JP4143477B2 - 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. 3, 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 band pass filter, when the frequency is changed while maintaining a constant pass band, the frequency adjusting screw 37 and the coupling degree adjusting screw 38 are inserted, but the conductor walls are formed asymmetrically. There is a problem that an asymmetric electromagnetic field distribution is generated in the waveguide, and the TE ₂₀₁ mode is generated as a spurious of a higher order mode.
[0006]
Further, when the insertion amount of the frequency adjustment screw 37 is increased, the resonance frequency is lowered, but the passband width is also narrowed. In order to maintain the passband width, it is necessary to insert the coupling degree adjustment screw 38. When the insertion amount of the adjusting screws 37 and 38 is increased, a problem arises that a large number of spurious signals are generated at a frequency higher than the resonance frequency of the TE ₂₀₁ mode.
[0007]
Therefore, the present invention has been made in view of the problems in the conventional bandpass filter described above, and provides a bandpass filter that can suppress high-order mode spurious while maintaining a constant passband. For the purpose.
[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 a plurality of partition walls extending from one inner wall to form an asymmetric inductive window are integrally formed. The body is formed and the surface opposite to the inner wall is open, and the body is disposed at a position spaced from the partition wall, and the length protruding from the inductive window adjusts the propagation frequency and the degree of coupling of the waveguide. A frequency adjusting screw and a coupling degree adjusting screw; at least one columnar portion extending in parallel to the inner wall of the inductive window portion; and a cover for closing the open surface of the main body; The at least one columnar part is non-contact.
[0009]
According to the present invention, the inductive window is provided with at least one columnar portion extending in parallel to the inner wall, so that the pass bandwidth is adjusted while suppressing spurious in higher-order modes. Can do. In addition, since the columnar portion and the cover are not in contact with each other, manufacturing is facilitated.
[0010]
In the band pass filter, the columnar section may have a substantially circular cross section. As a result, the columnar part can be easily press-fitted into the main body, and the manufacture is further facilitated.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0012]
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, a partition wall 12, a coupling degree adjusting screw 13, and a frequency adjusting screw. 14, a cover 15, and a columnar portion 16.
[0013]
The main body 11 has a rectangular waveguide inside, and a plurality of partition walls 12 are integrally arranged on the inner wall to form an asymmetric inductive window. The surface facing the inner wall is open.
[0014]
The coupling degree adjusting screw 13 and the frequency adjusting screw 14 are arranged at positions separated from the partition wall 12 and adjust the propagation frequency and the coupling degree of the waveguide by the length protruding to the inductive window.
[0015]
In the embodiment shown in FIGS. 1 and 2, two columnar portions 16 are arranged in parallel to the inner wall formed integrally with the partition wall 12 of the main body 11 in the inductive window portion. It is necessary to provide at least one. Further, the cross section of the columnar portion 16 has a circular cross section so that it can be easily press-fitted into the main body 11, and is formed into a columnar shape as a whole. Any shape can be used as long as it does not hinder reflection.
[0016]
The cover 15 is provided to close the open surface of the main body 11, and the cover 15 is not in contact with the columnar portion 16.
[0017]
As described above, by providing the columnar portion 16 in the inductive window portion, in the case of the asymmetric bandpass filter, the TE ₂₀₁ mode generated by the configuration of the rectangular resonator sandwiched between the inductive window and the partition wall 12 is achieved. Cannot be propagated, and spurious in the higher mode is suppressed.
[0018]
Further, by providing the columnar portion 16 in the inductive window portion, the electromagnetic field distribution in the inductive window does not occur between the columnar portion 16 and the cover 15 which are extremely short compared to the guide mode wavelength in the fundamental mode. The same characteristics as those of the symmetric bandpass filter can be obtained.
[0019]
Further, in the configuration having the main body 11 and the cover 15 as in the present invention, it is conventionally necessary to bring the partition wall 12 and the cover 15 into contact with each other, and it has been difficult to realize a symmetric bandpass filter. Since the columnar portion 16 according to the present invention does not need to contact the cover 15, it can be easily designed and manufactured without considering the contact of the cover 15.
[0020]
FIG. 4 is a graph comparing filter characteristics between the structure described in Patent Document 1 as a conventional example (no columnar part) and the structure according to the present invention (two columnar parts). As can be seen from the figure, the configuration according to the present invention suppresses the spurious by the columnar portion 16 in the higher-order mode while maintaining the characteristics as the same band pass filter.
[0021]
In addition, the columnar part 16 can change a diameter and a number according to the level of the spurious to suppress. In addition, the position where the columnar portion 16 is installed increases the effect of suppressing higher-order modes as it approaches the center of the resonator.
[0022]
【The invention's effect】
As described above, according to the bandpass filter of the present invention, it is possible to provide a bandpass filter that can suppress high-order mode spurious while maintaining a constant passband and that is easy to manufacture. It becomes possible.
[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 an exploded perspective view showing an example of a conventional band-pass filter.
FIG. 4 is a graph comparing the characteristics of a bandpass filter according to the present invention and a conventional bandpass filter.
[Explanation of symbols]
11 Main body 12 Partition wall 13 Coupling degree adjusting screw 14 Frequency adjusting screw 15 Cover 16 Columnar part

Claims (2)

A main body having a rectangular waveguide inside, a plurality of partition walls extending from one inner wall to form an asymmetric inductive window, and a surface facing the inner wall being open;
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;
At least one columnar portion extending in parallel to the inner wall of the inductive window;
A cover for closing the open surface of the main body,
The bandpass filter, wherein the cover and the at least one columnar part are not in contact with each other. The bandpass filter according to claim 1, wherein a cross section of the columnar portion is substantially circular.

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