JP2004235731A - Band-pass filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a band-pass filter which restricts unwanted spurious at lower frequencies than a resonance frequency of the TE<SB>201</SB>mode and shifts its cut off frequency to a higher frequency without reducing the broadside surface. <P>SOLUTION: The band-pass filter comprises a rectangular waveguide having a rectangular waveguide way inside and a plurality of partitions 12 extending from one inner wall to the opposite inner wall to form asynchronous inductive windows in one body, frequency and coupling adjusting screws 14, 13 positioned apart from the partitions 12 for adjusting the propagating frequency of the waveguide way and the degree of coupling according to their lengths projecting into the inductive windows, and irises 16 extending from the one inner wall between the adjacent partitions 12. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bandpass filter, and more particularly, to a bandpass filter including a rectangular waveguide and an asymmetric conductor wall.
[0002]
[Prior art]
Conventionally, a bandpass filter has been proposed in which an inductive window is formed by partitioning a rectangular waveguide from a bottom surface of the rectangular waveguide at an appropriate length to operate as a filter (for example, see Patent Document 1).
[0003]
In this band-pass filter, as shown in FIG. 4, a plurality of partition walls 32 forming an asymmetric inductive window 40 are integrally formed at predetermined intervals in a rectangular waveguide 39 having an opening on one side in accordance with a band frequency. And a cover 35 joined so as to close the opening surface of the rectangular waveguide 39, and a frequency adjusting screw 37 for adjusting the propagation frequency of the rectangular waveguide 39 is provided at an intermediate position between the partition walls 32. And a coupling degree adjusting screw 38 for adjusting the coupling degree is provided from the cover 35 toward the partition wall 32.
[0004]
[Patent Document 1]
Japanese Patent No. 3025930
[Problems to be solved by the invention]
In the above-mentioned conventional band-pass filter, since the conductor wall is formed asymmetrically, an asymmetrical electromagnetic field distribution occurs in the waveguide, and when the insertion amount of the frequency adjusting screw 37 is increased, the resonance frequency decreases. , The passband becomes narrower. Therefore, it is necessary to insert a coupling degree adjusting screw 38 in order to maintain the pass band width at a predetermined width. However, when the amount of insertion of the adjusting screws 37 and 38 is increased, there is a problem that spurious (unnecessary resonance) occurs at a frequency lower than the resonance frequency of the TE ₂₀₁ mode. This phenomenon becomes more remarkable as the insertion amount of the coupling degree adjusting screw 38 increases.
[0006]
Further, in the above-mentioned conventional band-pass filter, the cutoff frequency of the higher-order mode depends on the dimension of the wide surface of the waveguide. However, if the waveguide is reduced in size, there is a problem that the frequency adjusting screw 37 and the coupling degree adjusting screw 38 physically interfere with each other.
[0007]
Therefore, the present invention has been made in view of the problems in the above-described conventional band-pass filter, and suppresses unnecessary spurious at a frequency lower than the resonance frequency of the TE ₂₀₁ mode without reducing the wide surface. It is another object of the present invention to provide a bandpass filter capable of shifting a cutoff frequency to a higher frequency side.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a band-pass filter having a rectangular waveguide therein, and extending from one inner wall to an inner wall facing the one inner wall to form an asymmetric inductive filter. A rectangular waveguide in which a plurality of partition walls forming a window are integrally formed, and a propagation frequency and a coupling degree of the waveguide, which are arranged at positions separated from the partition wall and protrude into the inductive window. And a diaphragm extending from the one inner wall between the adjacent partition walls.
[0009]
According to the present invention, an unnecessary spurious response can be achieved by using a diaphragm provided at one end of the filter portion where the TE ₁₀₁ mode is hardly distributed to suppress the asymmetry of the electric field distribution with respect to the TE ₂₀ mode. Can be moved to the high frequency side, unnecessary spurious at a frequency lower than the resonance frequency of the TE ₂₀₁ mode can be suppressed, and the cutoff frequency can be shifted to the high frequency side without reducing the wide surface. .
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
FIGS. 1 and 2 show an embodiment of a band-pass filter according to the present invention. The band-pass filter is roughly divided into a main body 11 made of a conductive material and a U-shaped waveguide having an open side. Are formed, a plurality of partition walls 12 for partitioning the waveguide from the inner wall, a coupling degree adjusting screw 13 and a frequency adjusting screw 14 for adjusting a propagation frequency and a coupling degree of the waveguide by a length protruding into the main body 11, It is composed of a cover 15 made of a conductive material and provided so as to cover the opening side surface of the waveguide with respect to the main body 11, and a stop 16 provided between adjacent partition walls 12.
[0012]
In a structure having a conductor wall that is asymmetric with respect to the waveguide as in the conventional band-pass filter shown in FIG. 4, the asymmetry of the electromagnetic field increases as the coupling degree adjusting screw 38 is inserted, and the TE ₂₀₁ mode is reduced. The constituent electric field distribution is as shown in FIG. Therefore, as in the band pass filter according to the present invention shown in FIG. 1, by providing the diaphragm 16 at one end of a filter portion where the TE ₁₀₁ mode is hardly distributed, the electric field distribution is asymmetric with respect to the TE ₂₀ mode. Work to suppress.
[0013]
This makes it possible to obtain the characteristic of the bandpass filter according to the present invention as shown in FIG. 3 in which unnecessary spurious is shifted to the high frequency side from the characteristic of the conventional bandpass filter as shown in FIG. This characteristic is similar to the phenomenon seen when the wide surface of the waveguide is reduced, but when a filter is formed at a high frequency where a small wide surface is required, the frequency adjusting screw 14 is used. It is useful that physical interference between the screw and the coupling degree adjusting screw 13 can be avoided.
[0014]
【The invention's effect】
As described above, according to the bandpass filter of the present invention, unnecessary spurious at a frequency lower than the resonance frequency of the TE ₂₀₁ mode can be suppressed, and the cutoff frequency can be increased without reducing the wide surface. Side.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing one embodiment of a bandpass filter according to the present invention.
FIG. 2 is a plan view of the bandpass filter of FIG.
FIG. 3 is a graph showing characteristics of the bandpass filter of FIG. 1;
FIG. 4 is an exploded perspective view showing an example of a conventional band-pass filter.
FIG. 5 is a graph showing characteristics of the bandpass filter of FIG.
6 is a cross-sectional view of the bandpass filter of FIG. 4 and a diagram showing a TE ₂₀₁ mode electric field distribution in a resonator having a certain phase.
[Explanation of symbols]
11 Body 12 Partition wall 13 Coupling degree adjustment screw 14 Frequency adjustment screw 15 Cover 16 Aperture

Claims (1)

A rectangular waveguide having a rectangular waveguide inside, and integrally formed with a plurality of partition walls extending from one inner wall to an inner wall facing the one inner wall to form an asymmetric inductive window When,
A frequency adjustment screw and a coupling degree adjustment screw that are arranged at a position separated from the partition wall and adjust a propagation frequency and a coupling degree of the waveguide by a length protruding into the inductive window,
A band-pass filter provided between the adjacent partition walls and a stop extending from the one inner wall.

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