JPH0244901A - Waveguide low pass filter - Google Patents

Abstract

PURPOSE:To obtain a small sized light weight waveguide low pass filter by assembling a function blocking a harmonic wave and a function taking impedance matching to two flanges of a standard waveguide. CONSTITUTION:Waveguide 1, 5 are standard waveguides whose dimensions in E and H planes are identical and have a flange 2, a resonance window 3 with a block filter and a flange 4 with a resonance window respectively and a microwave in the TE10 mode being the basic mode at the fundamental frequency and the 2nd harmonic wave with respect to the fundamental frequency are inputted from the waveguide 1. An E plane size 8 being narrower than an E plane size 7 being the standard size of the waveguide 1 is given in a resonance window 3 of the flange 2 with a block filter so as to suppress the production of the harmonic mode with respect to the 2nd harmonic wave. Since the flange 4 with resonance window and the flange 2 with a block filter are connected together to realize the impedance matching at the fundamental frequency and the blocking of harmonic waves in this way, the weight and number of joints are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waveguide low-pass filter used for microwaves and millimeter waves.

[Conventional technology]

Conventional waveguide low-pass filters reduce the dimension of the waveguide in the E-plane direction in order to block the propagation of, for example, the 2nd and 3rd harmonics in the fundamental frequency transmission band of microwaves and millimeter waves. Then, the dimension of the E surface is periodically changed in this part to form the second. A waveguide low-pass filter is known that blocks the third harmonic and uses a frequency region lower than the third harmonic as a fundamental frequency pass region. For example, see Electronic Communication Handbook, edited by the Institute of Electronics and Communication Engineers, p. 755, Ohmsha (1978).

On the other hand, the input/output waveguides connected before and after this low-pass filter are generally constructed of standard waveguides (for example, waveguides with a ratio of H-plane dimensions to E-plane dimensions of 2:1). It is true. However, when the low-pass filter and the input/output waveguide of the standard waveguide are directly connected, an impedance mismatch occurs. The structure had a waveguide for impedance conversion to achieve impedance matching. Therefore, many waveguide circuits, including waveguides for impedance conversion, have been connected by flanges.

[Problem to be solved by the invention]

The conventional waveguide low-pass filter described above includes a low-pass filter section and an impedance conversion section for impedance matching between the input and output waveguides connected to the low-pass filter section. The overall length of the filter becomes longer by the dimension of the impedance converter, and it has to be connected with a large number of flanges, which has the disadvantage that the weight of each connection point increases.

An object of the present invention is to provide a small and lightweight waveguide low-pass filter that incorporates a harmonic blocking function and an impedance matching function into two flanges of a standard waveguide. It is in.

[Means to solve the problem]

The waveguide low-pass filter of the present invention has resonance windows with shortened E-plane and H-plane dimensions on each of the first and second flanges that connect two waveguides that propagate the fundamental mode. A recess in the E-plane direction located between the two resonance windows is provided in the first or second flange.

〔Example〕

Next, one embodiment of the present invention will be described with reference to the drawings. 1st
FIG. 2 is a front view of two flanges constituting an embodiment of the present invention, as viewed from the flange surfaces of two waveguides. 3(a) and 3(b) are cross-sectional views of this embodiment, and FIG. 3(a) is an AA vertical cross-sectional view (cross-sectional view of plane E) of FIGS. 1 and 2, and FIG. (1)
) shows a BB cross-sectional view (H-plane cross-sectional view) of FIGS. 1 and 2, and both drawings show a state in which two waveguides are connected.

The waveguide 1 and the waveguide 5 are standard waveguides with the same E-plane dimensions and H-plane dimensions, and each has flanges 2 and 3 with blocking filters and a resonant window I' flange 4. . waveguide 1
TE and o mode microwaves having fundamental frequencies of fundamental frequencies 1 to 1 and, for example, second harmonics of the fundamental frequencies are input. First, the resonant window 3 of the blocking filter efficiency 2 shown in FIG. It suppresses the generation of higher-order motes. This discontinuity between the H-plane dimension 7 and the H-plane dimension 8 results in isometric capacitive susceptance, and in order to cancel this, an inductive part 8 having an inductive susceptance as shown in FIG. 3(b) is formed. impedance matching is achieved. Furthermore, with the resonant window flange 4 connected to the back surface of the resonant window 3, recesses are formed on the E and H surfaces to reflect the second harmonic. The dimensions of this recess are determined while measuring the attenuation characteristics of the second harmonic, which will be described later.

Further, the resonant window 6 of the resonant window flange 4 is the resonant window 3 described above.
It has similar features and dimensions. In this way, the flange 2 with a blocking filter and the flange 4 with a resonance window are connected, and harmonic blocking and impedance matching for the fundamental wave are realized. For example, as shown in the characteristic diagrams in Figure 4 (a) and (b), the second harmonic of 23.6 GHz is attenuated, and the fundamental wave of 11.8 GHz has low loss. A waveguide low-pass filter having the following characteristics is obtained.

〔Effect of the invention〕

As explained above, according to the present invention, since the waveguide low-pass filter is incorporated into the waveguide flange, its weight and connection points are significantly reduced. Furthermore, since the waveguide low-pass filter is divided into two flanges, it has the advantage of being easy to manufacture and process.

[Brief explanation of the drawing]

Figures 1 and 2 are front views of one embodiment of the present invention, and Figure 3 (
4(a) and 4(b) are a longitudinal cross-sectional view and a cross-sectional view, respectively, of this embodiment, and FIGS. 4(a) and 4(b) are characteristic diagrams of this embodiment. 1.5...Waveguide, 2...Flange with blocking filter, 3.6...Resonance window, 4...Flange with resonance window, 7,
8...H surface dimension, 9...Guidance part.

Claims (1)

[Claims] A resonance window with shortened E-plane and H-plane dimensions is provided on each of the first and second flanges that connect two waveguides that propagate the fundamental mode, and an E-plane located between the two resonance windows is provided. A waveguide low-pass filter characterized in that a recess in the direction is provided in the first or second flange.