JPH05110304A - Image type tm01delta mode dielectric filter - Google Patents

Abstract

PURPOSE:To eliminate the spurious response of an undesired low frequency side by adopting the image type for the TM01delta mode dielectric filter. CONSTITUTION:The image type TM01delta mode resonator is formed by making one flat end of a dielectric resonator 11 in contact onto a flat conductive plate so that one flat end of the round rod or cylindrical dielectric resonator 11 in the band pass filter comprising at least the one round rod or cylindrical dielectric resonator 11. Moreover, the conductive plate is preferably a metallic case 14 of the dielectric filter. In this case, the resonance mode having an electric field component in parallel with the conductive plate is suppressed by an electric resistance of the conductive plate, while the principle of the conductive plate giving no effect onto the mode in which the electric field is made vertically incident into the conductive plate is utilized. Thus, the spurious radiation whose frequency is lower than a frequency of the pass band of the desired TM01delta mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave band dielectric bandpass filter used in radio equipment and the like, and more particularly to a filter having improved insertion loss and spurious characteristics.

[0002]

2. Description of the Related Art In a filter using a dielectric resonator, a characteristic of the TM01δ mode is that a low-loss filter can be constructed because it has a higher no-load Q value than the most commonly used TE01δ mode.

A conventional example of a dielectric bandpass filter using such a TM01δ mode dielectric resonator is shown in FIG. 5 in plan view and in FIG. 6 in a cross section taken along line 6-6 in FIG.

As is clear from FIGS. 5 and 6, this filter has a metal case 38, and an input side connector 34 and an output side connector 3 attached to both ends of the metal case 38.
5, semi-rigid cables 36 and 37 connected to these connectors and protruding into the metal case, an input side probe 42 and an output side probe 43 connected to the tip of the cable, and at least one support in the metal case. At least one dielectric resonator (three dielectric resonators 31, 32, 33 in this conventional example) supported by a table (three support tables 39, 40, 41 in this conventional example). ..

Next, the operation will be described. The high frequency power input from the input side connector 34 is the input side probe 42.
To the first dielectric resonator 31 via a magnetic field. This high frequency power is continuously transmitted to the second dielectric resonator 32 and further to the third dielectric resonator 33, and finally passes through the output side probe 43 and is output to the output side connector 35. It Therefore, TM01
A bandpass filter is configured to pass only the bandwidth determined by the coupling amount between the resonators at a frequency corresponding to the resonance frequency of the δ mode.

[0006]

In the filter using the TM01δ mode dielectric resonator, as shown in FIG. 7 showing the frequency characteristics, in addition to the desired pass band (12 GHz) corresponding to the TM01δ mode, An unnecessary pass band corresponding to the TE01δ mode is generated on the lower frequency side (9.2 GHz) than this pass band.

Generally, it is theoretically unavoidable that a filter using a dielectric resonator causes a spurious response at a frequency higher than a desired frequency. However, considering the application of the filter to a wireless device, generating a pass band, that is, a spurious response below a desired frequency is a major obstacle.

As described above, the conventional filter using the TM01δ mode has a drawback that a spurious response of the TE01δ mode is generated below the desired pass band.

Therefore, it is an object of the present invention to provide a TM01δ mode dielectric bandpass filter which does not produce a spurious response below the desired passband.

[0010]

In order to achieve the above-mentioned object, the present invention provides a band-pass filter constituted by at least one cylindrical or cylindrical dielectric resonator, which has a cylindrical or cylindrical shape. An image type TM01δ mode resonator is prepared by contacting one flat end of the dielectric resonator with a flat conductive plate so that the dielectric resonator is perpendicular to the conductive plate. An image type TM01 δ mode dielectric filter characterized by being formed is adopted.

In the above filter, the conductive plate is preferably a metal case of the dielectric filter.

[0012]

According to the present invention, in the image type TM01 δ mode dielectric filter, one flat end of the dielectric resonator is arranged so that the cylindrical or cylindrical dielectric resonator is perpendicular to the conductive plate. The resonance mode with the electric field component parallel to the conductive plate is suppressed by the electric resistance of the conductive plate by forming the image type TM01δ mode resonator by contacting the part with the flat conductive plate. On the other hand, it utilizes the principle that the conductive plate has no influence on the mode in which the electric field is vertically incident on the conductive plate.

This principle is applied to TE01δ mode and TM01δ mode.
Explaining with reference to FIG. 1 showing the distribution of the electric field and magnetic field of the mode, as shown in FIG. 1, in the TE01δ mode, the electric field component has only a component parallel to the plane of the end portion of the cylinder of the dielectric. Therefore, when a conductive plate, for example, a metal plate is brought into contact with the end of the dielectric cylinder, the electric field is greatly attenuated by the electric resistance of the surface of the metal plate. As a result, TE01
The δ mode will be greatly attenuated. On the other hand, TM01δ
Even if the mode is cut at the center section (II section) of the cylinder, and the metal plate is brought into contact with this cut surface, the electric field components are all vertically incident on the metal plate. Has no effect on. At this time, an image dielectric is formed on the metal plate, and the actual dielectric and the image dielectric are combined to form one dielectric resonator.

Therefore, the TE01δ mode, which is a spurious response on the frequency side lower than the pass band of the desired TM01δ mode, which has been a problem in the conventional dielectric filter using the TM01δ mode, can be effectively suppressed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described with reference to the drawings.

FIG. 2 is a plan view showing an embodiment of the image type TM01δ mode dielectric filter of the present invention.
3 is a cross-sectional view taken along line 3-3 of FIG. 2, and FIG. 4 is a graph showing frequency characteristics of the dielectric filter of this example.

The dielectric filter of the present invention is shown in FIGS.
2, a metal case 14, an input side connector 15 and an output side connector 16 attached to both ends of the metal case 14, and semi-rigid cables 17 and 18 connected to these connectors and projecting into the metal case. , The input side probe 12 and the output side probe 13 connected to the tip of the cable, and at least one dielectric resonator (three in this embodiment) supported in direct contact with a metal case, that is, a conductive plate. Dielectric resonator 11, 11, 11).

The operation of the dielectric filter thus constructed is the same as the operation of the conventional dielectric filter, so the details thereof will be omitted. The occurrence of spurious response on the side is suppressed.

[0019]

Experimental Example Next, an experimental example based on the embodiment of the present invention will be described. As the dielectric resonator 11, a ceramic having a relative permittivity of 30, a diameter of 8.8 mm and a thickness of 2 mm is used, and one flat end of the dielectric resonator 11 is baked with a thick film silver paste. It was fixed to the case 14 by soldering. A loop-shaped probe was used as the input side probe 12 and the output side probe 13 so that magnetic field coupling could be effectively performed. When frequency characteristics were measured using this dielectric filter, the frequency characteristics shown in FIG. 4 were obtained. As is clear from FIG. 4, no spurious response was observed on the low frequency side as compared with the conventional TM01δ mode dielectric filter.

[0020]

As described in detail above, the present invention is
By making the conventional TM01δ mode dielectric filter an image type, unnecessary spurious response on the low frequency side can be removed.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining the principle of the present invention.

FIG. 2 is a plan view of a dielectric filter according to an embodiment of the present invention.

3 is a cross-sectional view taken along line 3-3 of FIG.

FIG. 4 is a graph showing frequency characteristics obtained by the dielectric filter of the present invention.

FIG. 5 is a plan view of a conventional dielectric filter.

6 is a cross-sectional view taken along line 6-6 of FIG.

FIG. 7 is a graph showing frequency characteristics of a conventional dielectric filter.

[Explanation of symbols]

 11 Dielectric Resonator 12, 13 Probe 14 Metal Case 15, 16 Connector

Claims (2)

[Claims] 1. A bandpass filter comprising at least one cylindrical or cylindrical dielectric resonator, wherein the cylindrical or cylindrical dielectric resonator is perpendicular to a conductive plate. An image type TM01δ mode dielectric filter, wherein one flat end of the dielectric resonator is brought into contact with a flat conductive plate to form an image type TM01δ mode resonator. 2. The image type TM01δ mode dielectric filter according to claim 1, wherein the conductive plate is a metal case of the dielectric filter.