JPH02190001A - Corrugate filter - Google Patents

Abstract

PURPOSE:To decrease number of stages and to suppress the impedance of a pass band and to improve the characteristic even when a band difference between the passing band and a block band by making the depth of plural corrugate grooves provided on a rectangular waveguide constant and changing the width periodically in the guide axis direction. CONSTITUTION:An impedance matching section 2 is formed respectively to both ends of rectangular waveguide land plural corrugate grooves 3 orthogonal to the guide axis are formed to a inner wall of an H plane of the waveguide while being arranged apart in the guide axis direction. The depth L of the corrugate groove 3 is made constant, while the width (d) of the corrugate groove is differentiated so as to be changed periodically in the guide axis direction. As a result, while the frequency in which the depth of the corrugate groove 3 is nearly lambdag/4 is fixed, the impedance in the frequency at the pass band is freely changed. Thus, the impedance distribution at the pass band is optimized such as Chebychev distribution with less number of stages and large attenuation is realized.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a corrugated filter.

[Conventional technology]

As an example of a conventional corrugated waveguide filter is shown in FIG. It has a configuration in which a plurality of corrugated grooves 13 are arranged in the direction. This corrugated groove 13 is shown in Fig. 4[・a]
As schematically shown in Figure 1, it has a simple rectangular shape, and its equivalent circuit around the fundamental wave is as shown in Figure 3(b).

In this case, the impedance Z of the single corrugated gate is given by the following equation.

Z = j Zo (A tanθ, +X) where,
Zo is the characteristic impedance of the main wave tube, A and X are coefficients determined by the main wave tube and corrugate shape, respectively, and θ1 is (2
π/λg)L+, L+ is the depth of the corrugated groove.

In this case, the depth of the corrugated groove is approximately (λg
/4). The impedance is infinite at (
0)) The frequency of the 0 pass band is fP + the frequency of the element band is f (rp<r*).If flI is set to f-, the amount of attenuation can be increased, but at the same time the impedance at f increases. , the passband characteristics deteriorate.

For this reason, we usually choose between f+*@fp and f, .
Attenuation was obtained by reducing the impedance at fp and stacking a large number of stages.

In addition, in order to further improve the characteristics of the passband, as shown in Fig. 3, the depth of the corrugated groove 13 is periodically changed to obtain an appropriate distribution in terms of impedance (for example, Tievisiev distribution). has also been devised.

[Problem to be solved by the invention]

The conventional wave filter described above requires a large number of stages in order to obtain the desired amount of attenuation, and when used in a polarization splitter, the stopband reflection surface is located near the center of the filter. There's a problem. Further, when the band difference between the pass band and the stop band is small, there is a problem that the impedance of the pass band becomes large and the characteristics deteriorate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a corrugated filter that can reduce the number of stages and improve characteristics by suppressing impedance in the pass band even when the band difference between the pass band and the stop band is small.

[Means to solve the problem]

The corrugated filter of the present invention has a constant depth of a plurality of Corday grooves formed on the inner wall of the H-plane of a rectangular waveguide,
The structure is such that the width dimension changes periodically in the tube axis direction.

[Effect]

In the above configuration, by periodically changing the width of the corrugated groove with a constant depth in the tube axis direction, the impedance at the frequency of the passband is kept small, while
It becomes possible to bring the frequency at which the impedance becomes infinite to the frequency of the stop band.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is an axial cross-sectional view showing one embodiment of a corrugated filter according to the present invention. This corrugated wave filter has impedance matching parts 2 formed at both ends of a rectangular waveguide 1, and impedance matching parts 2 formed in the middle part on the inner wall of the H plane of the waveguide part.
A plurality of corrugated grooves 3 orthogonal to the tube axis are formed so as to be spaced apart in the tube axis direction.

While the depth L of the corrugated grooves 3 is constant, the width dimension d of each corrugated groove is varied so that it changes periodically in the tube axis direction.

According to this configuration, the depth of the corrugated groove 3 is approximately (λg/
4) While fixing the frequency f, , the impedance at the passband frequency f can be freely changed, so while keeping the impedance at the passband frequency f small, the stopband frequency can be changed. f
, it becomes possible to realize a corrugated groove with infinite impedance. As a result, the stopband reflection surface is close to the input end, and the impedance distribution of the passband can be optimized, for example, like the Tievisiev distribution, with a small number of stages.
A corrugated filter with large attenuation can be realized.

Further, even when the band difference between the pass band and the stop band is small, the characteristics of this corrugated filter can be improved by appropriately selecting the parameters.

〔Effect of the invention〕

As explained above, in the present invention, the depth of the plurality of corrugated grooves provided in the rectangular waveguide is kept constant, and the width dimension is periodically changed in the tube axis direction, so that the impedance at the frequency of the passband is reduced. While keeping the impedance small, it is possible to bring the frequency at which the impedance becomes infinite close to the frequency of the stopband, and the stopband reflection surface is close to the input end (and the impedance distribution of the passband is optimized with a small number of stages). A corrugated filter with a significantly large attenuation can be obtained.Furthermore, the characteristics can be improved even when the band difference between the pass band and the stop band is small.

[Brief explanation of the drawing]

FIG. 1 is an axial sectional view showing an embodiment of a corrugated filter according to the present invention, FIG. 2 is an axial sectional view showing an example of a conventional corrugated filter, and FIG. 3 is an axial sectional view showing an example of a conventional corrugated filter. FIG. 4(a) is a schematic diagram of a corrugated groove, and FIG. 4(b) is an equivalent circuit diagram thereof. 1... Rectangular waveguide, 2... Impedance matching section,
3... Corrugated groove, 11... Rectangular waveguide, 12...
... Impedance matching part, 13... Corrugated groove. Figure 1 Figure 4 Figure 2 Figure 3

Claims (1)

[Claims] 1. In a corrugated filter in which a plurality of corrugated grooves perpendicular to the tube axis are arranged on the inner wall of the H-plane of a rectangular waveguide in the tube axis direction, the depth of the corrugated grooves is constant and the width dimension is A corrugated filter characterized by periodic changes in the axial direction.