JP4030886B2 - Band pass filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bandpass filter, and more particularly to a bandpass filter including a rectangular waveguide and a conductor wall having an asymmetric structure.
[0002]
[Prior art]
Conventionally, a band-pass filter has been proposed in which an inductive window is formed by partitioning a rectangular waveguide with an appropriate length from its bottom surface to operate as a filter (see, for example, Patent Document 1).
[0003]
As shown in FIG. 4, in this band pass filter, a plurality of partition walls 32 forming an asymmetric inductive window 40 are integrally formed at a predetermined interval in a rectangular waveguide 39 having one side opening. 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. The 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 gazette
[Problems to be solved by the invention]
In the conventional bandpass filter, since the conductor walls are formed asymmetrically, an asymmetric electromagnetic field distribution is generated in the waveguide, and the resonance frequency is lowered when the insertion amount of the frequency adjusting screw 37 is increased. , The pass bandwidth is narrowed. Therefore, it is necessary to insert the coupling degree adjusting screw 38 in order to keep the passband width at a predetermined width. However, when the insertion amount 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 prominent as the insertion amount of the coupling degree adjusting screw 38 increases.
[0006]
In the conventional bandpass filter, the cutoff frequency of the higher-order mode depends on the dimension of the wide surface of the waveguide, and can be shifted to the high frequency side by reducing this. However, if the waveguide is made smaller, 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 conventional bandpass filter described above, and suppresses unnecessary spurious at a frequency lower than the resonance frequency of the TE ₂₀₁ mode, and without reducing the wide surface. An object of the present invention is to provide a band-pass filter capable of shifting the cutoff frequency to the high frequency side.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is a band-pass filter having a rectangular waveguide inside and extending from one inner wall to the inner wall opposite to the one inner wall, and is asymmetric inductive. 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 according to a length that is disposed at a position spaced from the partition wall and protrudes into the inductive window. A frequency adjusting screw and a coupling degree adjusting screw for adjusting the distance, and a diaphragm extending from the one inner wall between the adjacent partition walls are provided.
[0009]
According to the present invention, an unnecessary spurious response can be obtained by operating a diaphragm provided at one end of the filter unit in which the TE ₁₀₁ mode is hardly distributed to suppress 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 cut-off frequency can be shifted to the high frequency side without reducing the wide surface. .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
1 and 2 show an embodiment of a band-pass filter according to the present invention. This band-pass filter is roughly divided into a main body 11 made of a conductive material and a U-shaped waveguide having one side opened. A plurality of partition walls 12 partitioning the waveguide from the inner wall, a coupling degree adjusting screw 13 and a frequency adjusting screw 14 for adjusting the propagation frequency and the coupling degree of the waveguide by the length protruding into the main body 11, The cover 15 is made of a conductive material and is provided so as to block the opening side surface of the waveguide with respect to the main body 11, and the diaphragm 16 is provided between the adjacent partition walls 12.
[0012]
As in the conventional band-pass filter shown in FIG. 4, in the structure having a conductor wall asymmetric with respect to the waveguide, the asymmetry of the electromagnetic field increases as the coupling degree adjusting screw 38 is inserted . The electric field distribution constituting the TE ₂₀₁ mode generated in the −I line portion is as shown in FIG. Therefore, as in the band-pass filter according to the present invention shown in FIG. 1, by providing a diaphragm 16 at one end of the filter section 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]
As a result, the characteristics of the bandpass filter according to the present invention as shown in FIG. 3 can be obtained by shifting unnecessary spurious to the high frequency side from the characteristics 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 made smaller, but when the filter is formed at a high frequency where a small wide surface is required, the frequency adjusting screw 14 is used. And the coupling degree adjusting screw 13 can be prevented from physically interfering with each other, which is useful.
[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. It is possible to shift to the side.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing an embodiment of a bandpass filter according to the present invention.
FIG. 2 is a plan view of the band pass 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 bandpass filter.
FIG. 5 is a graph showing characteristics of the bandpass filter of FIG. 4;
6 is a cross-sectional view of the bandpass filter of FIG. 4 and a TE ₂₀₁ mode electric field distribution in a resonator of a certain phase.
[Explanation of symbols]
11 Main body 12 Partition wall 13 Coupling degree adjusting screw 14 Frequency adjusting screw 15 Cover 16 Aperture

Claims (1)

A rectangular waveguide having a rectangular waveguide therein and integrally formed with a plurality of partition walls extending from one inner wall to the inner wall opposite to the one inner wall to form an asymmetric inductive window When,
A frequency adjusting screw and a coupling degree adjusting screw, which are arranged at a position spaced from the partition wall and adjust the propagation frequency and the coupling degree of the waveguide according to a length protruding from the inductive window;
A band-pass filter comprising: a diaphragm extending from the one inner wall between the adjacent partition walls.

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