JPH0327601A - Polarization coupler - Google Patents

Abstract

PURPOSE:To absorb a polarized wave component not in use by providing 1st and 2nd circular waveguides, a square branch waveguide including a filter reflecting a high frequency signal and a conversion waveguide leading one of 2 linearly polarized wave signals to the square waveguide and absorbing and attenuating the other signal. CONSTITUTION:A horizontal polarized wave signal in 4GHz is coupled with a branched waveguide 23 with a slit 26, sent to a 4Ghz output terminal 28 through a band pass filter 27 and not coupled with a selective absorbing load 24. The 4GHz band vertical polarized wave signal is not coupled with the slit 26, coupled with a coupling loop 29 and absorbed to a resistive terminator 31 through a low pass filter 30. A 6GHz band vertical polarized wave fed to a 6GHz input terminal 32 is sent to a circularly waveguide 22 without being affected by a horizontal resistance plate 33 in a conversion waveguide 25 and not coupled with the coupling loop 29. Moreover, the wave is sent as it is to the circular waveguide terminal 34 without being affected by the slit 26. The 6GHz band horizontal polarized wave from the terminal 34 is not coupled with the branch waveguide 23 and the load 24 but enters the waveguide 22 and is absorbed by the resistance plate 33.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention converts two signals of different frequency bands transmitted through separate waveguides into two signals perpendicular to each other transmitted through one circular waveguide. This invention relates to a polarization splitter that converts directly polarized signals.

[Conventional technology]

In satellite communications, the uplink frequency that is transmitted from the earth station to the satellite and the downlink frequency that the earth station receives radio waves from the satellite are, for example, the 60H2 band and 4
Distant frequency bands such as the GHz band are used. Furthermore, in order to facilitate the separation of transmitting and receiving signals,
Polarizations orthogonal to each other are used for the amplifier link and downlink signals, and right-handed and left-handed circularly polarized waves are used in the 4/6 GH2 band of the Intelsat satellite, respectively.

Figure 4 is a perspective view showing an example of the configuration of a conventional primary radiator of a Cassegrain antenna that uses circularly polarized waves. It is structured from 3. In FIG. 4, a transmission signal 10 applied to input terminal 4
0 is a vertically polarized signal 101 from the circular waveguide section of the polarization splitter 3.
The signal is sent to the circularly polarized wave generator 2 as a signal.

Circularly polarized wave generator 2 has 9 polarized waves parallel to the plate and perpendicular to the plate.
A 90'' phase shift plate 5 that produces a phase shift difference of 0'' is provided at an angle of 45@, and a vertically polarized signal 101 is radiated from the conical horn 1 as a left-handed circularly polarized signal 102. The reflected wave from the sub-reflector (not shown) is a right-handed circularly polarized wave signal 1 whose traveling direction is opposite.
03, and when it passes through the circularly polarized wave generator 2, it becomes a horizontally polarized signal 104. The branch waveguide 6 that takes out the received signal includes a filter that reflects the transmitted signal, and the input terminal 4 cannot pass the horizontally polarized signal, so the horizontally polarized signal 10
4 is totally reflected and sent to the circularly polarized wave generator 2 again as a transmitted wave 10.
2 and is re-radiated as a right-handed circularly polarized wave component 105 in the opposite rotation direction. Therefore, it is not possible to improve the elliptically polarized wave ratio simply by improving the characteristics of the circularly polarized wave generator 2.

The same applies to reception, where the right-handed circularly polarized incident wave 200 becomes a horizontally polarized signal 201 by the circularly polarized wave generator 2.
The signal passes through the filter of the branch waveguide 6 and is output as a received signal 202 from the output terminal.

On the other hand, a left-handed circularly polarized wave input 203 that is perpendicular to the incident wave 200 becomes a vertically polarized wave signal 204 in the circularly polarized wave generator 2, and is not coupled to the branch waveguide 6, since it cannot pass through the waveguide in the <6GH2 band. , it is totally reflected and re-radiated as a left-handed circularly polarized wave signal 205, a part of which is re-received as a reflected wave 206 from the sub-reflector, and appears at the output terminal as an interference signal 207.

[Problem to be solved by the invention]

In the 4/6C; H2 band of Intelsat's V series satellites,
Orthogonal right-handed circularly polarized waves transmit different information using left-handed circularly polarized waves, and a frequency reuse method using orthogonal polarized waves is adopted in which frequencies are used twice. Of course, the earth station antenna in the band is used when the earth station transmits and receives both orthogonal polarizations, but even when the earth station does not use both polarizations and transmits and receives only a single polarization as before. ,
Good elliptical polarization is required. The first point to improve the elliptical polarization of the conventional primary radiator shown in FIG. 4, which transmits and receives only a single polarized wave, is to improve the characteristics of the circularly polarized wave generator, but as mentioned above, Elliptical polarization components are generated by reflected waves from sub-reflectors, etc., and it is not possible to obtain a good elliptical polarization rate only by changing the characteristics of the circular polarization generator. In particular, in Cassegrain antennas with small diameters, the reflection from the sub-reflector is large, and there is no effective means to suppress this. One way to solve this problem is to use the orthogonal polarization coupler shown in FIG. is to connect. In this case, 60H. The reflected wave 104 from the sub-reflector of the band transmission signal passes through the branch waveguide 13 of the 6GH2 band orthogonal polarization coupler 12 and is absorbed by the non-reflection terminator 11, so that almost no reflection occurs, so it becomes a right-handed circularly polarized wave. There is no radiation and the elliptical polarization is not degraded. Also, the vertically polarized signal 204 due to the left-handed circularly polarized wave input 203 of 4C;H2# is 4GH2
Vertical polarization branch waveguide 15.15 of band orthogonal polarization coupler 14
' and is absorbed by the non-reflection terminator 10.10', causing almost no reflection. Therefore, the re-radiation component 205 of the left-handed circularly polarized wave in FIG. 4 becomes very small, and the reflected wave 205 from the sub-reflector
6 can be ignored and the interference signal 207 disappears, 4C;H.
The incident wave 200 of the band is coupled to the horizontally polarized branching waveguide 16, 16', passes through the waveguide IT, 17' shown diagrammatically, and is combined in the hybrid l8 to form an output signal 208. Although this method can obtain a good elliptical polarization index, there is a problem that the structure of the 4GH2 band orthogonal polarization coupler 14 is complicated and the shape is large. The purpose of the present invention is to eliminate the above-mentioned problems, to construct an antenna primary radiation system that has a simple structure, absorbs unused polarization components, and has a good elliptical polarization even when there is reflection from the sub-reflector. The objective is to provide a polarization demultiplexer that can [Means for Solving the Problems] The polarization demultiplexer of the present invention includes a first circular waveguide that transmits signals in two high and low frequency bands, and an impedance transformer at one end of the first circular waveguide. a second circular waveguide that is connected to each other so that their central axes coincide with each other through the section and transmits only the signal in the high frequency band; and a slit in the tube axis direction provided in the tube wall near the impedance transformation section. The first
a rectangular branching waveguide that transmits the low frequency band signal and includes a filter that is coupled to the circular waveguide and transmits the low frequency band signal and reflects the high frequency band signal, and is opposite to the slit. The side pipe wall is coupled to the first circular waveguide by magnetic field coupling due to a circumferential magnetic field component or electric field coupling due to a radial direction electric field component, and the signal in the low frequency band passes through, and the signal in the high frequency band is transmitted. a selective absorption load from a reflective filter and a non-reflection terminator, and one of two orthogonal linearly polarized signals connected to the second circular waveguide and transmitted through the second circular waveguide. This is achieved by providing a conversion waveguide that transmits the waveguide to the rectangular waveguide and absorbs and attenuates the other waveguide.

[Effect]

According to this structure, high. It can absorb unused polarized wave components in each low frequency band, and can be applied to the primary radiator of a small Cassegrain antenna where there are many reflections from the sub-reflector.

〔Example〕

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

FIG. 1(a) is a perspective view of the first embodiment of the present invention, and FIG. 1(b) is a cross-sectional view, showing a first circular waveguide 20 capable of transmitting the 4,6C;H2 band; 6GHz'? A second circular waveguide 22 that passes only tF, and a first circular waveguide 20
A branching waveguide 23 is coupled to the 4CI{2 band horizontally polarized wave, and a branching waveguide 23 is provided on the opposite side to branch the horizontally polarized wave in the 4CI{2 band.
A conversion waveguide equipped with a selective absorption load 24 that absorbs vertically polarized waves in the 4GH2 band by loop coupling through φ, and a resistor plate that transmits vertically polarized waves in the 6GHz band to a rectangular waveguide and absorbs horizontally polarized waves. It is organized as 25.

The horizontally polarized signal in the 4GH2 band is coupled to the branch waveguide 23 through a slit 26 in the tube axis direction provided in the lower tube wall near the impedance transformation section 21 of the first circular waveguide 20, and then passed through the bandpass filter. 4GH2 output terminal 2 after passing through section 27
8. The horizontally polarized fundamental mode of a circular waveguide is
Near the upper wall of the circular waveguide where the coupling loop 29 of the selective absorption load 24 is provided, the magnetic field component H in the circumferential direction
Since there is no φ, no horizontal polarization is coupled to the selective absorption load 24.

The vertically polarized signal of the 4GH2 band is not coupled to the slit 26 because there is no axial magnetic field distribution on the lower tube wall, but is coupled to the coupling loop 29 by the circumferential magnetic field component Hφ of the upper tube wall, and the coaxial The non-reflection terminator 3 is passed through the shaped low-pass filter 30.
1 is absorbed.

The 5 GHzl vertically polarized wave applied to the 60H2 human power terminal 32 is transmitted to the circular waveguide 22 almost unaffected by the resistance plate 33 inserted horizontally into the conversion waveguide 25. Since the vertically polarized wave has a circumferential magnetic field component Hφ on the upper tube wall, it induces a voltage in the coupling loop 29, but the low-pass filter 3
0 is not coupled because it is a cutoff region, and since there is no axial magnetic field distribution H2 on the lower tube wall, it is transmitted as it is to the circular waveguide terminal 34 without being affected by the slit 26.

Similarly, the horizontally polarized wave in the 6GH2 band input from the circular waveguide terminal 34 enters the second circular waveguide 22 without being coupled to either the branching waveguide 23 or the selective absorption load 24 and is resisted. It is absorbed by the plate 33.

As is clear from the above explanation, the polarization splitter shown in Fig. 1 is
When a primary radiator is constructed by using it in place of the conventional polarization splitter 3 shown in the figure, the reflected wave 104 from the sub-reflector in the 6GH2 band
is absorbed by the resistor plate 33, so the right-handed circularly polarized re-radiated wave 1
05 is eliminated, and the vertically polarized signal 204 due to left-handed circular polarization in the 4GH2 band is absorbed by the selective absorption load 24, so the interference signal 207 is eliminated, and an antenna with good elliptical polarization for both transmitting and receiving can be configured. .

FIG. 2 is a perspective view of a second embodiment of the present invention. Here, the selective absorption load 35 is a waveguide type including a bandpass filter similar to a branch waveguide, and uses magnetic field coupling by circumferential slits, and the 6GH2 band conversion waveguide 36 is shown in FIG. 6
A non-reflection terminator is incorporated in the branch waveguide 13 of the GH2 band orthogonal polarization coupler 12. This configuration is the first
Although the shape is slightly larger than that of the embodiment, it can withstand high power transmission in the 6GH2 band, and has the effect of being simpler and smaller than the conventional example using the orthogonal polarization coupler shown in FIG.

In FIG. 3, the selective absorption load 24 in FIG. 1 is not loop-coupled but has electric field coupling by an antenna inserted in the radial direction in a circular waveguide, and magnetic field coupling by magnetic field distribution in the circumferential direction. Similar effects can be obtained by coupling only vertically polarized waves. Whereas strong magnetic coupling due to the circumferential magnetic field component is obtained at the end of the first circular waveguide,
In the case of electric field coupling, strong coupling is obtained at a location slightly away from the terminal (approximately 1/4 of the tube wavelength). In each of the above embodiments, it has been explained that the selective absorption load does not couple to horizontally polarized waves, but the horizontally polarized waves couple to the axial slit 26 in FIG. Even for higher-order modes that are locally induced within the circular waveguide, no electromagnetic field is generated that couples to the selective absorption load, so there is no coupling of both horizontal and vertical polarization. Further, in each of the above embodiments, the filter of the branch waveguide for the 4GH2 band is a bandpass filter, but a low-pass filter or a band-elimination filter may also be used. The same applies to filters with selective absorption loads, and the shapes of coupling loops are not limited to those shown. Also, 6 GHz
The configuration of the band conversion waveguide is not limited to that of the embodiment, and the structure of the conversion waveguide of the
The impedance transformation portion of the second circular waveguide may also have a structure other than the step structure of the embodiment, and there is no restriction on the length of the second circular waveguide. Furthermore, each structural part may be made of an integral structure, or may be connected by flanges or the like. [Effects of the Invention] As explained in detail above, the polarization demultiplexer of the present invention has a simple structure and can absorb unused polarization components in the high and low frequency bands. This has the effect of realizing a primary radiator of a small Cassegrain antenna with a simple structure, which has many reflections.

[Brief explanation of drawings]

FIG. 1(a) is a perspective view of a first embodiment of the polarization splitter of the present invention, FIG. 1(b) is a sectional view of the first embodiment of the present invention, and FIG. A perspective view of the embodiment, FIG. 3 is the third embodiment of the present invention.
FIG. 4 is a perspective view of the primary radiator of a conventional Cassegrain antenna using circular polarization, and FIG. 5 is a perspective view of an orthogonal polarization coupler using orthogonal polarization. 1... Conical horn, 2... Circularly polarized wave generator, 3...
Polarization splitter, 4... manual terminal, 5... 90° phase shift plate,
6, 13, 15.15'. 16.16'...Branch waveguide, 10.10'. 11... Non-reflection terminator, 12.1
4... orthogonal polarization coupler, 17.17'... waveguide,
18...Hybrid, 20.22...Circular waveguide, 2l...Impedance transformation section, 23...Branch waveguide, 24...Selective absorption load, 25...Conversion waveguide Pipe, 26...Slit, 27...Band filter, 2
8... Output terminal, 29... Coupling loop, 30...
Low-pass filter, 3l... Non-reflection terminator, 32... Input terminal, 33... Resistance plate, 34... Circular waveguide terminal, 35... Selective absorption load, 36... Conversion waveguide.
Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A first circular waveguide that transmits signals in two frequency bands, high and low; a second circular waveguide that transmits only signals in the frequency band; and a second circular waveguide that is coupled to the first circular waveguide by a slit in the tube axis direction provided in the tube wall near the impedance transformation section to transmit signals in the low frequency band. a rectangular branch waveguide that transmits the low frequency band signal and includes a filter that passes the signal of the high frequency band and reflects the signal of the high frequency band, and a magnetic field component in the circumferential direction on the tube wall on the opposite side to the slit. a filter coupled to said first circular waveguide by magnetic field coupling or electric field coupling with a radial electric field component to pass said low frequency band signals and reflect said high frequency band signals; and a non-reflection terminator. one of the two orthogonal linearly polarized signals connected to the second circular waveguide and transmitted through the second circular waveguide is transmitted to the rectangular waveguide, and the other is absorbed and attenuated. A polarization splitter characterized by comprising a conversion waveguide.