JP4873642B2 - Waveguide bandpass filter - Google Patents

Description

  The present invention belongs to the technical field of combined waveguide filters.

As a conventional waveguide bandpass filter, a bandpass characteristic is realized by providing a waveguide resonator in a direction in which electric field components are orthogonal to each other (for example, see Patent Document 1), or in a waveguide A dielectric window is provided at a plurality of locations in the transmission direction to realize bandpass characteristics (see, for example, Patent Document 2), or narrow wall surfaces on both sides of the waveguide from one H surface to the other H surface. In some cases, bandpass characteristics are realized by providing a plurality of protruding structures (inductive elements) extending in the tube axis direction (for example, see Patent Document 3).
JP 2004-274341 A (paragraphs [0014], [0020], [0023], FIG. 2, FIG. 5, FIG. 7) Japanese Patent No. 3602493 (paragraphs [0014] and [0017], FIGS. 1 and 2) JP-A-9-232813 (paragraphs [0011], [0012], FIG. 1 and FIG. 2)

  However, the invention described in Patent Document 1 cannot be used when the cavity resonator is provided in a direction orthogonal to the transmission direction, so that it increases in the height direction of the waveguide and there is only space in the transmission direction. There is a problem.

  In the invention described in Patent Document 2, when a plurality of inductive windows are provided in a waveguide (six in the embodiment at about half-wavelength intervals) and other cavity portions are provided, the size of the propagation direction of the entire filter is 3 wavelengths or more. There is a problem that it becomes long and does not become small.

  The invention described in Patent Document 3 also includes a plurality of inductive coupling means (in the embodiment, four places at half-wavelength intervals), and further, since the inclined portions at both ends require half-wavelengths, the number of wavelengths becomes two or more, and the size is not reduced. There is a problem.

  In view of the problems of the above-described conventional waveguide bandpass filter, the problem of the present invention is that the arrangement of elements in the transmission direction can be improved without providing a waveguide resonator or the like in a direction orthogonal to the transmission direction. It is to realize a small waveguide bandpass filter.

The present invention has the following means to solve the above problems.
In other words, the waffle structure filter having a low-pass filter characteristic has a small aperture having a high-pass filter characteristic having a high-pass band overlapping the low-pass band of the waffle filter on both sides in the transmission direction of the waffle filter. A waveguide bandpass filter.

The waffle structure filter is a low-pass filter (LPF). On the other hand, a filter having a small aperture structure is a high-pass filter (HPF).
In the configuration of the present invention, the low-pass band of the waffle filter and the high-pass band of the small aperture are overlapped so that the small apertures are provided on both sides in the transmission direction of the waffle structure filter. The band that overlaps becomes the passband, and transmission is attenuated by the attenuation characteristics of the waffle filter at higher frequencies, and transmission is attenuated by the attenuation characteristics of the small aperture at lower frequencies. Will be obtained.

As for dimensions in the tube axis direction, the waffle portion is approximately 0.135λ _g (λ _g : wavelength in the tube), one small aperture portion is 0.067λ _g , and the cavity resonance between the waffle portion and the small aperture And the matching part are 0.25λ _g , the input / output cavity resonance part between the small aperture and the external connection waveguide is 0.125λ _g , and the individual dimensions are small. There may be a small number that one is required before and after the waffle portion, and according to the above numerical value, the total length is about 1.02λ _g , 3λ _g or more in the example in Patent Document 2, Compared to the dimension of 2λ _g or more in the example in Document 3, there is an effect that a significant dimension reduction can be obtained.

  Furthermore, in addition to the bandpass characteristic, there is also a characteristic that it attenuates at the second and third harmonics of the passband frequency obtained from the waffle structure, and there is also an effect that it has both functions of bandpass and spurious suppression.

  In implementing the waveguide band-pass filter of the present invention, the normal waveguide portion may be connected to both ends of the filter so that a simple waveguide portion having a small length and an external connection waveguide can be easily connected. It is the best embodiment to provide the flanges.

  As a method for manufacturing such a waveguide filter, a waveguide band-pass filter according to the present invention is manufactured by die-casting a half shape obtained by cutting the waveguide band-pass filter at a half of the E-plane at a plane parallel to the H-plane. However, the best embodiment is to match the two into one filter.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view of a lower portion of a waveguide bandpass filter according to the present invention cut along a plane parallel to the H plane at a position half the E plane. Therefore, as a whole, the same structure is overlapped and integrated so as to match the cut surfaces.
When viewed in the transmission direction of the waveguide, the matching unit 7, the second cavity resonance unit 6, the small aperture unit 4, and the first cavity resonance unit sequentially and symmetrically toward the input side and the output side around the waffle unit 8. 5 is arranged, followed by the WRJ-10 waveguide 2, and a flange 3 for connection to the external waveguide is provided at the end thereof.

The waffle portion 8 has three prisms standing from an H-plane wall having a predetermined dimension in the tube axis direction. The top surface of the waffle portion 8 is opposed to the top surface of the prism from an upper H-surface wall (not shown), but with a predetermined gap. have. This waffle portion 8 has LPF characteristics.
Next, a matching portion 7 is provided. The matching portion 7 is a portion for matching the subsequent second cavity resonance portion 6 and the waffle portion 8.
The second cavity resonating unit 6 is provided in order to give a width of bandpass characteristics by resonating here.

Next, a small aperture portion 4 having HPF characteristics is provided.
The small aperture part 4 realizes both an inductive element and a capacitive element equivalently at one place in the transmission direction by narrowing the electromagnetic wave transmission path from the left and right E plane walls and from the upper and lower H plane walls. This is effective in shortening the dimension of the entire filter in the transmission direction.

Subsequently, the WRJ-10 waveguide 2 is formed through the first cavity resonator 5.
The first cavity resonating unit 5 is provided as a matching means for reducing reflection between the small aperture unit 4 and the WRJ-10 waveguide 2.
The WRJ-10 waveguide is a standard waveguide in the 8.20 to 12.4 GHz band, and is not an element for obtaining the frequency characteristics of the bandpass filter of the present invention, but is externally connected to the filter of the present invention. Since the WRJ-10 waveguide is used in this embodiment as the waveguide circuit, the WRJ-10 waveguide 2 with the flange 3 is formed integrally with the filter so that it can be easily connected to the waveguide circuit.
In addition, on the outside of the H surface of the alignment portion 7 and the small aperture portion 4, a lightening portion 9 for weight reduction is provided.

Figure 2 is a simulation calculation example of the curve of the reflection characteristic S ₁₁ and pass characteristic S ₂₁ of the present invention a waveguide bandpass filter in the case of a 9.410GHz the center frequency of the pass band.
Dashed line a passing characteristic _{S 21,} the solid line is a reflection characteristic _{S 11.}
Looking at the pass characteristics, it can be seen that attenuation is large in the vicinity of 18.8 GHz, which is twice the center frequency 9.410 GHz, and spurious suppression is effective for the second harmonic.

It is a perspective view of the lower part when the waveguide band pass filter of the present invention is cut by a plane parallel to the H plane at a half height position of the E plane. It is a curve simulation calculation example of reflection characteristic S ₁₁ and pass characteristic S ₂₁ of the present invention the waveguide band-pass filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waveguide band pass filter 2 WRJ-10 waveguide 3 Flange 4 Small aperture part 5 1st cavity resonance part 6 2nd cavity resonance part 7 Matching part 8 Waffle part 9 Thickening part

Claims (1)

  A waffle structure filter having a low-pass filter characteristic has a small aperture having a high-pass filter characteristic having a high-pass band overlapping with the low-pass band of the waffle filter on both sides in the transmission direction of the waffle filter. Wave tube bandpass filter.

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