JPS6272201A - Filter device - Google Patents

Abstract

PURPOSE:To eliminate surely a spurious radiation over a wide band with small size by inserting an axial low-pass filter for eliminating a spurious radiation between a filter element in a case and an input/output port mounted to the case outer wall. CONSTITUTION:The axial low-pass filter 1 consists of an outer conductor 3 having an axial hole 2, a capacitor 4, an inductor 5 and a center conductor 6. The capacitor 4 and the inductor 5 are inserted alternately along the axial direction in the inside of the hollow outer conductor 3. The capacitor 4 consists of an outer capacitor electrode being the outer conductor 3 and a cylindrical inner capacitor electrode 8 fitted to the inside of he cylinder of a cylindrical dielectric 7, and the inductor 5 is connected to the electrode 8. The center conductor 6 is connected to each inductor 5 of the 1st stage and the final stage. When the dielectric coaxial resonator being a filter element is of 1/4 wavelength, since the axial low-pass filter 1 is constituted as the axial length of the same degree as that of the resonator, the axial low-pass filter 1 is assembled in the inside of the wall of the case 11 of the filter device or the space in the case in parallel with the resonator 10.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention mainly relates to a filter device using a dielectric coaxial resonator as a filter element, and more particularly to a filter device incorporating a low-pass filter having a spurious removal function. .

<Prior Art> In general, a filter device incorporates a plurality of dielectric coaxial resonators as filter elements and a coupling substrate in a case, and each resonance is connected to a plurality of capacitor electrodes formed on the coupling substrate. In addition to connecting the internal conductors of the container individually,
It is known that a coaxial connector is attached to the outer wall of the case as an input/output port.

<Problems to be solved by the invention> In the case of a filter device having such a configuration, for example, if the resonator incorporated as a filter element is of 1/4 wavelength type, odd harmonics of the fundamental wave, 172 wavelengths. If it is a type of waveform, the spurious suppression ratio of harmonics, which are integral multiples of the fundamental wave, will be inferior, which is a point that should be considered in terms of performance.

By the way, this type of filter device itself usually does not have a spurious removal function. Therefore, in such a filter device, by connecting a circuit component having a spurious removal function to the outside, I was trying to remove spurious signals. However, such a system requires circuit parts in addition to the original components of the filter device, resulting in an increase in the number of parts.

To deal with this, there are filter devices that incorporate a low-pass filter having a spurious removal function or a band cutoff filter as a spurious cutoff filter. As shown in FIGS. 11(A), (B), and (C), these have a structure in which a spurious band cutoff filter 4° is connected to a band pass filter 5°.

The low-pass filter usually looks like the one shown in Figure 10 (A).
B) Single or multiple dielectrics I, as shown in FIG. ,
Multiple capacitors C2° and C4 using 2o and 3o
゜, inductor L1゜, L3゜, L5. It has a structure in which the two are connected. However, with such a structure, electromagnetic waves easily leak, and it is necessary to provide a shielding function by some other means, and if it does not have a shielding function,
There is a problem that high frequency characteristics deteriorate.

Furthermore, the band-cut filter mainly utilizes a coaxial cable of a predetermined length to produce a trapping effect at a specific frequency. However, this band-cut filter 4° is
Spurious signals cannot be removed in bands other than the predetermined cutoff range.

In addition, there is a method that adds a grounded stray capacitance to the resonator, thereby shifting the spurious band.
In this scheme, the spurs are not significantly attenuated and therefore effective spurious removal cannot be desired.

As described above, conventional filter devices having a spurious removal function have problems in that the entire filter device becomes large in size or a sufficient spurious removal effect cannot be obtained.

In view of such conventional problems, the present invention miniaturizes a low-pass filter having a spurious removal function so that it can be incorporated into a dead space in a filter device, improves the high frequency characteristics of the low-pass filter itself, and further improves the high frequency characteristics of the low-pass filter itself. The purpose of the present invention is to obtain a small, inexpensive, and high-performance filter device that does not deteriorate the characteristics in the passband of the filter.

Means for Solving the Problems In the present invention, in order to achieve the above object, a filter element is built into the case, an input/output port is attached to the outer wall of the case, and the input/output port and the above-mentioned In a filter device electrically connected to a filter element, a sleeve-shaped low-pass filter is interposed between the filter element and an input/output port, and this shaft-shaped low-pass filter has the following features:
an outer conductor having an axial hole; a capacitor with a dielectric having a cylindrical cross section and using the outer conductor as an outer capacitor electrode; Like an inductor, it consists of a center conductor connected to the inner capacitor electrode of a capacitor.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

First, the configuration of a shaft-shaped low-pass filter to be incorporated into the filter device of the present invention will be explained based on FIGS. 1 to 3.

Figure 1 (A) is a configuration diagram of an axial low-pass filter;
B) is an equivalent circuit diagram thereof, and both figures show an inductor input type axial low-pass filter. The axial low-pass filter 1 includes an outer conductor 3 having an axial hole 2, a capacitor 4 whose dielectric has a cylindrical cross-section, for example, a cylindrical cross-section, an inductor 5, and a central conductor 6.

The outer conductor 3 is usually made of a metal such as an aluminum alloy, but it can also be made of an insulating material with an electrode film formed on the inner peripheral surface of the axial hole 2. It is sufficient that the inner circumferential surface portion of 2 is made of a conductor, and this conductor portion is connected to earth. Further, the outer conductor 3 is
In short, it is sufficient that it has the axial hole 2, and its external shape may be of any shape. The capacitor 1 and the inductor 5 are inserted alternately into the hollow interior of the outer conductor 3 along the axial direction. The capacitor 4 uses the outer conductor 3 as an outer capacitor electrode, and includes a cylindrical dielectric 7 that is internally fitted into the hollow interior of the outer conductor 3.
It is composed of a cylindrical (or cylindrical) inner capacitor electrode 8 that fits inside the cylinder of the dielectric 7. Further, the inductor 5 is connected to the inner capacitor electrode 8 inside the hollow of the outer conductor 3. In this embodiment, the center conductor 6 is connected to each of the first and last stage inductors 5.

FIG. 2(A) is a block diagram of a capacitor input type axial low-pass filter, and FIG. 2(B) is its equivalent circuit diagram. The outer conductor 3, capacitor 4, and inductor 5 in this embodiment may have the same structure as shown in FIG. is connected to the inner capacitor electrode 8.8. In any case, the capacitor and inductor are connected in a symmetrical circuit arrangement; however, the present invention is not limited to this, and they may be connected in an asymmetrical circuit arrangement.

FIG. 3 is a cross-sectional view showing the specific structure of the axial low-pass filter l, and this figure shows a five-stage axial low-pass filter of a capacitor top type.

In this embodiment, a plurality of (three stages in this example) capacitors 4. The dielectric material 71 constituting the components is a continuous, integral, long cylindrical body, and is made of a heat-shrinkable tube made of PTFE, polyester, or the like.

Second, an insulating rod 9 is inserted into the axial position of the inner capacitor electrode 8 of each capacitor 4, and an inductor is wound around the outer periphery of this insulating rod 9. One center conductor 6 is coupled to the inner capacitor electrode 8 of the first stage capacitor 4, and the other center conductor 6 is coupled to the inner capacitor electrode 8 of the last stage capacitor 4.
is coupled to the inner capacitor current [i8. Note that the same components as in FIG. 1(A) and FIG. 2(A) are denoted by the same reference numerals.

With this configuration, the portion of the shaft-shaped low-pass filter 1 excluding the outer conductor 3 is integrated into one shaft, which facilitates handling during assembly work and the like.

Next, the configuration of a filter device incorporating the above-described axial low-pass filter I will be explained based on the embodiments shown in FIGS. 4 to 6.

If the dielectric coaxial resonator, which is the filter element constituting the filter device, is of 1/4 wavelength, the axial low-pass filter l can be constructed with the same axial length as the resonator.
As shown in the schematic cross-sectional views of FIGS. 4(A) to (F),
The axial low-pass filter l can be installed parallel to the resonator 10 inside the wall of the case 11 of the filter device or in the space 12 in the case II.

That is, each of the embodiments shown in FIGS. 4(A) to 4(C) eliminates the wall portion of the case 11 that has conventionally been a dead space of the filter device, such as the partition wall portion between the resonator IO and the outer surface of the case 11. An axial hole 2 is formed in the partition between the resonators 10, and the axial hole 2 is used as an external conductor 3 of the axial low-pass filter l, and the axial low-pass filter l is inserted into the partition. This is what I did.

In addition, each of the embodiments shown in FIGS. 4(D) to F) uses a resonator IO, which is a dead space in a conventional filter device.
The space 12 between the outer wall of the case 11 and the resonator 1
Utilize the space 12 between the 0's, and in that space 12,
Axial low-pass filter l having a cylindrical outer conductor 31
is inserted.

FIG. 5 shows an example in which the axial low-pass filter 1 is incorporated into a single filter. A dielectric coaxial resonator IO as a filter element and a coupling substrate 13 are incorporated in the case 11, and the inner conductor of each resonator tO is connected to a plurality of capacitor electrodes formed on the coupling substrate 13. Coaxial connectors 14 and I4 are individually connected and installed as input/output ports on the outer wall of the case 11, and an axial low-pass filter l is installed between one coaxial connector 14 and the input/output electrode of the coupling board 13. is interposed.

An example of the operating state will be explained using the embodiment shown in FIG.

A signal from the input coaxial connector 14 (upper right in the figure) is transmitted to the first stage resonator IO via the capacitance between the input electrode on the coupling board 13 and the first stage capacitor electrode.
After being propagated to the resonator l of the next stage and the succeeding stage through the capacitance between each capacitor electrode on the coupling substrate 13,
The signal is propagated to O2..., inputted from the output electrode on the coupling substrate 13 to the shaft-shaped low-pass filter l, and the odd harmonic spurious harmonics of the fundamental wave included in the input signal are removed by this sleeve-shaped low-pass filter l. Thereafter, the signal is output to the outside from the output coaxial connector 14 (bottom left in the figure).

In this case, since the outer conductor 3, which is the outer peripheral portion, of the axial low-pass filter l is grounded, there is little leakage of IX magnetic waves, excellent high frequency characteristics, and spurious noise is removed over a wide band.

Note that the input and output directions are opposite to those described above, and the operation is the same.

FIG. 6 shows an example in which an axial low-pass filter l is incorporated in the duplexer. A plurality of dielectric coaxial resonators 10. ... and a coupling board 13 are incorporated, and the inner conductor of each resonator 10 is individually connected to the plurality of capacitors 1 formed on the coupling board 13 as poles, and the outer wall of the case II is connected to the outer wall of the case II. Each coaxial connector for antenna input/output, input only or output only 14. ..., and an axial low-pass filter l is interposed between the antenna coaxial connector 14 and the input/output electrodes of the coupling board 13. In this case, as shown in Fig. 1f (B), by using one LPF' in the common part of the two filters, the spurious of both filters is suppressed and the external size is reduced. It is a structure.

When the axial low-pass filter 1 is directly connected to the coaxial connector 14 as shown in the embodiments shown in FIGS. 5 and 6 above, as shown in the embodiments shown in FIGS. 7 to 9 below, First, the coaxial connector 14 and the axial low-pass filter 1 are integrated. In this case, it is preferable that the center conductor of the coaxial connector 14 and one of the center conductors 6 of the axial low-pass filter 1 be integrally formed.

The thickness of the outer wall of the case 11 is that of the axial low-pass filter l.
If the length in the axial direction is equal to the axial length of case 1, for example, when incorporating it into a die-cast case,
A shaft-like hole 2 is formed in the outer wall of the shaft-like low-pass filter 1, and a portion of the shaft-like hole 2 is used as an external conductor 3 of the shaft-like low-pass filter 1. A portion of the axial low-pass filter l excluding the outer conductor 3 is inserted into the axial hole 2 .

The thickness of the outer wall of the case 11 is that of the axial low-pass filter 1.
When the conductor is thin compared to the axial length of the conductor, for example, when it is incorporated into a sheet metal case, a cylindrical outer conductor 31 such as a conductor pipe is fitted onto the outside, as shown in FIG.

FIG. 9 shows a coaxial cable 15 connected to an axial low-pass filter 1.
is connected. In this example as well, a cylinder having a cylindrical external conductor 31 (in this figure, made of an insulating tube or the like with a conductive film formed on the inner peripheral surface) is used as the axial low-pass filter l.

In FIGS. 7 to 9, the internal elements of the axial low-pass filter l are omitted for the sake of simplicity.

<Effects of the Invention> As described above, according to the present invention, the low-pass filter for spurious removal is assembled into a shaft shape, which makes it compact, and the dead space of the conventional filter device is used to fill the area. The spurious removal function can be provided without changing the overall size of the conventional filter device.

In addition, since the outer peripheral portion of the axial low-pass filter for spurious removal is shielded, there is no leakage of electromagnetic waves, and the filter has excellent high frequency characteristics, allowing it to reliably remove spurious over a wide band.

Furthermore, axial low-pass filters have a structure similar to coaxial connectors and coaxial cables, and can be connected integrally with coaxial connectors.
Impedance matching can be achieved with the coaxial connector included.

In addition, since the axial low-pass filter has a simple structure, it is easy to manufacture, and a filter device having spurious removal absorption ability can be manufactured at low cost.

[Brief explanation of drawings]

1 to 3 relate to a sleeve-shaped low-pass filter used in the filter device of the present invention, FIG. 1(A) is a configuration diagram of the shaft-shaped low-pass filter, FIG. 1(B) is an equivalent circuit diagram thereof,
Figure 2 (A) is the configuration diagram of the Ike's Quiz axis [l-pass filter, Figure 2 (B): Yuso 5) Special 11i circuit diagram, Figure 3
The figure is a sectional view showing a specific structural example of an axial low-pass filter. 4 to 6 relate to a fl filter device incorporating the above-mentioned axial low-pass filter, and FIG. 4(A) to FIG.
(F) is a sectional view of the groove showing its assembled state, FIG. 5 is a partially cutaway plan view of the single filter device, and FIG. 6 is a partially cutaway plan view of the duplexer. 7 to 9 are cross-sectional views showing the embodiment, and FIGS. 10 and 11 relate to the conventional example, and FIG.
is a configuration diagram of a low-pass filter for spurious removal, No. 11
Figures (A>(B) and (C) are block diagrams of filter devices having spurious cutoff filters. 1. Ah-shaped low-pass filter, 2. Axial hole, 3. External conductor, 4. Capacitor, 5.・Inductor, 6...
Center conductor, 7. Dielectric, 8. Inner capacitor electrode, 10. Dielectric coaxial resonator (filter element), II...
·Case. Mr. Oka Representative of Murata Manufacturing Co., Ltd. Patent attorney Mr. Oka 1) Kazuo
Figure 5, Figure 6, Figure 7, Figure 8, Figure 9, Figure 10 (A)':) O40 Procedural Amendment Letter Patent Office Commissioner Sir 1, Indication of Case Patent Application No. 211891 of 1985 No. 2, Name of the invention filter device 3, Relationship with the person making the amendment Patent applicant address 2-26-10 Tenjin, Nagaokakyo City, Kyoto Name (
623) Mura Co., Ltd. 1) Manufacturer's initiative 5. Number of inventions increased due to amendment 7. Contents of amendment (1) On page 4, line 2 of the specification, it says "spurious TD cutoff filter", then r (SEF) Join J. (2) In the 6th line from the bottom of page 8, the word "top" should be corrected to "input." (3) Delete "odd harmonics of the fundamental wave" in the last line of page 11. (4) In the 1st line of page 13, correct rLPFJ to "low-pass filter."that's all

Claims (4)

[Claims] (1) In a filter device in which a filter element is built into a case, an input/output port is attached to the outer wall of the case, and the input/output port and the filter element are electrically connected, the filter element and the input/output port are electrically connected. A shaft-shaped low-pass filter is interposed between the output port and the shaft-shaped low-pass filter includes an outer conductor having a shaft-shaped hole, a capacitor whose dielectric body has a cylindrical cross section, and the outer conductor is an outer capacitor electrode. A filter device comprising: an inductor connected to an inner capacitor electrode of a capacitor in the hollow interior of the outer conductor; and a center conductor connected to the inductor or the inner capacitor electrode of the capacitor. (2) The filter device according to claim 1, wherein the wall portion of the case in which the axial hole is formed also serves as an external conductor of the axial low-pass filter. (3) The filter device according to claim 1 or 2, wherein the input/output port is a coaxial connector, and the coaxial connector and the axial low-pass filter are directly connected and integrated. (4) The filter device according to claim 1, 2, or 3, wherein the dielectric material is a heat-shrinkable tube.