JPS6021498B2 - Cross polarization compensator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a cross-polarization compensator in a communication system using two circularly polarized waves having an anti-rotating relationship with each other or two orthogonal linearly polarized waves.

For convenience of explanation, a cross-polarization compensator in a communication system using two circularly polarized waves having anti-rotating relationships will be described as an example.

When one orthogonal linearly polarized wave is radiated into space through a 90° phase difference plate (circularly polarized wave generator) and an antenna, it becomes two circularly polarized waves having anti-rotating relationships and propagates in space.

Therefore, if these two circularly polarized waves are received by another antenna and passed through a 90o retardation plate, they can be converted into one orthogonal linearly polarized wave again. Polarization can be separated.

This communication method uses orthogonality of polarization to separate two waves, so even if two orthogonal polarized waves have the same frequency, separation is possible, and effective frequency utilization can be achieved. However, in general, the propagation space exhibits anisotropy due to rain or the like, so the orthogonality between the two polarized waves is lost, and cross-polarized components are generated, which become interference waves.

The anisotropy of the rainfall area is caused by the ellipsoidal shape of raindrops.
iferential, PhaseShM (hereinafter referred to as DP
(abbreviated as S) and Diff Rental Attenua
tion (hereinafter abbreviated as DA).

For this reason, the conventional cross-polarization compensator was constructed as shown in FIG. In Fig. 1, 1 is a transmitting and receiving antenna, 2 is a group demultiplexer that separates the transmitting and receiving waves, and 3 is a rotatable 9
A polarization conversion circuit composed of a combination of a 0o retardation plate and a rotatable 180o retardation plate, 4 a polarization splitter, 5 a coupler, 6 a variable phase shifter, 7 a variable attenuator, 8 and 9 are receiving terminals, 10 is a cross-polarization compensator for the transmitting band based on the same operating principle as that for the receiving band, and 11 is an interference wave cancellation circuit composed of a coupler 5, a variable phase shifter 6, an attenuator 7. be.

Now, consider a case where circularly polarized waves, polarized waves A and B, which are in a counter-rotating relationship with each other, are transmitted from opposing antennas.

When the polarized waves A and B pass through the rainy region, the waves incident on the antenna 1 become two elliptically polarized waves with anti-rotation directions, as shown in FIG. Note that in the figure, X and Y indicate the directions of two orthogonal terminals of the polarization splitter 4. At this time, the 900 phase difference plate 180o phase table plate constituting the polarization conversion circuit 3 is rotated so that the polarized wave A becomes a linearly polarized wave that coincides with the X axis of the polarization splitter 4 as shown in FIG. When controlled so that it is converted into It is taken out as.

Therefore, the polarized wave B component at the Y terminal is split by the coupler 5, and is made into equal amplitude and opposite phase to the polarized wave B component at the X terminal by the variable phase shifter 6 and the variable attenuator 7. When combined, only the polarized wave A component can be taken out at the receiving terminal 9 of the interference wave canceling circuit 11.

However, this method requires a drive mechanism for adjusting the phase and amplitude in the interference wave circuit 11, which has the disadvantage of increasing the probability of failure.

In order to eliminate these drawbacks, the present invention fixes the variable phase shifter 6, and will be described in detail below with reference to the drawings.

FIG. 4 shows an embodiment of the present invention, in which 1 to 5 and 7 to 11 are the same as in FIG. 1, and 12 is a fixed phase shifter instead of the variable phase shifter 6 in FIG. This is what I did.

Now, considering the receiving plate, if the 90o phase difference plate of the polarization conversion circuit 3 is set on the most axis of the incoming polarized wave A, the polarized wave A is converted to the road polarized wave.

When the 1800 retardation plate of the polarization conversion circuit-3 is rotated to the angle between the polarization plane of this linearly polarized wave and the X terminal of the corner splitter 4, the polarized wave A is The road polarization matches the × terminal.

At this time, the other polarized wave B that received the DPS and DA of the rain is
It becomes a bridge circularly polarized wave and is coupled to both the X and Y terminals of the polarization splitter 4.

The phase difference between the polarized B components coupled to the X and Y terminals is expressed by the following equation, where 0 is △ and DA is △L (unit ship). o=gei-tan-1{nenh(0-11513△L)
/ Thin △○} ---(1
) This phase difference 8 is a problem because ΔL is sufficiently small compared to Δ◇ in the 4 and 60 Hz bands used for satellite communications and the like.

Also, for changes in rainfall intensity, △L and △? changes almost proportionally, so the change in the phase difference a is small. Therefore, if the phase shifter 12 of the interference wave canceling circuit 11 is fixed at the optimum phase shift amount, the number of drive mechanisms can be reduced compared to the conventional one without impairing the performance of the interference wave canceling circuit 11, and the failure probability can be reduced. A simple cross-polarization compensator can be obtained.

Although the configuration in which the variable attenuator 7 is used in the interference wave cancellation circuit 11 has been described above, the coupler 5 connected to the terminal 9 may be replaced with a variable coupler and the variable attenuator 7 may be removed.

Furthermore, although the above description has focused on the receiving system, it is clear that the invention can also be applied to the transmitting system. As described above, according to the present invention, the number of driving mechanisms for the interference wave canceling circuit 11 can be reduced compared to the conventional one, so that it is possible to obtain a cross-polarization compensator with a simple structure and high reliability.

Brief explanation of the drawings Figure 1 is a configuration diagram of the secondary cross-polarization compensator, Figures 2 and 3 are state diagrams of bridge circular polarization to explain the operating principle, and Figure 4 is a diagram of the configuration of the secondary cross-polarization compensator. FIG. 1 is a configuration diagram of a cross-polarization compensation device showing an embodiment of the invention.

In the figure, 3 is a polarization conversion circuit, 4 is a polarization splitter, 5 is a coupler,
6 is a variable phase shifter, 7 is a variable attenuator, 11 is an interference wave cancellation circuit, and 12 is a fixed phase shifter.

In the drawings, the same or corresponding parts are denoted by the same reference numerals. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 Consists of a variable 90° retardation plate and a 180° retardation plate, which can change the polarization of the polarized signal passing therethrough from linear polarization to circular polarization, and can also change the plane of polarization by 180°. a wave converter, a polarization splitter that distinguishes and outputs polarization components in two orthogonal X-axis and Y-axis directions of an input polarization signal, and an X-axis output terminal of the polarization splitter; and an interference wave canceling circuit that adjusts the component of and combines it with the component of the Y-axis output terminal and cancels the component of the Y-axis terminal included in the component of the X-axis output terminal. In the cross-polarization compensator for dual polarization of signal B, the direction of the setting axis of the 90° phase shift plate is set to match the long axis of polarization signal A, and the polarization signal A is converted into linear polarization. , adjusting the 180° phase shift plate that receives the output signal of the 90° phase shift plate so that the angle is 1/2 of the angle between the polarization plane of the linearly polarized wave and the X-axis terminal of the polarization splitter. After obtaining the X-axis terminal output and the Y-axis terminal output, the phase shift amount of the X-axis terminal output is fixed at an optimal setting around π/2, and the amplitude is adjusted.
A cross-polarization compensator characterized in that a cross-polarization compensator extracts only an A polarization component by combining it with a shaft terminal output.