JPS626501A - Dielectric filter - Google Patents

Abstract

PURPOSE:To eliminate the undesired resonance mode by providing a conductive film to the surface of each dielectric resonance element provided in parallel in a cut-off waveguide in a direction perpendicular to the electric field of the basic mode. CONSTITUTION:The dielectric resonance element 1 is fixed perpendicularly to a guide wall of the cut-off waveguide 7 and elements 1 are provided in parallel in the cut-off waveguide 7 at a prescribed pitch. A conductive film 10 is formed to the end face of each dielectric resonance element 1 in a direction perpendicularly to the electric field 4. Thus, the effect on the basic mode is not given due to the loss of the electric field component in parallel with the conductive film 10 or attenuation and only the undesired resonance mode is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] By providing a conductive film in a predetermined direction on the surface of each parallel dielectric resonant element, unnecessary resonance modes of the dielectric filter are removed.

[Industrial application field]

The present invention relates to improvements in dielectric filters.

Various band-pass filters are available for microwave and millimeter wave bands, but dielectric filters are widely used because they have the advantage of being able to make the resonant part smaller than waveguide filters. has been done.

FIG. 3 is a perspective view of a dielectric resonant element constituting the dielectric filter. Reference numeral 1 shown in the figure is a cylindrical dielectric resonant element made of a dielectric material with a sufficiently large dielectric constant (for example, barium titanate). is set up.

The fundamental mode of such a dielectric resonant element 1 is T0IE
The electromagnetic field is called a mode, and the electromagnetic field consists of a concentric electric field 4 in a cross section perpendicular to the axis of the dielectric resonant element l, and a closed magnetic field 3 that penetrates the axis and returns parallel to the axis on the outside of the cylinder. It is.

The dielectric resonant element 1 installed within the cut-off waveguide confines the electromagnetic field inside and in the vicinity of the dielectric resonant element 1 in this way, and thus operates as a resonator.

Therefore, by arranging and coupling a desired number of such dielectric resonant elements 1 in a cut-off waveguide, a desired bandpass type dielectric filter can be obtained.

At this time, there is a strong demand for a dielectric filter that eliminates unnecessary resonance modes, has large out-of-band attenuation, and has a simple structure.

[Conventional technology]

FIG. 4 is a partially cutaway perspective view of a conventional dielectric filter, in which a supporting base 6 having a dielectric constant smaller than that of the dielectric resonant element 1 is fixed to one end face of the dielectric resonant element 1. ).

The dielectric resonant elements 1 are fixed perpendicularly to the tube wall of the cut-off waveguide 7 via the support base 6, and are arranged in parallel within the cut-off waveguide 7 at a predetermined pitch.

Furthermore, an adjustment screw 8 for frequency adjustment or coupling degree adjustment is inserted perpendicularly to the tube wall at a predetermined location on the tube wall parallel to the tube wall on which the dielectric resonant element 1 is installed.

However, in the dielectric filter configured in this manner, in addition to the electric field 4 of the fundamental mode, there is an unnecessary resonance mode having a component perpendicular to the electric field 4. Therefore, conventionally, a conductor bar 9 of a desired length is provided in the tube between the dielectric resonant elements 1 in a direction perpendicular to the electric field 4 to eliminate this unnecessary resonance mode.

[Problems to be Solved by the Invention] However, in the dielectric filter of the above-mentioned conventional example, in addition to the frequency adjustment screws and the coupling degree adjustment screws arranged in parallel within the waveguide, conductor bars 9 of the same shape are arranged in parallel. is provided to remove unnecessary resonance modes, but the structure inside the cut-off waveguide is complicated and the cost is high.

[Means for solving problems]

In order to solve the above conventional problems, the present invention provides a conductive film or a resistive film on the surface of each dielectric resonant element 1 arranged in parallel in the cut-off waveguide 7 in a direction perpendicular to the electric field 4 of the fundamental mode. A conductive film such as the one described above is provided to eliminate unnecessary resonance modes.

[Effect]

According to the above means of the present invention, by providing the conductor film in a direction perpendicular to the electric field 4 of the fundamental mode, electric field components parallel to the conductor film cannot exist, unnecessary resonance modes are eliminated, and the resistance When a film is provided, electric field components parallel to the resistive film are attenuated and unnecessary resonance modes are eliminated.

Since the conductive film is provided on the surface of the dielectric resonant element 1 in this way, the structure inside the cutoff waveguide 7 is simple and the cost is low.

〔Example〕

The present invention will be specifically explained below with reference to illustrated examples. Note that the same reference numerals indicate the same objects throughout the figures.

FIG. 1 is a partially cutaway perspective view of one embodiment of the present invention.
(al and (bl) in FIG. 2 are perspective views of dielectric resonant elements of other embodiments, respectively.

In FIG. 1, dielectric resonant elements 1 are fixed perpendicularly to the tube wall of a cutoff waveguide 7 via a support 6, and are arranged in parallel within the cutoff waveguide 7 at a predetermined pitch.

Note that an adjustment screw 8 for frequency adjustment or coupling degree adjustment is inserted perpendicularly to the tube wall at a predetermined location on the tube wall parallel to the tube wall on which the dielectric resonant element 1 is installed.

A conductive film 10 is formed on the end face of each dielectric resonant element 1 in a direction perpendicular to the electric field 4, that is, in the diametrical direction in the figure.

This conductive film 10 is a conductor film or a resistive film,
It is formed by gluing foil-like materials or using thin film formation technology or thick film formation technology.

As mentioned above, by providing the conductive film 10 in the direction perpendicular to the electric field 4 of the fundamental mode, the electric field component parallel to the conductive film 10 is eliminated (or attenuated) and does not affect the fundamental mode. Only unnecessary resonance modes are removed without causing any damage.

If the conductive film is provided in a direction perpendicular to the electric field 4 of the fundamental mode, it will not affect the fundamental mode and will be effective in eliminating unnecessary resonance modes. It is not limited to one direction.

For example, as shown in FIG. 2(a), a plurality of conductive films 11 may be provided in the diametrical direction on the end face of the dielectric resonant element 1, and as shown in FIG. 2(b), the dielectric resonant element 1 may be A conductive film 12 may be provided on the circumferential surface of 1 parallel to the axis. Furthermore, it is of course possible to provide a combination of (a) and (b).

〔Effect of the invention〕

As explained above, the present invention provides a conductive film in the direction perpendicular to the electric field of the fundamental mode, which eliminates unnecessary resonance modes, and makes the structure inside the cutoff waveguide simple and low cost. , has excellent practical effects.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of one embodiment of the present invention, FIGS. 2(a) and 2(b) are perspective views of dielectric resonant elements of other embodiments, and FIG. 3 is a dielectric A perspective view of a dielectric resonant element constituting a filter. FIG. 4 is a partially cutaway perspective view of a conventional dielectric filter. In the figure, 1 is a dielectric resonant element, 2 is a conductor wall, 3 is a magnetic field, 4 is an electric field, 6 is a support base, 7 is a cutoff waveguide, 8 is an adjustment screw, 9 is a conductor bar, 10, 11. 12 indicates a conductive film. $Ig a) Me2 1ζriv5θ11's bji drama Mial Tazo (Rine) 4'2
Figure 4: 2000 smoke b

Claims (1)

[Claims] A dielectric filter characterized in that a conductive film is provided on the surface of each dielectric resonant element in a direction perpendicular to the electric field of the fundamental mode.