JPH01103001A - Dielectric filter - Google Patents

Abstract

PURPOSE:To miniaturize the title filter and to simplify the manufacturing process by forming plural resonators and forming plural through-holes in parallel in a dielectric block, and also, coupling each of these resonators by a lumped constant line. CONSTITUTION:In a dielectric block 2 made of ceramics of a dielectric filter 1 having a band elimination function, plural through-holes 3 are formed, and on the inside peripheral surface of each through-hole 3, an inner conductive film 4 is formed, and on a block outside face 2b and a bottom face 2c, an outer conductive film 5 and a conductive film 6 for short circuit are formed, which function as plural resonators 7. In each through-hole 3, a resin pin 8 which has metallic pin 9 in the center and functions as a coupling capacitor is inserted and fixed. Each pin 9 is connected by an air-core coil 10 being a lumped constant line. By selecting appropriately a constant of the coil 10 and the capacitor 8, the electric length between each resonator 7 can be set to lambda/4, therefore, the connection by a transmission line of lambda/4 length as before becomes unnecessary, and the aimed filter can be miniaturized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dielectric filter that functions as a band elimination filter, and in particular can reduce the external size and simplify the manufacturing process to reduce costs. The present invention relates to the structure of a dielectric filter.

[Conventional technology]

2. Description of the Related Art Conventionally, there are dielectric filters shown in FIGS. 8 and 9 that function as a band elimination filter that attenuates only signals in a specific frequency range. This dielectric filter 30 has a through hole 32 formed at the axis of a ceramic cylinder 31, and an end face 3 inside the through hole 32 and an open end side.
An inner conductive film 33. is provided on each outer surface except for 1a. Outer conductivity 1)
A capacitor 36 is formed by arranging a plurality of resonators 35 in parallel with each other and forming an electrode film on the bidirectional surface of a ceramic cylindrical body on the end face 31a side of the open end of the through hole 32 of each resonator 35. are electrically connected to each other, and the adjacent resonators 35 are connected via a capacitor 36 with a coaxial cable 37 having an electrical length of λ/4 wavelength.

[Problem that the invention seeks to solve]

By the way, the conventional dielectric filter 30 described above has a resonator 3
5 are connected to each other by a coaxial cable 37 having a length of λ/4 wavelength, which is a so-called distributed constant line. There is a problem that the outer shape of the filter 30 becomes large. In addition, the single resonator 35
Since it is a complicated task to prepare a plurality of λ/4 transmission lines and connect each one with a λ/4 transmission line, there is a problem in that it is time-consuming and increases the manufacturing cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dielectric filter that can reduce the external size of components, simplify the manufacturing process, and reduce costs.

[Means for Solving the Problems] The present invention provides a dielectric filter that functions as a band elimination filter, in which a plurality of through holes are formed in parallel in a dielectric block, and an inner groove is formed in the through hole. and forming a plurality of resonators by forming an outer conductive film on the outer surface excluding at least the end face on the open end side, and disposing a coupling member for capacitor coupling with the inner conductive film in the through hole. However, it is characterized in that adjacent coupling members are connected to each other by lumped constant lines.

Here, for example, an air-core coil or a pattern-forming coil can be adopted as the lumped constant line, and the capacitor coupling is realized, for example, by inserting a metal pin in the axial direction of the resin pin press-fitted into the through hole. can.

[゛effect]

According to the dielectric filter of the present invention, since each resonator is connected to each other by a lumped constant line, the connection length between the resonators can be significantly shortened, and the conventional single resonator can be Instead of the resonators being arranged in parallel with an interval equal to the length of the resonator, each resonator can be constructed into a single block, and the external size can be reduced accordingly.

In addition, since it is a lumped constant, it is possible to simplify the conventional complicated connection work that requires accurately ensuring the length of the line connecting the resonators, and there is no need to prepare multiple resonators. The labor and number of parts during production can be significantly reduced, reducing costs and improving productivity.

Here, the reason why the conventional distributed constant line can be replaced with a lumped constant line in the band elimination filter will be explained.

FIGS. 6(a-1) are equivalent circuit diagrams for explaining the process of establishing the present invention.

First, the λ/4 wavelength transmission line can be replaced by a lumped constant of a coil L and a capacitor C at a certain frequency f under the following conditions (Figure 6+a), (bl
reference).

ωLaZa・slnθ mc= (1/Za)tanθ/2 (Za: Characteristic impedance of the line, θ: Electrical angle of the line, ω-2πf) For example, f = 400 MIIZ, Z a-50Ω
, θ-90℃, L= (Za/2π・f)s inθ−507(2・π
・400XIO") X 1-1.99X10"
[H]C=(1/2g ・f−Za) tanθ/
'2-1/(2yr ・400 XIO' x50)
X 1 =7.958 xlO-” (Fl).

Therefore, the above transmission line is as shown in FIG.
It can be converted as shown in d).

Here, if the resonator is considered as an LC parallel resonant circuit, it is possible to convert dl into the equivalent circuit shown in FIG. 6 (tel).

In addition, in Fig. 6 (ei, C-C'-Ce (2C-
C'-Co) to perform Y-Δ conversion, and Figure 6(f) ~
(This is the equivalent circuit shown in the diagram.)

Then, C, - (CC″+C”Ce+CeC)/C”Ct =
(CC'+C'Ce+CeC)/C.

C,=(CC'+C'Ce+CeC)/C.

L"-L'-(1/ωt C1) Therefore, it can be expressed as an equivalent circuit as shown in FIG. 6(1), and as a result, the distributed constant line can be replaced with a lumped constant line.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 are diagrams for explaining a dielectric filter according to an embodiment of the present invention.

In the figure, 1 is a dielectric filter that functions as a band elimination in this embodiment. The dielectric block 2 of this dielectric filter 1 is made of rectangular parallelepiped ceramics, and the block 2 has five through holes 3 formed in parallel at regular intervals. An inner thick electrical film 4 is formed to cover the inner peripheral surface of. Further, on the four side surfaces 2b excluding the open end side end surface 2a and the bottom surface 2C of the dielectric block 2, an external field electric film 5. A conductive film 6 for shorting is formed to cover each of them. This short-circuiting conductive film 6 is used to short-circuit the inner and outer conductive films 4.5 to generate a resonance mode of λ/4 wavelength, thereby forming five resonators 7.

Further, a resin pin 8 is press-fitted into each through hole 3 on the open end side end surface 2a side. Furthermore, a metal pin 9 as a coupling member for capacitor coupling with the inner thick electrical film 4 is inserted and fixed in the center of the resin pin 8 in the axial direction thereof, and the upper part of the metal pin 9 is open. It protrudes above the end surface 2a.

The adjacent metal pins 9 are connected to each other by air-core coils 10 as lumped constant lines.

Next, the effects of this embodiment will be explained.

Since the dielectric filter 1 of this embodiment functions as a band elimination filter that attenuates only signals in a specific frequency range, it can be used, for example, as an antenna duplexer or a single-wavelength duplexer that combines two or more of the filters 1. Adopted.

In this way, according to the dielectric filter 1 of this embodiment, since the adjacent resonators 7 are connected to each other by the air-core coil 10 via the metal pins 9, the conventional distributed constant line is replaced with a lumped constant line. Therefore, instead of multiple single resonators connected in parallel in the past, it is possible to fit them into one block, and the connection length between the resonators 7°7 can be significantly reduced compared to conventional transmission lines. Can be made smaller.

In addition, the complicated connection work required to ensure the conventional λ/4 electrical length can be omitted, making the connection work that much easier. Furthermore, since only one block body needs to be prepared, the manufacturing process is simplified. This can reduce costs and improve productivity.

Here, in the above dielectric filter 1, by replacing the transmission line with a lumped constant, the generated capacitance can be absorbed by the resonator, but this is only a theory, and in reality, all Therefore, as shown in Figure 3+a) and (b),
A glue actance element Z for fine adjustment of filter characteristics is provided between the connection part between the metal pin 9 and the air-core coil 10 and the outer conductor 5.
In this case, this reactance element Z
may be added to all or arbitrarily selected connections, and capacitive and inductive types may be provided alone or in combination.

Further, in the dielectric filter I, fringing capacitance is generated on the open end side end surface 2a of the inner thick electric film 4 of the resonator 7.
Although capacitive coupling may occur between adjacent resonators 7,
This is the air core coil l mentioned above.

It can be absorbed by changing the value of .

In the above embodiment, the air-core coil 10 is provided on the lumped constant line.
Although the explanation has been given by taking as an example the case where the air-core coil 10 is adopted, for example, the one shown in FIG. 4 may be adopted instead of the above-mentioned air-core coil 10. In this example, the metal pin 9 is passed through the substrate 15, and the metal pin 9 and the coil line 16 are soldered. Even in this case, the same effects as in the above embodiment can be obtained.

Further, in the above embodiment, the metal pin 9 is used for capacitor coupling, and as shown in FIG. A capacitor member 13 formed by forming the capacitor member 12 may be employed. In this case, insert the metal column capacitor stand 14 into the through hole 3, connect the lower surface of the capacitor member 13 to the upper surface of this capacitor stand 14, and connect the air core coil IO to the upper surface of this capacitor stand 14. good.

Furthermore, the dielectric filter 1 of this embodiment can be connected in series with another filter, and this series body can be housed in a case to be used in the above-mentioned duplexer. Furthermore, the conventionally known bandpass filter 21 and the dielectric filter 1 of this embodiment can be integrally formed in one dielectric block 20.

Furthermore, in the above embodiment, a λ/4 wavelength resonator was taken as an example, but the present invention can also be applied to a λ/2 wavelength resonator.

〔Effect of the invention〕

As described above, according to the dielectric filter according to the present invention,
A plurality of through holes are formed in a dielectric block, inner and outer groove electrical films are formed inside and on the outer surface of the through holes, respectively, to form a resonator, and adjacent resonators are connected together via a capacitor coupling member. Since the connection is made by a constant line, the connection length between the resonators can be shortened, and a plurality of resonators can be integrated into one block body, which has the effect of allowing the size to be reduced accordingly.

Furthermore, it is possible to eliminate the need for complicated work while ensuring a predetermined electrical length, thereby greatly reducing the labor involved in manufacturing, as well as reducing the number of parts and reducing costs accordingly.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining a dielectric filter according to an embodiment of the present invention, and FIG. 1 is a perspective view thereof;
FIG. 2 is a partially sectional side view, FIG.
Figures (a) and 4) are a plan view and a side view showing a modification of the above embodiment, respectively, Figure 5 is a sectional side view showing another modification, and Figures 6 (fat to 6 (1) ) are equivalent circuit diagrams for explaining the process of establishing the present invention, FIG. 7 is a perspective view showing an example in which the dielectric filter and bandpass filter of the above embodiment are integrally molded, and FIGS. 8 and 9. are an equivalent circuit diagram and a perspective view, respectively, showing a conventional dielectric filter. In the figure, 1 is a dielectric filter, 2 is a dielectric block, 2a is an end face on the open end side, 3 is a through hole, 4 is an inner groove electric film, and 5 is a dielectric block.
Reference numeral denotes an outer groove electrical film, 7 a resonator, 8 a resin pin, 9.13 a metal pin, a capacitor member (coupling member), and 10.16 an air-core coil and a coil line (lumped constant line).

Claims (3)

[Claims] (1) In a dielectric filter that functions as a band elimination filter that attenuates only signals in a specific frequency range, a plurality of through holes are formed in parallel in a dielectric block, an inner conductive film is formed in the through holes, and , an outer conductive film is formed on at least the outer surface of the dielectric block to form a plurality of resonators, a coupling member for capacitor coupling with the inner conductive film is disposed in the through hole, and adjacent coupling members are connected to each other. A dielectric filter characterized in that: are connected by a lumped constant line. (2) The dielectric filter according to claim 1, wherein the lumped constant line is an air-core coil. (3) The dielectric material according to claim 1, wherein the capacitor coupling is realized by inserting a metal pin in the axial direction of a resin pin press-fitted into the through hole. filter.