration diagram showing a circuit configuration including unnecessary coupling of FIG.

[Explanation of symbols]

 Reference Signs List 11 coaxial resonance element 12 ground conductor 13 inner conductor 14, 51 connection terminal 14a inner conductor connection portion 14b coupling element connection portion 14c support portion 15, 16, 17 electrical coupling element 18 input / output terminal 41 support base 52 wiring board 53, 81 , 82, 83, 84 Conductor pattern

Claims (3)

[Claims] 1. A dielectric filter including a plurality of coaxial resonance elements and an electric coupling element for electrically coupling the coaxial resonance elements, the dielectric filter being provided in a penetrating portion of the coaxial resonance element. An internal conductor connecting portion electrically connected to the internal conductor; and a coupling element connecting portion branched from the internal conductor connecting portion and connected to the electric coupling element. And a plurality of the coaxial resonance elements having the connection terminals are arranged adjacent to each other,
A dielectric filter, wherein the electric coupling element is sandwiched between the coupling element connecting portions of the connection terminals and connected to each other. 2. The dielectric filter according to claim 1, wherein:
The said connection terminal has the support part which mutually connected the internal conductor connection part and the said electric element connection part, The dielectric filter characterized by the above-mentioned. 3. The method of manufacturing a dielectric filter according to claim 1, wherein a plurality of coaxial resonance elements having the connection terminals are arranged adjacent to each other and sandwiched between the electric element connection portions. A method of manufacturing a dielectric filter, comprising: disposing the electric coupling element on a supporting base, electrically connecting the electric coupling element to the electric element connecting portion, and then removing the supporting base.