JPS59117303A - Polarizer - Google Patents

Abstract

PURPOSE:To improve the factor of elliptical polarization of an antenna by providing a load absorbing only the polarized wave component due to a reflected wave sent from a sub-reflecting mirror to a polarizer used for a primary radiator of a Cassegrain antenna. CONSTITUTION:The 4GHz band of a reflected wave generated by the Cassegrain antenna sub-reflecting mirror is a left-handed circularly polarized wave and the 6 GHz band is a right-handed circularly polarized wave, and when the reflected wave is returned to the polarizer through a circularly polarized wave generator, the wave in the 4GHz band becomes a vertically polarized wave and the wave in the 6GHz band becomes a horizontally polarized wave. The vertically polarized wave in the 4GHz band enters the left side of a circular waveguide 20, because no magnetic field component exists in the lower guide wall the wave is not coupled to a slit of a branching waveguide 23 but coupled to a coupling loop 29 and passes through a coaxial low filter 30 and is absorbed in a resistive terminator 31. On the other hand, the horizontally polarized wave in the 6GHz band is not coupled by the branching waveguide 23 and the absorbing load 24 because of filters 27, 30 but absorbed in a resistance plate 33 in the 2nd circular waveguide 22.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for transmitting two different frequency bands through separate waveguides.
The present invention relates to a polarization splitter that converts one signal into two mutually orthogonal linearly polarized signals transmitted through one circular equal wave tube.

In satellite communications, the uplink frequency transmitted from the earth station to the satellite and the downlink frequency received by the radio waves from the satellite at the global station are, for example, 6G [(Z band and 4
Separate frequency bands such as the 0FIz band are used.

Furthermore, to facilitate the separation of transmit and receive signals, the uplink and downlink signals are polarized orthogonally to each other, and the Intelsat satellite's 4/60 Flz
In the band, right-handed and left-handed circularly polarized waves are used, respectively. Figure 1 is a perspective view showing an example of the configuration of the primary radiator of a conventional Cassegrain antenna used in solar radiation.
Circularly polarized wave generator 2 and polarization demultiplexer 3 using a 90° phase shift plate
It is composed of. In FIG. 1, a transmission signal 100 applied to an input terminal 4 is sent from a circular waveguide section of a polarization splitter 3 to a circularly polarized wave generator 2 as a vertically polarized signal 101. The circularly polarized wave generator 2 is provided with a 900 phase shift plate 5 inclined at 45°, which produces a 90° phase shift between polarized waves parallel to the plate and polarized waves perpendicular to the plate, and the vertically polarized wave signal 101 is left-handed. It is radiated from the conical horn 1 as a circularly polarized signal 102. The reflected wave from the sub-reflector is a right-handed circularly polarized wave signal 1 whose traveling direction is opposite.
When passing through the circularly polarized wave generator 2, the horizontally polarized signal 1
It becomes 04. The branching waveguide 6 that takes out the received signal includes a filter that reflects the sound of the transmitted signal, and further includes an input terminal 4.
cannot pass the horizontally polarized signal, so the horizontally polarized signal 104
is totally reflected and sent to the circularly polarized wave generator 2 again as a transmitted wave 102.
It is re-radiated as a right-handed circularly polarized wave component 105 in the opposite rotation direction. Therefore, there is a problem in that it is not possible to improve the elliptically polarized wave index by simply improving the characteristics of the circularly polarized wave generator 2. The same goes for reception, where 200 right-handed circularly polarized incident waves are converted into a horizontally polarized signal 201 by the circularly polarized wave generator 2, which passes through the filter of the branch waveguide 6' and outputs the received signal from the output terminal. It is output as 202. On the other hand, the incident wave 20
A left-handed circularly polarized wave input 203 that is orthogonal to Then, it is 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 as an interference signal 207 at the output terminal.

4/6 G ['(
ZW adopts a frequency reuse method using orthogonal polarization, which transmits separate information with orthogonal right-handed circularly polarized waves and left-handed circularly polarized waves, and uses the frequency twice.
GI (Z band earth station antennas are used when the earth station transmits and receives both orthogonal circularly polarized waves, but even if the earth station does not use circular polarization and transmits and receives only a single polarized wave as before) Even when transmitting and receiving only a single polarized wave, a good elliptical polarization is required. Regarding the improvement of the characteristics of the polarized wave generator, as mentioned above with reference to Fig. 1, all elliptical polarized wave components are generated by the reflected waves from the sub-reflector, etc., and it is not possible to improve the characteristics of the circularly polarized wave generator alone. It is not possible to obtain elliptical polarization.Especially in a Cassegrain antenna with a small diameter, 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 transmit and receive orthogonal circularly polarized waves. The orthogonal polarization coupler shown in Fig. 2 designed for the above is used, and non-reflection terminators 10.
1σ and 11. In this case, 6Gn
The reflected wave 104 from the sub-reflector of the Z-band transmission conventional broom is 6Gaz.
It passes through the branch waveguide 13 of the band orthogonal polarization coupler 12 and is absorbed by the non-reflection terminator 11, and there is almost no reflection, so there is no right-handed circular narrowing radiation and the elliptic narrowing ratio is not degraded.
A vertically polarized signal 204 from the GI (z-band left-handed circularly polarized wave input 203) is coupled to the vertically polarized branch guide 15 of the 4G z-band direct polarization coupler 14, the ego, and the non-reflection terminator 10. It is absorbed and almost no reflection occurs. Therefore, the re-radiation component 205 of the left-handed circularly polarized wave in FIG. G [(The incident wave 200 in the z-band is coupled into the horizontal narrow branch waveguide 16,1σ, and the waveguide 1'7.1 shown in the diagram is
7” (r, synthesized by hybrid 18 and output signal 2
It becomes 08. Although this method can obtain a good elliptical polarization index, it has the disadvantage that the structure of the 4 GHz band orthogonal polarization coupler 14 is complicated and the shape is large.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, to construct an antenna-order radiation system that has a simple structure, absorbs unused polarization components, and has a good elliptical polarization even when there is reflection from a sub-reflector, etc. The object of the present invention is to provide a polarization demultiplexer that can perform the following steps.

The polarization splitter 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 so that the signals coincide with each other and transmits all signals in the high frequency band; and a slit in the tube axis direction provided in the tube wall near the impedance transformation section to a rectangular branching waveguide that is coupled to the wave tube and transmits all of the low frequency band signals, including a filter that passes all of the low frequency band signals and reflects the high frequency band signals; and a tube on the opposite side of the slit. The first circular waveguide 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 electric field component at the wall, allowing all signals in the low frequency band to pass through and reflecting signals in the high frequency band. a selective absorbing load consisting of a filter and a non-reflection terminator;
a conversion waveguide that is connected to the circular waveguide and transmits two orthogonal linearly polarized signals transmitted through the second circular waveguide to one of the omnidirectional waveguides and absorbs and attenuates the other. Consisted of.

Next, the present invention will be described in detail with reference to the drawings.

4. FIG. 3(a) is a perspective view of the first embodiment of the present invention, and FIG. 3(b) is a sectional view. A first circular waveguide 20 that can transmit the 60Flz band, a second circular waveguide 22 that is connected via a stepped impedance transformation section 21 (il-) and that transmits only the 5GHz band, and a first A branching waveguide 23 is coupled to a circular waveguide 20 to branch horizontally polarized waves in the 4 GHz band, and a branching waveguide 23 is provided on the opposite side to split horizontally polarized waves in the 4 GHz band. It is composed of a selective absorption load 24 that absorbs waves, and a constant conversion waveguide 25 equipped with a resistive plate that transmits vertically polarized waves in the 6GI (z band) to a rectangular waveguide and absorbs horizontally polarized waves. 4GH
The z-band horizontally polarized signal is coupled to the branching 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 section. 27 and is transmitted to the 4 GHz output terminal 28. There is no magnetic field component Hφ in the circumferential direction near the upper tube wall of the circular waveguide where the horizontally polarized fundamental mode h of the circular waveguide and the coupling loop 29 of the selective absorption load 24 are provided. The waves are not coupled to the selective absorption load 24. The 4 GHz band vertically polarized signal has no axial magnetic field component on the lower tube wall and is not coupled to the slit 26, but is coupled to the coupling loop 29 by the circumferential magnetic field component Hφ of the upper tube wall, and is connected to the coaxial type. It passes through the low-pass filter 30f and is absorbed by the non-reflection terminator 31. The vertically polarized wave of the 60 Flz band applied to the 6 GHz input 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 all the circumferential low-field components Hφ on the upper tube wall, it induces a voltage in the coupling loop 29, but the low-pass filter 30 does not couple because it is in the cut-off region, and the lower tube wall has a low-field component Hφ in the axial direction. Slit 26 because there is no R field component Hz
The signal is transmitted as it is to the circular waveguide terminal 34 without being affected by the signal. The 6 GHz horizontally polarized wave inputted from the circular waveguide terminal 34 is similarly sent to the branch waveguide 23 and the selective absorption load 24.
It enters the second circular waveguide 22 without being coupled to any of them and is absorbed by the resistance plate 33.

As is clear from the above explanation, the polarization splitter shown in Fig. 3 is
When the primary radiator is completely configured by using it in place of the conventional polarization splitter 3 shown in the figure, the reflection 1104 from the sub-reflector in the 5 GHz band is absorbed by the resistor plate 33, so the right-handed circularly polarized wave is re-radiated trt
105 is eliminated, and the vertically polarized signal 204 due to left-handed circularly polarized waves in the 4 GHz band is absorbed by the selective absorption load 24, so the interference signal 207 is eliminated, and the entire antenna can be configured with good elliptical polarization for both transmitting and receiving. FIG. 4 is a perspective view of a second embodiment of the present invention, in which the selective absorption load 35 is of a waveguide type including a bandpass filter similar to a branch waveguide, and the magnetic field is generated by a circumferential slit. Using coupling, "6 G [(z-band conversion waveguide 36
It incorporates a non-reflection terminator. Although this configuration is slightly larger than the first embodiment, it is 60F.
It can withstand high power transmission in the lz band, and has the advantage of being simpler and smaller in size than the conventional example using the orthogonal polarization coupler shown in FIG. In FIG. 5, the selective absorption load 24 in FIG. 3 is not loop-coupled but has electric field coupling by an antenna inserted in the radial direction within a circular waveguide. Similarly, a similar effect can be obtained by coupling only vertically polarized waves. The electric field coupling due to the circumferential magnetic field component is the first
Strong coupling is obtained at the end of the circular waveguide, whereas in the case of electric field coupling, strong coupling is obtained at a location slightly away from the end (approximately 1/4 of the wavelength within the tube).

In the above description of the embodiment, it has been explained that the selective absorption load has no coupling for horizontally polarized waves, but horizontally polarized waves
Even for higher-order modes that are coupled to the axial slit 26 in the figure and locally induced within the circular waveguide by the electric moment generated there, an electric low field that couples to the selective absorption load 17 is generated. Therefore, there is no possibility of coupling of horizontal and vertical image polarizations.

In the above description of the embodiment, the filter of the branch waveguide for the 40h band is a bandpass filter, but it can also be constructed using a lowpass filter or a bandpass filter. The same applies to the selective absorption load filter, and the shape of the coupling loop is not limited to that shown in the drawings. Furthermore, the configuration of the 6GIlz conversion waveguide is not limited to that of the embodiment, and the impedance transformation portions of the first and second circular waveguides may also be of a structure other than the step structure of the embodiment. There are no restrictions on the length of the circular waveguide. Furthermore, each component may be made of a monolithic structure, and may be joined by seven flange or the like.

As explained in detail above, the polarization splitter of the present invention has a simple structure and can absorb unused polarization components in high and low frequency bands, thereby reducing the reflection from the sub-reflector. This has the effect of realizing the primary radiator of many small Cassegrain antennas with a simple configuration.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional primary radiator of a Cassegrain antenna that uses circular polarization, Figure 2 is a perspective view of an orthogonal polarization coupler that uses orthogonal polarization, and Figure 3 (a) is a perspective view of the present invention. FIG. 3(b) is a perspective view of the first embodiment of the polarization splitter of the present invention.
FIG. 4 is a perspective view of the second embodiment of the present invention, and FIG. 5 is a perspective view of the third embodiment of the present invention. Engineering...Conical horn, 2...Circular polarization generator, 3...Polarization splitter, 4.32...Group input terminal, End...・9° phase shift plate, 6. 13. 15.
IFj, 16. 1σ, 23...branch S
Wave tube, 10,1σ, 11.31... Non-reflection terminator, 12.14... Orthogonal polarization coupler. 17.17...Waveguide, 18...Hybrid, 20.22...Circular 4-wave tube, 21.
...Impedance transformation section, 24.35...
... Selective absorption load, 25.35 ... Conversion waveguide, 26 ... Slit, 27 ... Bandpass filter, 28 ... Output terminal, 29...
・Coupling loop, 30...Low pass filter, 33・
...Resistance plate, 34...Circular waveguide terminal. Shin 1 Diagram 4 Juku '3 Diagram

Claims (1)

[Claims] 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 intersecting linearly polarized signals connected to the second circular equal wave tube and transmitted through the second circular equal wave tube is transmitted to the rectangular exclusive tube, and the other is absorbed and attenuated. What is claimed is: 1. A polarization demultiplexer comprising a conversion waveguide for