JPH07240602A - Dielectric filter - Google Patents

Abstract

PURPOSE:To provide an inexpensive dielectric filter having small insertion loss and good temperature characteristics by providing a case attachement part on the lower part of the flange of a case side bush. CONSTITUTION:To the cavity frame body 2 of a dielectric resonator, through the through holes of a cavity, cavity side bushes 4 and the case side bushes 5 are attached by screwing through toothed washers 6. The dielectric resonator to which the case side bushes 5 are attached is attached to a case lower plate 3 by inserting the case attachement parts of the case side bushes 5 to the through holes of the case lower plate 3 and tightening them by nuts. Characteristic adjustment screws such as a frequency adjustment screw 7 or a screw 8 for connection adjustment, etc., are screwed and attached to screw holes inside the case side bushes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric filter having a case in which a dielectric resonator having a dielectric resonator provided in a cavity is attached to a case.

[0002]

2. Description of the Related Art The structure of a conventional dielectric filter is shown in FIGS. In FIG. 3, reference numeral 1 is a TM double-mode dielectric resonator integrally molded in a cross shape, and 2 is a rectangular cylindrical cavity frame body integrally molded with the dielectric resonator 1. Side plates (not shown) are attached to the two opening surfaces of the cavity frame body 2, respectively. A conductor such as Ag is formed on the outer surface of the cavity frame body 2 and the inner surface or outer surface of the two side plates, and the cavity is formed by the cavity frame body 2 and the two side plates. A body resonator is constructed. The dielectric resonator 2 is formed with a frequency adjusting hole 1a into which the dielectric rod 7b of the frequency adjusting screw 7 is inserted. Two through holes for inserting the cavity side bushes 4, 4 are formed in the bottom surface of the cavity frame body 2 in the figure.

Reference numeral 3 denotes a case lower plate made of metal such as stainless steel, and through holes through which the cavity side bushes 4 and 4 are inserted are formed at positions corresponding to the through holes on the cavity side. The toothed washers 6, 6 are inserted between the cavity frame body 2 and the case lower plate 3, and the case side bushes 5, 5 are screwed into the cavity side bushes 4, 4 so that the bottom surface part of the cavity frame body 2 and the case The lower plate 3 is clamped and fixed together.

Then, a characteristic adjusting screw such as a frequency adjusting screw 7 or a coupling adjusting screw 8 is attached by being screwed on the inner peripheral surfaces of the case side bushes 5, 5, to adjust the frequency,
After the coupling adjustment, the nuts 11 are fixed. The frequency adjusting screw 7 comprises a resin screw portion 7a and a dielectric rod 7b attached to the tip of the screw portion 7a.
Is made of metal. The case main body 10 has its opening peripheral edge screwed to the peripheral edge of the case lower plate 3 with a screw 12.

FIG. 4 is a partially enlarged cross-sectional view showing the structure of a bush portion for sandwiching and fixing the cavity frame 2 and the case lower plate 3 shown in FIG. As shown in FIG. 4, the case-side bush 5 is a double screw made of Ag-plated metal, and the screw on the outer peripheral surface of the case-side bush 5 is screwed into the resin-made cavity-side bush 4. The cavity frame 2 and the case lower plate 3 are sandwiched. The toothed washer 6 inserted between the cavity frame 2 and the case lower plate 3 is made of Ag-plated ring-shaped metal, and the inner edge of the toothed washer 6 has teeth that form a plurality of vertically protruding portions. This is to ensure electrical continuity with the conductive film formed and formed on the outer surface of the cavity frame body 2 and to sandwich the mechanically and stably.

The screw hole inside the case side bush 5 is screwed into the screw portion 7a of the frequency adjusting screw 7 or the coupling adjusting screw 8. Frequency adjustment screw 7 or coupling adjustment screw 8
Is rotated, and the nut 11 is tightened at a predetermined frequency or degree of coupling to fix the frequency adjusting screw 7 or the coupling adjusting screw 8.

[0007]

However, in the structure as shown in FIG. 4 of the above-mentioned conventional example, the toothed washer is in direct contact with the case lower plate 3, and the outer surface of the dielectric resonator, that is, the cavity frame body. Part of the current flowing through the conductor on the outer surface flows out to the lower plate of the case via the toothed washer. The case lower plate is made of low-conductivity stainless steel, and there is a problem that the insertion loss of the dielectric filter is deteriorated by the conductor loss of the current flowing on the surface of the case lower plate.

Further, the dielectric resonator and the case lower plate must be attached by using the cavity side bush and the case side bush at the same time. Especially, when a plurality of dielectric resonators are attached to the case lower plate. Has a problem in that its workability is poor and the number of manufacturing steps is large, resulting in a high manufacturing cost.

Further, the case lower plate is sandwiched between the flanges of the case side bush, and the characteristic adjusting screw screwed to the inner peripheral surface of the case side bush fluctuates up and down due to the temperature change of the case lower plate. However, there is a problem that the temperature characteristics of the filter characteristics such as frequency are deteriorated.

Therefore, an object of the present invention is to solve the above problems of the conventional dielectric filter and to provide a case mounting portion under the flange of the case side bush, thereby making it inexpensive and having a small insertion loss. An object is to provide a dielectric filter having good temperature characteristics.

[0011]

In order to achieve the above object, the invention according to claim 1 of the present invention provides a dielectric resonator in which a dielectric resonator is housed in a cavity of either one of them. In a dielectric filter which is attached to a case using a cavity side bush into which a characteristic adjusting screw is inserted by being screwed onto the peripheral surface and a case side bush, a through hole is provided in a flat portion of the cavity and a predetermined position of the case. , The cavity of the dielectric resonator is inserted into the through hole of the cavity to attach the cavity side bush and the case side bush by screwing, and the case where the case side bush is attached to the dielectric resonator. The case-side bush is attached to the case by inserting the case-attaching portion of the case-side bush into the hole and tightening it with a nut.

The invention according to claim 2 is the invention according to claim 1, characterized in that a toothed washer is inserted between the cavity and the case side bush.

[0013]

According to the above construction, the current flowing through the conductor on the surface of the cavity of the resonator flows through the flange surface of the case side bush, so that the current flowing on the surface of the case with low conductivity and large conductor loss is It almost disappears. Further, after the case-side bush is attached to the resonator alone, the case-side bushed resonator alone can be attached to the case. Further, since the case is attached under the flange of the case side bush, it is possible to reduce the influence of the dimensional fluctuation of the case due to temperature change on the vertical fluctuation of the characteristic adjusting screw.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. In the figure, the same or corresponding parts and those having the same functions as those in the conventional example are designated by the same reference numerals.

The structure of the dielectric filter according to one embodiment of the present invention is shown in FIGS. 1 is a side view of the dielectric filter before mounting the side plate, and FIG. 2 is a partially enlarged sectional view showing the structure of the bush portion of FIG.

As shown in FIG. 1, the dielectric filter of this embodiment is a dielectric resonator in which a TM dual mode dielectric resonator 1 is provided in a cavity composed of a cavity frame 2 and side plates (not shown). The container is housed in a case composed of the case lower plate 3 and the case body 10.

At the tip of the dielectric rod 7b of the frequency adjusting screw 7, a resin guide 7c such as Teflon having an outer diameter substantially equal to that of the frequency adjusting hole 1a of the dielectric resonator 1 is attached. This guide 7c is for suppressing the characteristic variation due to vibration, impact, etc. after the frequency adjusting screw 7 is adjusted and fixed.

In this embodiment, first, the cavity side bush 4 and the case side bush 5 are attached to the cavity frame body 2 of the dielectric resonator through the toothed washer 6 by screwing. After that, the case mounting portion provided at the lower portion of the case side bush 5 is inserted into the case lower plate 3 and screwed and tightened with the lock nut 9 to attach the dielectric resonator to the case lower plate 3.

That is, the mounting structure of the cavity frame 2 and the case lower plate 3 of the dielectric resonator according to this embodiment is as follows.
The structure is shown in an enlarged manner in FIG.

As shown in FIG. 2, the case side bush 5 of this embodiment has a double-screw structure made of Ag-plated metal, and a case mounting portion is provided at the bottom of the flange. Then, first, the toothed washer 6 is put on the flange of the case side bush 5, the upper part of the case side bush 5 is inserted into the through hole of the cavity frame 2, and the cavity side bush is clamped so as to sandwich the cavity frame 2. 4 and case side bush 5 are screwed together and tightened.

Next, the case mounting portion below the case side bush 5 is inserted into the through hole of the case lower plate 3 and tightened with the lock nut 9, so that the dielectric resonator is fixed to the case lower plate 3.

A characteristic adjusting screw such as the frequency adjusting screw 7 or the coupling adjusting screw 8 is screwed into a screw hole on the inner peripheral surface of the case side bush 5, and is tightened with a nut 11 after adjusting the frequency and the coupling. It is fixed. The case lower plate 3 and the case body 10 are made of metal such as stainless steel, aluminum, copper alloy, and iron.

The other structure is the same as that shown in FIG. 4 of the conventional example, and the description thereof is omitted.

As described above, in the present embodiment, the case side bush in which the frequency adjusting screw or the like is inserted and the dielectric resonator is attached to the case lower plate has the threaded portion only on one side of the conventional flange. The feature is that the flange has been changed to one having threaded portions on both sides.

In this structure, the current flowing through the conductor on the outer surface of the Ag-plated toothed washer on the outer surface of the Ag-plated dielectric resonator, that is, on the outer surface of the cavity frame is the toothed washer and the Ag-plated case side bush. Since it flows through the surface of the flange, almost no current flows on the surface of the case lower plate having low conductivity and large conductor loss, and the insertion loss of this dielectric filter is greatly improved. With the structure of the present embodiment, for example, in a 900-MHz band TM mode duplexer having a six-stage configuration, it has been confirmed that the insertion loss is improved by about 0.2 dB as compared with the conventional example.

Further, after the case side bush is attached to the resonator single body, the case side bushed resonator single body can be attached to the case lower plate, and the workability thereof can be greatly improved.

Further, since the case lower plate is attached below the flange of the case side bush, the influence of the dimensional fluctuation of the case lower plate on the vertical fluctuation of the frequency adjusting screw etc. due to temperature change is reduced, and the filter of the frequency etc. is reduced. The temperature characteristic of the characteristic is improved.

In the above-mentioned embodiment, the dielectric resonator incorporating the cross-shaped TM dual mode dielectric resonator integrally molded with the cavity frame is described as an example, but the invention is not limited to this. It may have one columnar dielectric resonator or a plurality of dielectric resonators. Further, the dielectric resonator is not limited to the one integrally molded with the frame body, and the dielectric resonator may be baked and bonded to the cavity frame body with Ag paste or the like. Further, the cavity frame body may also be formed by baking and pasting four ceramic plates with Ag paste or the like. Also, the usage mode is not limited to the TM mode.

Further, in the above embodiment, the structure in which the case side bush is screwed into the screw on the inner peripheral surface of the cavity side bush has been described, but the present invention is not limited to this, and the cavity is formed on the inner peripheral surface of the case side bush. A structure in which the side bushes are screwed together may be used. In this case, the cavity side bush has a double screw structure, and the characteristic adjusting screw is screwed into the screw hole inside the cavity side bush.

Further, in the conventional example and the present embodiment, description has been made with the state diagram in which one dielectric resonator having a two-stage structure is attached to the lower plate of the case, but normally, a plurality of dielectric resonators are provided in the case. A high-performance dielectric filter with a multi-stage structure is constructed by mounting.

[0031]

As described above, according to the dielectric filter of the present invention, the current flowing on the surface of the cavity of the resonator hardly flows on the surface of the metal case having a large conductor loss, and the insertion loss is small. Can be greatly improved. Also, after attaching the case side bush to the resonator unit,
Since each of the case-side bushed resonators can be attached to the case lower plate, the workability of the attachment can be significantly improved, and the number of manufacturing steps can be reduced. Also,
It is possible to reduce the influence of the dimensional variation of the case lower plate due to the temperature change on the characteristic adjusting screw such as the frequency adjusting screw and improve the temperature characteristic.

Therefore, according to the present invention, it is possible to reduce the manufacturing cost, obtain an inexpensive high quality dielectric filter having a small insertion loss and good temperature characteristics.

[Brief description of drawings]

FIG. 1 is a side view showing a structure of a dielectric filter according to an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of a main part (bushing part) of FIG.

FIG. 3 is a side view showing the structure of a conventional dielectric filter.

4 is a partially enlarged sectional view of a main part (bushing part) of FIG.

[Explanation of symbols]

 1 Dielectric Resonator 1a Frequency Adjustment Hole 2 Cavity Frame 3 Case Lower Plate 4 Cavity Side Bush 5 Case Side Bush 6 Toothed Washer 7 Frequency Adjustment Screw 7a Screw Part 7b Dielectric Rod 7c Resin Guide 8 Coupling Adjustment Screw 9 Lock nut 10 Case body 11 Nut

Claims (2)

[Claims] 1. A cavity-side bush and a case-side bush in which a dielectric resonator having a dielectric resonator housed in a cavity is screwed onto one of the inner peripheral surfaces of the dielectric resonator and a characteristic adjusting screw is inserted. In a dielectric filter attached to a case using, a through hole is provided in a flat portion of the cavity and a predetermined position of the case, and the cavity of the dielectric resonator is inserted into the through hole of the cavity to form a cavity side bush. The case side bush was attached by screwing, and the dielectric resonator to which the case side bush was attached was inserted into the through hole of the case, the case attaching portion of the case side bush was tightened with a nut, and the case was attached to the case. A dielectric filter characterized by. 2. The dielectric filter according to claim 1, wherein a toothed washer is inserted between the cavity and the case side bush.