JPS61135202A - Porous high-degree mode coupler - Google Patents

Abstract

PURPOSE:To eliminate the adverse effects of an undesired high-degree mode of transmission to an antenna radiation pattern, by setting a transmission frequency band-pass filter containing a radio wave absorber to the side face parallel to a magnetic field vector of a basic mode of a rectangular secondary waveguide. CONSTITUTION:The transmission wave 11 is transmitted through a primary waveguide 2 and also leaked out partly with connection of an electric field to a secondary rectangular waveguide 1 through a coupling hole 3. When no circular filter 4 is provided, the wave 11 transmitted through the waveguide 1 enters again the waveguide 2 via the hole 3 as shown by an arrow 13 and produces an undesired high-degree mode. Then a filter 4 is provided to the waveguide 1 so that the wave 11 passing through the waveguide 1 is connected to the filter 4 and absorbed by a radio wave absorber 5. This prevents the second transmission of the wave 11 to the waveguide 2. In such a way, the adverse effects of an undesired high-degree mode can be avoided to an antenna radiation pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is directed to a porous high-order mode which is used for information detection, etc., in which an antenna of an earth station tracks a satellite in microwave satellite communication. This invention relates to improving the suppression of unnecessary higher-order modes during transmission by a coupler.

(Prior art) A porous high-order mode coupler is composed of a main waveguide and a rectangular sub-waveguide, and the image forming part is electromagnetically coupled through a plurality of A-order coupling holes on the side surface of the main waveguide. Additionally, certain higher-order modes passing through the main waveguide are coupled to the rectangular sub-waveguide.

In satellite communications, a method for automatically tracking a satellite with an earth station antenna is to detect a specific high-order mode of electromagnetic waves generated within the circular waveguide of the antenna feed section when the earth station antenna deviates from the satellite direction. It is used as a signal for antenna direction control.

A porous high-order mode coupler is used to extract a specific high-order mode electromagnetic wave generated within the circular waveguide of the antenna feeding section. In other words, when the direction of the earth station antenna deviates from the satellite direction, the high-order mode electromagnetic waves generated in the circular waveguide of the antenna feed section are fed into the porous high-order mode by the received waves from the satellite. The antenna is coupled to the rectangular sub-waveguide of the antenna and taken out to obtain the signal necessary for automatic tracking of the earth station antenna, and the direction of the antenna is controlled so that it always faces the satellite.

In this refined satellite communication, the size, shape, and spacing of the coupling port of the porous high-order mode coupler are selected so that the degree of coupling is optimal for the high-order mode of the received wave.

However, even when the transmitted wave passes through this higher-order mode coupler, a part of it leaks into the sub-waveguide. Conventionally, a method of preventing this problem has been to install a metal blocking rod in the coupling hole to completely suppress the leakage of the transmitted wave to the sub-waveguide.

(Problem to be solved by the invention) Currently, the frequency bands used in satellite communications are being expanded due to the increasing demand for information, and development is progressing not only to lower frequencies but also to higher frequencies. It is being

When the frequency is extended to higher frequencies, the interval between the transmission frequency band and the reception frequency band may be narrower than the C band (4/soHg band), which is the main frequency band used in the past.

As mentioned above, as the frequency used increases, the metal blocking rod becomes smaller and becomes difficult to process and install, and as the frequency interval between the transmitting and receiving bands becomes smaller, it is necessary to design a metal blocking rod that is effective only in the transmitting frequency band. This makes it difficult to attach the metal blocking rod to the coupling hole. In a higher-order mode coupler having a coupling hole without a metal blocking rod, the transmitted radio wave naturally couples from the main waveguide to the sub waveguide via the coupling hole in the transmission band. The combined radio wave propagates through the sub-waveguide and enters the main waveguide again through the coupling hole, generating higher-order modes.This higher-order mode wave causes degradation of the antenna radiation pattern and is currently being used as an evaluation item for antenna characteristics. There is a problem if it causes a deterioration in orthogonal polarization discrimination, which is considered important.

(Tth Means for Solving the Problems) In consideration of the problems of the above-mentioned conventional porous high-order mode coupler, the present invention provides high-order waves generated by received waves from satellites that are necessary for controlling the antenna direction of the earth station. The coupling of the electromagnetic wave of the mode to the sub-waveguide and the propagation within the sub-waveguide are not affected, while the transmitted wave leaking from the main waveguide into the sub-waveguide is returned to the main waveguide. This method attempts to solve the problems of deterioration of the radiation pattern of the earth station antenna and deterioration of orthogonal polarization discrimination by using a gold film.

The present invention has the following configuration to achieve the above object. That is, in a porous higher-order mode coupler, one or several beams are placed on the side of the rectangular sub-waveguide parallel to the magnetic field vector of the fundamental mode (TE mode) propagating within the rectangular sub-waveguide. This is a second-order elongated hole-type higher-order mode coupler equipped with a transmission frequency band-pass filter with a radio wave absorber.

(Function) As described in the explanation of the solution, the porous higher-order mode coupler of the present invention has a radio wave absorber at the end of the rectangular sub-waveguide on the tube wall surface parallel to the magnetic field vector of the TE+ mode. A transmit frequency bandpass filter is installed. - Since the coupling hole is not provided with a metal blocking rod, the electromagnetic wave that leaks into the sub waveguide through the coupling hole among the transmitted radio waves propagating in the main waveguide propagates in the TE1m mode. However, since the sub-waveguide is equipped with a transmission frequency band-pass filter with a radio wave absorber attached to the end on the tube wall parallel to the magnetic field vector of the TB+ mode, the leaked electromagnetic waves of the TEn mode are at the transmission frequency. It passes through the bandpass filter and is absorbed by the radio wave absorber. Therefore, the electromagnetic waves that reenter the main waveguide from the sub-waveguide are almost negligible, and unnecessary higher-order mode waves are not generated, leading to antenna pattern deterioration and orthogonal polarization discrimination. The problem of deterioration disappears.

Some high-order mode electromagnetic waves due to waves received from the satellite enter the sub-waveguide through the coupling hole and propagate, but since their frequency is outside the passband of the transmission frequency band-pass filter, they are absorbed by the radio wave absorber. It propagates without any problem.

(Example) FIG. 1 shows a TE-1 mode coupler as an example of the porous higher-order mode coupler of the present invention. Figure (a) is a front view, and figure (b) is a right side perspective view. The higher-order mode coupler is electromagnetically coupled to the main waveguide 2 and the rectangular sub-waveguide 1 through a knot hole 3 .

A circular filter 4 is attached to the side surface of the rectangular sub-waveguide 1 parallel to the magnetic interface in the TE+- mode, and a radio wave absorber 5 is further provided at the tip thereof.

The circular filter 4 is a bandpass filter that passes electromagnetic waves in the transmission frequency band.

FIG. 2 shows a schematic diagram of a three-stage circular filter as an example.

The circular filter is composed of a circular waveguide 10 and a metal plate 9 which is perpendicular to the tube axis of the waveguide and has a circular opening 8 at its center. Here, the diameter of the circular waveguide, the length of the waveguide, the diameter of the hole in the metal plate, and the number of stages of the filter are determined by the frequency characteristics of the degree of radio wave coupling required of the filter.

In the figure, reference numeral 5 indicates a radio wave absorber, and a radio wave absorber consisting of 7 elements is attached to a circular waveguide.

FIG. 3 schematically shows the propagation of electromagnetic waves in the waveguide of the porous higher-order mode coupler of the present invention.

The transmitted wave 11 propagates through the main waveguide 2, but a part of it is electrically coupled to the sub waveguide 1 via the coupling hole 3 and leaks. In the absence of the filter 4, the transmitted wave 11 propagating through the sub-waveguide 1t reenters the main waveguide 2 from the coupling hole 3 as shown by the arrow 13, generating unnecessary higher-order modes.

Therefore, when the filter 4 is attached to the sub-waveguide 1, the transmitted wave 11 propagating through the sub-waveguide 1 is coupled with the filter 4,
It is absorbed by the radio wave absorber 5 and can be prevented from re-entering the main wave pipe 2.

At this time, the frequency characteristics of the degree of coupling of the filter (the ratio of electromagnetic energy absorbed by the filter to the electromagnetic energy propagating through the sub-waveguide) are as shown in Figure 4, and the coupling with the radio waves at the receiving frequency is as follows. is kept sufficiently low.

Ninth, from the main waveguide 2 to the sub waveguide 1 via the coupling hole 3.
High-order mode radio waves 12 of received waves that enter the interior and propagate therein
is not affected by filter 4 at all.

As described above, by providing a circular filter and a radio wave absorber in the sub-waveguide, the leakage radio waves from the transmitted radio waves to the sub-waveguide are absorbed without affecting the necessary received signals, and the radio waves are redirected to the main waveguide. By suppressing the intrusion, it is possible to prevent deterioration of the transmitting antenna pattern and deterioration of orthogonal polarization discrimination.

The present invention is not limited to the TE・1 mode coupler described above as an example, but also applies to porous higher-order mode couplers (for example, TEat, TM・1 mode coupler) composed of a main waveguide and a sub waveguide. This method is effective when the sub-waveguide is a rectangular waveguide in a field coupler, etc.), and the unnecessary transmission leakage radio waves that propagate in the middle range are in the TE or @ mode.

(Effects of the Invention) As explained above, the porous higher-order mode coupler of the present invention has one or more radio wave absorbers on the side surface parallel to the magnetic field vector of the TEL mode of the rectangular sub-waveguide. By providing a transmission frequency band-pass filter with an attached transmission frequency, even if a metal blocking rod is not provided in the coupling hole, the coupling and propagation of higher-order modes by received waves are not affected in any way, and the transmission frequency can be adjusted from the main waveguide to the sub-waveguide. The transmitted radio waves leaked to the pipe are absorbed by the radio wave absorber to prevent re-leakage to the main wave pipe, and the occurrence of unnecessary higher-order modes caused by re-leakage waves is completely suppressed.
Even in cases where it is difficult to install a metal blocking rod in the coupling hole due to the expansion of the frequency used in satellite communications to a high frequency of 10,000, it is possible to prevent the deterioration of the antenna radiation pattern and the deterioration of orthogonal polarization discrimination caused by higher-order modes that do not require transmission. The advantage is that it can be prevented from occurring.

[Brief explanation of the drawing]

Figure 1 shows TBu of the porous higher-order mode coupler of the present invention.
Figure 2 is a perspective view of a companion structure in which a circular filter with a radio wave absorber is attached to a rectangular sub-waveguide, and Figure 3 is a diagram showing the structure of an embodiment of a mode coupler. FIG. 4 is a diagram schematically showing the state of electromagnetic wave propagation, and is a diagram showing the frequency characteristics of the degree of coupling of the filter. 1... Rectangular sub-waveguide, 2... Main waveguide, 3... Coupling hole, 4... Circular filter, 5...・Radio wave absorber, 6...
・TE, mode electric field vector, 7...TE
I. Mode magnetic field vector, 8...Circular loop in metal plate 99...Metal plate, 10...Circular waveguide, 11...Transmission wave, 12...Received wave, 13...Promotion of the transmitted wave to the main waveguide

Claims (1)

[Claims] In a porous higher-order mode coupler, one or more radio wave absorbers are attached to the side surface of the rectangular sub-waveguide parallel to the magnetic field vector of the fundamental mode (TE_1_0 mode) propagating within the rectangular sub-waveguide. A porous high-order mode coupler characterized by being equipped with a frequency bandpass filter.