JPS59185402A - Waffle iron type filter - Google Patents

Abstract

PURPOSE:To put resonance due to a wave in high-order mode out of an in-use band almost without exerting influence upon the passing characteristics of a basic mode wave by making bosses uneven in height. CONSTITUTION:Bosses 3 which are high enough for necessary filter characteristics are provided near the center of a rectangular waveguide 1 and bosses 4 which differ in height from the bosses 3 are provided near narrow-width surfaces of the rectangular wave-guide 1. The electric field of the basic mode wave is small at the bosses 4, which, therefore, exert almost no influence upon the passing characteristics of the filter. The electric field of the high-order mode wave, however, is larger at the bosses 4 than the electric field of the basis mode wave, so the rate of wavelength shortening increases and the resonance frequency of the high-order mode wave varies greatly. Therefore, unnecessary resonance by the high-order mode wave is put out of the in-use resonance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Watsuful iron wave filter in which a plurality of bosses are provided on the inner wall of the wide side of a rectangular waveguide.

First, the conventional Watsuful iron filter shown in FIG. 1 will be briefly explained. FIG. 1(a) is a partially cutaway perspective view of a Watsuful iron filter, and FIG. 1(b) is a front view. In the figure, (1) is a rectangular waveguide, and (2) is a rectangular waveguide (
This is a boss with the same height as the cross-sectional shape provided on the inner wall of the wide surface of 1).

In the Watsuful iron filter having such a structure, the wavelength is shortened by the effect of the boss (2), so the cutoff wave number is lowered, and higher-order mode waves can propagate.

Therefore, the boss (2) lacks precision when manufacturing the filter.

When left-right asymmetry occurs, higher-order mode waves are generated and propagated. This higher-order mode wave is blocked and reflected by the waveguides connected to both ends of the filter, causing confined resonance at a frequency determined by the shape of the boss (2) and the axial length of the filter.

Conventional Watsuful iron filters have the disadvantage that when this confined resonance occurs within the passband, the resonant frequency cannot be moved outside the passband without changing the characteristics of the filter.

In order to eliminate these drawbacks, the present invention makes the height of the boss non-uniform, and will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, in which FIG. 2(a) is a partially cutaway perspective view and FIG. 2(b) is a front view. (1) in the diagram
is a rectangular waveguide, (3) is a boss with a height that provides the necessary filtering characteristics, and (4) is a boss with a different height from boss (3).

The boss (3) is located near the center of the rectangular waveguide (1).
) is provided close to the narrow surface of the rectangular waveguide (1).

Since the electric field of the fundamental mode wave is small at the position of the boss (4), the boss (4) has little effect on the passage characteristics of the filter. However, since the electric field of the higher-order mode wave is thicker than the electric field of the fundamental mode wave at the position of the boss (4), the wavelength shortening rate increases, and the resonant frequency of the higher-order mode wave changes significantly. Therefore, unnecessary resonance due to higher-order mode waves can be removed from the usable band.

This has the advantage of providing good transmission characteristics.

FIG. 3 shows another embodiment of the present invention, in which FIG. 3(a) is a partially cutaway perspective view and FIG. 3(b) is a front view. In the figure (1
) to (4) are the same as in FIG.

Only four bosses (4) are provided at positions close to the narrow side of the rectangular waveguide (1).

In this case, the boss (4) acts as a lumped constant capacitance for the higher-order mode waves, changing the resonance frequency of the higher-order mode waves. Therefore, although it has the same advantages as the case in FIG. 2, the change in the resonance frequency is smaller in the case in FIG. 3 than in the case in FIG. 2, so it is effective in finely adjusting the frequency of confined resonance.

Note that although the case in which a prismatic boss is used has been described in 9 and above, the present invention is not limited to this and may be used in a case where a cylindrical boss is used.

As described above, in the Watsuful iron filter according to the present invention, by making the height of the bosses non-uniform, resonance by higher-order mode waves is used with almost no effect on the passage characteristics of fundamental mode waves. It has the advantage of being able to go out of band.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a conventional Watsuful iron filter, in which Fig. 1(a) is a partially cutaway perspective view, Fig. 2(b) is a front view, and Fig. 2 is an embodiment of the present invention. FIG. 3A is a partially cutaway perspective view, and FIG. 1B is a front view. FIG. 3 is a diagram showing another embodiment of the present invention, in which FIG. 3(a) is a partially cutaway perspective view and FIG. 3(b) is a front view. In the figure, (1) is a rectangular waveguide, (2) is a boss with the same cross-sectional shape and height, (3) is a boss with a height that provides the necessary filtering characteristics, and (4) is boss (3). are bosses of different heights. In FIG. 9, the same or corresponding parts are designated by the same reference numerals. Agent Masuo Oiwa Figure 1 CI:)) Figure 2 rb) Figure 3 (b)

Claims (1)

[Claims] A Watsuful iron filter in which a plurality of prismatic or cylindrical bosses are provided on the inner wall of a wide surface of a rectangular waveguide, characterized in that the heights of the bosses are uneven. vessel.