JPS60233902A - Attenuator for spurious mode - Google Patents

Abstract

PURPOSE:To attain low loss transmission of a large power signal by inserting a resistor in two sets of sub-waveguide provided to a guide wall in parallel with the TE10 or the TE01 wave so as to attenuate entirely the spurious mode having a low cut-off frequency except the mode to be transmitted. CONSTITUTION:The 1st sub waveguide 3 is connected to a main waveguide 1 with a slit in the direction of the guide axis (z) provided to the short side guide wall vertical to an electric field of the TE01 wave propagated in the main waveguide 1 and only the basic mode is propagated. The 2nd sub waveguide 5 is connected by means of many slits 4a, 4b provided to the long side guide wall in parallel with an electric field of the TE01 wave of the main waveguide 1. Resistor boards 6, 7 are provided respectively in parallel with the electric field in the sub waveguides 3, 5. Thus, all spurious modes having a low cut-off frequency except the mode to be propagated are attenuated. Thus, the propagation of low loss for a large power signal is attained.

Description

[Detailed Description of the Invention] [Technical Field] The invention of the present application is used to perform low-loss transmission of high-power signals using an unnecessary mode attenuator, especially an oversized waveguide capable of transmitting higher-order modes. This invention relates to an unwanted mode attenuator.

[Prior art]

Waveguides with a rectangular cross section used for microwave band transmission are usually used to transmit only the fundamental mode, but as the frequency increases, the waveguide cross section becomes smaller and the transmission loss increases. In recent years, the development of high frequency bands in microwave wireless communication systems has progressed rapidly, and quasi-millimeter wave frequencies such as 11/14 GHz and 18/26 GHz have come into practical use in satellite communications. Along with this, transmission loss in a waveguide connecting a transmitter and an antenna has become a problem in uplink transmission from a ground station to a satellite. In order to reduce the transmission loss of waveguides, it is known to perform low-loss transmission using an oversized waveguide with a large cross section that can transmit higher-order modes. When both ends of the waveguide are connected to a waveguide that transmits only the fundamental mode through a tapered waveguide,
Once generated, the higher-order mode is reflected by the tapered waveguide at both ends, causing resonance within the oversized waveguide, resulting in a confined resonance phenomenon in which transmission loss rapidly increases at that frequency. In order to avoid this, it is necessary to insert an unnecessary mode attenuator to attenuate the generated higher-order modes. Conventionally, this type of unwanted mode attenuator is known by inserting a resistive plate into the electric field at the same direction as the TEol wave (or TElo wave) used for signal transmission. It is not possible to attenuate the TEoz wave (or TEzo wave), which has only an electric field component, and since a thin resistive plate is inserted into the main waveguide, there are problems with its mechanical strength and heat dissipation/retention method. The disadvantage is that it is not suitable for power transmission. Similarly, when transmitting TE 11 waves in a circular waveguide, there is a drawback that one of the two orthogonal TEzl waves cannot be attenuated by a resistor plate inserted diametrically perpendicular to the electric field.

[Purpose of the invention]

The purpose of the invention of the present application is to be able to attenuate all unnecessary modes with low cutoff frequencies other than the mode to be transmitted without inserting a resistor into the main waveguide, and to eliminate the above-mentioned drawbacks. An object of the present invention is to provide an unnecessary mode attenuator suitable for power transmission.

[Structure of the invention]

The first invention of the present application provides a main wave tube having a rectangular cross section capable of transmitting higher-order modes, and a center of the tube wall perpendicular to the electric field of the TE111 wave or TEos wave used for signal transmission within the main wave tube. A first sub-waveguide coupled via an elongated coupling hole provided in the tube axis direction, and a plurality of elongated waveguides provided in the tube wall parallel to the electric field of the TEjo wave or TEol wave parallel to the electric field. It is configured by including a second sub-waveguide coupled through a coupling hole, and a radio wave absorber provided in each of the first and second sub-waveguides.

The second invention of the present application provides a main waveguide having a circular cross section capable of transmitting higher-order modes, and a diametrical pipe wall that contains an electric field of TE11 waves used for signal transmission in this main waveguide in the pipe axial direction. a first sub-waveguide coupled to the main waveguide through an elongated coupling hole provided in the main waveguide; and a plurality of circumferences provided on the tube wall of the main waveguide with the coupling hole rotated by 90 degrees. A second sub-waveguide coupled to the main waveguide through an elongated coupling hole in the direction, and a radio wave absorber provided in each of the first and second sub-waveguides. be done.

[Embodiment of the first invention] Next, each invention of the present application will be described in detail with reference to the drawings.

FIG. 1 is a partially cutaway perspective view of a first embodiment of the first invention of the present application, and shows a main wave tube l with a rectangular cross section capable of transmitting higher-order modes, and a main wave tube l that transmits a high-order mode. T Eo1
A first sub-waveguide 3 that is coupled to the main waveguide 1 through a slit 2 in two directions of the tube axis provided in the short side tube wall perpendicular to the electric field of the wave and transmits only the fundamental mode, and a first sub-waveguide 3 that transmits only the fundamental mode; A large number of strips are installed on the long tube wall parallel to the electric field. J Tsu) 4a
.

4b, and resistance plates 6 and 7 provided in parallel to the electric field in the sub waveguides 3 and 5, respectively.
It is composed of. In Figure 1, the higher-order mode 'l'got wave used for signal transmission in the main waveguide 1 is
In the center of the short tube wall, the tube axis 2
There is no magnetic field component in the X direction (current component in two directions) on the long side tube wall. Therefore, the signal is transmitted within the main waveguide without being affected by the slit 2 and the slits 4a and 4b. On the other hand, Tg
Since the higher-order mode TEOZ wave, which has only the same electric field component as the OX wave, has only magnetic field components in two directions at the slit 2, it is coupled to the first sub-waveguide 3 by the slit 2 and absorbed by the resistive plate 6. Ru. The higher-order mode that can be transmitted in the main waveguide l has a rectangular cross section whose long side length a is 2 times the short side length b.
In the case of double (a = 2b), the first
It will look like a table. Here, of the two subscripts for each mode, the former represents the degree of distribution in the long side direction, and the latter represents the degree of distribution in the short side direction. Each mode TEmn shown in Table 1.

Among T M m fl, the transmission mode of the main waveguide TEo
Each mode except for the l-wave in Table 1 and the TEoz wave mentioned above has a magnetic field component in the X direction on the long tube wall, and if m is an odd number, the magnetic field component has a maximum value on the center line of the tube wall. It is coupled to the second sub-waveguide 5 by a row of coupling holes 4a arranged on the centerline, and if m is an even number, there is no magnetic field component in the X direction on the centerline, but The higher-order mode 'l' is transmitted to the second sub-waveguide 5 by the two rows of coupling holes 4b.
It is combined with the Ezo wave and absorbed by the resistor plate 7. or,
Among TEmn, each mode where n is an even number is TEo described above.
Like the z-wave, it has bidirectional magnetic field components at the center of the long-side tube wall, so it is also coupled to the first sub-waveguide 3. Each coupling hole 4a,
4b does not affect the transmission mode TEor wave of the main waveguide, so the length of the coupling hole can be selected close to half the wavelength of the frequency used, and there is no problem in strengthening the coupling by using the resonance phenomenon, and it is short. The required attenuation can be obtained by adjusting the length. According to Jin's configuration, there is no insert such as a resistor plate in the main wave tube.
There are no restrictions on the thickness of the resistor plate inserted into the sub-waveguide, so it can be held in any way, and heat dissipation measures are easy, making it suitable for transmitting large amounts of power.

FIG. 2 is a partially cutaway perspective view of the second embodiment of the first invention of the present application, and similarly to FIG. be.

In FIG. 2, the first sub-waveguides 13 are connected through a plurality of coupling holes 12 elongated in the tube axis direction, and the resistance plates 16 are separately attached to both ends of the sub-waveguides. The central part without a resistance plate has the effect of strengthening the coupling based on the principle of a porous directional coupler. That is, if the length C of the long side of the sub-waveguide 13 is 2C=b, the higher-order mode TEOZ wave transmitted through the main waveguide and the fundamental mode T transmitted through the sub-waveguide 13
Since the in-tube wavelengths of E>o waves are almost the same, even if the coupling degree of one coupling hole is small, most of the Tgox waves transmitted through the main waveguide can be coupled to the sub waveguide 13 with an appropriate length. can be done. Further, the second sub-waveguide has sub-waveguides 15a coupled through coupling holes 14a arranged on the center line of the long side tube wall, and two rows of coupling holes 14b arranged symmetrically about the center line. A sub-waveguide 1 consisting of two waveguides that transmit only the fundamental mode, which are coupled together and separated by a metal partition wall 18 whose center is indicated by a broken line.
5b. In this example, TEmn,
Among the TEmn waves, those where m is an odd number are mainly transmitted to the sub waveguide 1.
5a, those in which m is an even number are configured so that they are mainly coupled to and absorbed by the sub waveguide 15b.

FIG. 3 is a perspective view including a cross section of the third embodiment of the first invention of the present application, in which the main waveguide 21 has a fundamental mode TEL.
The case where o-waves are transmitted is shown. As shown in the figure, the first sub-waveguide 23 is a thin waveguide, and one side wall of the first sub-waveguide 23 is a slit 22 provided at the center of the long side wall of the main waveguide. is coupled to the main waveguide, and the radio wave absorber 2
6 absorbs the TE20 wave. Second sub-waveguide 25
are coupled through a coupling hole 24 in the short side tube wall of the main wave tube,
TEor, TEtt shown in Table 1 by the resistance plate 27
.

Absorbs each mode of TMlt, TEzx, and TMzx.

The TEso wave, like the TEzo wave, is not coupled to any sub-waveguide and is not attenuated, but TE2 (TEs including l).

It is possible to attenuate each of the above-mentioned higher-order modes having a long cutoff wavelength.

[Embodiment of the second invention] Fig. 4 is a block diagram showing the configuration of an embodiment of the second invention of the present application, in which the same technical idea as the three examples above is applied to a main wave tube with a circular cross section. This is what I did. In FIG. 4, the fundamental mode TEJI wave transmitted in the main waveguide 31 has an electric field indicated by the arrow, and the first sub-waveguide 33 has a diameter (X
The second sub-waveguide 35 is connected to the main waveguide 31 through a slit 32 in the tube axis direction provided on the tube wall above the y-axis, and the second sub-waveguide 35 is connected to the main waveguide 35 through a circumferential slit 32 provided on the tube wall that intersects with the y-axis. 34 (dashed line) with the main waveguide 31, and each resistor plate 36.
It is equipped with 37. Each higher-order mode transmitted within the circular waveguide has an electromagnetic field distribution as shown in Figure 5, and the TE11 wave used for signal transmission is divided into two waves on the tube wall on the X-axis where the slit is provided. The directional magnetic field is transmitted without being coupled to the sub-waveguide because the tube wall on the y-axis does not have a circumferential magnetic field. On the other hand, the orthogonal TElt wave, which is perpendicular to the TE11 wave, has a bidirectional magnetic field on the tube wall on the X axis and a circumferential magnetic field on the tube wall on the y axis, and has a circumferential magnetic field on the tube wall on the y axis. 35
is coupled to and attenuated. TMol wave of each higher order mode.

Both the TE21 wave and the orthogonal TE21 wave have magnetic field components in two directions on the tube wall on the X-axis, or magnetic field components in the circumferential direction on the tube wall on the y-axis. It binds to and is absorbed by either. Therefore, according to the configuration of this embodiment, it is possible to attenuate unnecessary modes, including the orthogonal TE21 mode, which cannot be absorbed by the resistor plate inserted on the y-axis perpendicular to the electric field of the TElt mode transmitted in the main waveguide. I can do it.

In the above-described embodiment of the first invention, the main waveguide with a rectangular cross section has a long side to short side ratio of 2. b
The technical idea of the present invention can also be applied to a waveguide with a square cross section. Father, in each of the embodiments of the first and second inventions described above, the first and second sub-waveguides are provided at the same position in the pipe axis direction of the main waveguide, but each sub-waveguide is The tubes are not limited to the same position, and may be provided at different positions. Furthermore, the cross-sectional shape of the sub-waveguide is not necessarily limited to the rectangular cross-section of the embodiment.

〔Effect of the invention〕

As explained in detail above, according to the unnecessary mode attenuators of the inventions of the present application, the first and second modes are connected by an elongated coupling hole in the axial direction and in the direction perpendicular thereto, which do not affect the mode to be transmitted. The sub-waveguide allows unnecessary modes other than the transmission mode to be attenuated without inserting a resistive plate into the main waveguide, and has the effect of configuring an unnecessary mode attenuator suitable for transmitting high-power signals. .

[Brief explanation of drawings]

FIG. 1 is a partially cutaway perspective view of a first embodiment of the first invention of the present application, and FIG. 2 is a partially cutaway perspective view of the second embodiment of the first invention of the present application. 3 is a perspective view including a cut section of the third embodiment of the first invention of the present application, FIG. 4 is a configuration diagram of an embodiment of the second invention of the present application, and FIG. It is a mode explanatory diagram of a circular waveguide. 1.11,21,31... Main wave tube, 2,12
゜22.32, 4a, 4b, 14a, 14b, 24゜Conflict zfJ I 3 Possible

Claims (1)

[Claims] (1) A waveguide with a rectangular cross section capable of transmitting higher-order modes, and a TElo that can be used for signal transmission within this main waveguide.
a first sub-waveguide coupled to the main waveguide through an elongated coupler provided in the tube axis direction at the center of the t-wall perpendicular to the electric field of the T E lo wave or the T E lo wave; The electric field F of the TEos wave is coupled to the main waveguide through a plurality of elongated coupling holes provided in the tube wall parallel to the electric field, and the broken second sub-waveguide is connected to the first and second sub-waveguides. An unnecessary mode attenuator characterized by comprising a radio wave absorber provided in each waveguide. (2) The unnecessary mode attenuator according to claim 1, wherein the first and second sub-waveguides are provided at the same axial position of the main waveguide. (3) The signal wave transmitted within the main waveguide is T E
ox wave, the second sub-waveguide has at least TE
A thin rectangular waveguide capable of transmitting lo waves and TEzo waves, including one row of coupling holes arranged on the centerline of the main waveguide tube wall and two rows of coupling holes arranged symmetrically about the centerline. Claim 1 or 2, characterized in that
Unwanted mode attenuator as described in section. , (4) A main wave tube with a circular cross section capable of transmitting higher-order modes, and a TE used for signal transmission within this main wave tube.
a first sub-waveguide coupled to the main waveguide through an elongated coupling hole provided in the tube axis direction in the tube wall on the diameter containing the electric field of 11 waves; a second sub-waveguide coupled to the main waveguide through a plurality of circumferentially elongated coupling holes provided on a tube wall rotated by 90 degrees with respect to the main waveguide;
An unnecessary mode attenuator comprising a radio wave absorber provided in each of the first and second sub-waveguides. (5) The unnecessary mode attenuator according to claim 4, wherein the first and second sub-waveguides are provided at the same position in the axial direction of the main waveguide.