JPS62136103A - Dielectric filter - Google Patents

Abstract

PURPOSE:To make spurious radiation hardly caused around a dielectric block by forming a through hole to a part on a shield wall opposed in both sides of the dielectric block in the lengthwise direction and in crossing with a symmetrical center line of the dielectric block and leading out input/output leads through the through hole. CONSTITUTION:A shield case 2 is used to cover an open end face 1a of the dielectric block 1, an L-shaped angle steel is sued to form shield walls 21a, 21b opposed to each other in both sides of the dielectric block 1 in the lengthwise direction. The through hole 23 to lead out the input/output lead 19 externally is formed on the shield walls 21a, 21b while the case 2 is assembled to the dielectric block 1 in the part crossing with the symmetrical center line of the dielectric block. Since the input/output lead 19 connected to the coupling means of the dielectric block 1 is led through the through hole 23 on the shield case wall face on the symmetrical center line, the spurious radiation is prevented including the input/output lead 19 and the shield case 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a dielectric filter, particularly a dielectric block in which through holes are formed in a row, and a conductive film on at least four outer surfaces of the through holes and on the inner surfaces of the through holes. A resonant unit is formed by these conductive films and a dielectric block between both conductive films, and resonant units are located near both ends in the longitudinal direction of the open end surface, which is the outer surface of the dielectric block where the conductive film is not formed. The present invention relates to a dielectric filter including an external coupling means for coupling with the coupling means, an input/output cathode led out from the coupling means, and a shield case covering the open end surface.

In the above dielectric filter, as the number of stages of the resonance unit increases, the resonance frequency of the TEII mode becomes lower and approaches the resonance frequency of the TEM mode, which is the mode used, so the spurious of the L mode is reduced. arise. As a means to prevent such spurious signals, a technique has been proposed in which the external coupling structure of the dielectric block is improved (Japanese Patent Laid-Open Publication No. 116201/1982).

Incidentally, when a dielectric filter is actually used, the input and output cathodes can be fully extended for coupling with an external circuit, and the open end surface of the dielectric block is covered with a shielding case. In the microwave band where dielectric filters are used, the input/output cathodes and the shield case also become elements of the three-dimensional circuit. Therefore, even if spurious radiation within the dielectric block can be prevented by the conventional means described above, spurious radiation may occur depending on the surrounding input/output cathodes and shield conditions.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a dielectric filter that is devised so that spurious waves are less likely to occur around the dielectric block including the input/output cathodes and the shield case.

5. In order to achieve the above-mentioned object of solving the problem, the present invention forms through holes in the portions of the opposing shield walls on both longitudinal sides of the dielectric block that intersect with the center line of symmetry of the dielectric block. The device is characterized in that the input/output cathode connected to the external coupling means is led out through this through hole.

Here, the symmetry center line refers to an arbitrary horizontal line on a vertical plane along the longitudinal direction that bisects the dielectric block.

When the Saku-Ichiri dielectric filter functions as a filter, a displacement current flows within the dielectric block. In this case, near the end of the dielectric block near the external coupling means,
The direction of input and output cathodes influences the distribution of displacement current. That is, if the lead-out direction of the lead cathode deviates from the center line of symmetry of the dielectric block, the density of the displacement current is high in the direction along the lead, and the density of the displacement current is low in the opposite direction. Therefore, the distribution of the displacement current will be biased on both sides of the center line of symmetry.

It is known that such a bias in the mainstream distribution allows spurious excitation of the TE 7-de.

On the other hand, if the input and output cathodes are led out of the shield case along the symmetry center line, the displacement current will be distributed such that the current density is maximum in the direction along the input and output cathodes, but the distribution of displacement current in this case is symmetrical. It is symmetrical with respect to the center line, and as a result does not allow excitation of spurious T, E 11 modes.

According to the present invention, a through hole is formed in the portion of the shield wall that intersects with the center line of symmetry of the dielectric block, and the input and output cathodes are guided to the outside through this through hole.
Inside the shield case, the input and output cathodes can be wired along the center line of symmetry, making it possible to effectively prevent spurious radiation.

1 is a vertical sectional view of a dielectric filter as an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line A-A in FIG. Block, 2 is shield case, 3
is a cover.

The dielectric block 1 is a cube made of, for example, a titanium oxide ceramic dielectric, and has a plurality of through holes 11 inside.
... are formed in a line approximately along the center line of symmetry. A conductive film 12 is formed on the inner surface of each through hole 11.
is formed (hereinafter, the conductive film on the inner surface of the through hole is referred to as an inner conductor). On the other hand, a conductive film 13 is formed on all four sides of the outer surface of the dielectric block 1 (hereinafter, this conductive film is referred to as an outer conductor). Then, this outer conductor 13 and the inner conductor 12
is the conductive film 1 formed on the bottom surface 1b of the dielectric block l.
4 is shorted. Therefore, the inner and outer conductors 12
．． 13 and the dielectric block l between them.
It constitutes a resonant unit that performs wavelength resonance. The resonant frequency of the resonant unit is determined by the electrical length of the inner conductor 12 or outer conductor 13.

Incidentally, the electrical length may be A wavelength as in this example, or
It can also be a wavelength. In the case of two wavelengths, the conductive film 14 on the bottom surface of the dielectric block 1 is unnecessary. Each of the resonance units is
They are coupled by coupling holes 15 formed between the through holes 11. However, in addition to coupling holes, a known coupling structure can be used to couple each resonance unit.

On the other hand, coupling capacitors 16 are provided as an example of external coupling means near both longitudinal ends of the open end surface 1a, which is the upper surface of the dielectric block 1 on which no conductive film is formed.

More specifically, the 100 holes 1 near both ends of the dielectric block 1
A metal column-shaped mounting member 17 is inserted into 1 and connected to the inner conductor 12, and one capacitor electrode 18a is attached to this mounting member 17.
A coupling capacitor 16 is provided in a state in which the two are connected. The input/output cathode 19 is connected to the other capacitor +118b of this capacitor 16. Note that the external coupling means is not limited to the coupling capacitor described above, and any known coupling means may be used.

The shield case 2 is for covering the open end surface 1a of the dielectric block 1, and in this embodiment, an L-shaped angle member is used. As shown in FIG. 3, a part of the side wall 21 of the L-shaped angle member is cut and raised to form opposing shield walls 21a and 21b on both sides of the dielectric block 1 in the longitudinal direction. The edges of both shield walls 21a, 21b and the upper wall 22 of the shield case are bonded with solder as shown by S in the figure, and the L-shaped angle member is reinforced by the shield walls. On the shield walls 21a and 21b, in a portion that intersects with the center line of symmetry of the dielectric block when the shield case 2 is assembled to the dielectric block 1, there is a transparent hole for guiding the input/output cathode 19 to the outside. A hole 23 is formed. Furthermore, input/output cathode bins 25 are inserted through insulators 24 on both sides of the upper wall 22 in the longitudinal direction and located outside of the shield walls 21a and 21b. This input/output cathode bin 25 does not necessarily need to be located on the center line of symmetry of the dielectric block.

The shield case 2 has a side wall 21 along one longitudinal side of the dielectric block 1, and the shield wall 21
The shield walls 21a and 21b are positioned by placing them along both side surfaces perpendicular to the longitudinal direction of the dielectric block, and in this state, the side walls 21 are cut and raised by cutting and raising the shield walls 21a and 21b.
As shown in FIG. 4, the edge of the opening 21C formed in the dielectric block 1 is assembled to the dielectric block 1 by attaching it to the outer ring plate 13 of the dielectric block 1. After completing the assembly of this shield case 2, the other end of the input/output cathode 19, one end of which is connected to the coupling capacitor 16, is connected to the fifth
As shown in the figure, it is led out through through holes 23 formed in the shield walls 21a and 21b, and connected to the input/output cathode bin 25.

As shown in Fig. 6, the cover unit 3 is a metal case with an open top side, and the side wall has holes 31 for soldering in multiple places.
... is formed. Furthermore, a projection 32 is formed on the upper edge of the integrated cover 3 to allow the dielectric filter to be assembled to a printed circuit board (not shown) or the like while the dielectric filter is housed therein. The dielectric block 1 with the shield case 2 assembled thereon is inserted into the cover unit 3, and the gap between the opening edge of the cover 3 and the shield case 2 is sealed with solder.

The frequency characteristics of the dielectric filter assembled as described above are as shown by the broken line in FIG.

The solid line indicates the frequency characteristics of the conventional dielectric plate filter, and as is clear from comparing both characteristic curves, spurious radiation is significantly reduced in the dielectric filter of this embodiment.

Incidentally, in the above embodiment, an L-shaped angle material is used as the shield case 2, but the present invention is not limited to this, and a case with an open bottom as shown in FIGS. 8 and 9 may be used. You can also do it. In this case, the housing 2 is fixed by soldering to the outer conductor 13 of the dielectric block.

However, it is preferable to use an L-shaped angle member as the shield case 2 as in the first embodiment for the following reasons. That is, when an L-shaped angle member is used, the height of the upper wall 22 is defined by the side wall 21, and the distance between the open end face of the dielectric block and the earth wall of the L-shaped angle member is constant over the entire open end face. As a result,
After adjusting the characteristics of the dielectric filter, there is an advantage that the characteristics will not change easily even if other metal materials are brought close to it, such as by storing it in the cover 3.

Further, the through hole 23 formed in the shield case 2 may be any hole as long as it is located on the center line of symmetry and allows insertion of the input and output cathodes, and may be a notch or notch as shown in FIG. 10, for example.

Furthermore, a connector 26 may be attached to the through hole 23 as shown in FIG. 8.9, and the input/output cathode 19 may be connected to the inner conductor 27 of the connector 26, thereby connecting to an external circuit through the connector 26. In this case, the inner conductor 27 of the connector also forms part of the input/output cathode 19.

In the present invention, as explained above, the input and output cathodes connected to the coupling means of the dielectric block are led out through the through hole in the wall of the shield case located on the center line of symmetry, so the input and output cathodes and the shield case are In addition, spurious radiation can be effectively prevented, and a dielectric filter can be provided which has a high usability value.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing a dielectric filter as an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA in FIG.
, 5.6 are diagrams explaining the procedure for assembling the dielectric filter, FIG. 7 is a diagram showing the frequency characteristics of the dielectric filter, and FIG. 8 is a dielectric filter as another embodiment of the present invention. FIG. 9 is a partially cutaway sectional view of the filter, and FIG. 10 is a diagram showing another example of a through hole formed in a shield wall that can be implemented in the present invention. l...Dielectric block, 1a...Open end surface 2...
Shield case, 11...through hole 12.13.14.
...Conductive film, 16...Coupling means 19.26.27...
・Input/Output cathodes 21a, 21b...Shield wall, 23...Through hole Patent applicant Murata Manufacturing Co., Ltd. Figure 1 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Full circle pattern Figure 8 Figure 10

Claims (1)

[Claims] Conductive films are formed on at least four outer surfaces of a dielectric block in which through holes are formed in a row and on the inner surface of the through holes, and these conductive films and the dielectric block between the two conductive films External coupling means for coupling with the resonance unit is provided near both ends in the longitudinal direction of the open end face, which is the outer surface of the dielectric block on which the conductive film is not formed, constituting the resonance unit, and the input and output cathodes are connected to the outside from the coupling means. At the same time, in the dielectric filter having the open end face covered with a shield case, a through hole is formed on the opposing shield walls on both sides in the longitudinal direction of the dielectric block at a portion that intersects with the center line of symmetry of the dielectric block. A dielectric filter characterized in that an input/output cathode formed therein and connected to an external coupling means is led out through the through hole.