JPS5813057B2 - Interference wave cancellation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an interference wave canceling circuit for canceling interference waves in a communication system using two circularly polarized waves having anti-rotating relationships.

When two orthogonal linearly polarized waves are radiated into space via a 90° retardation plate (circularly polarized wave generator) and an antenna, they become two circularly polarized waves with anti-rotation relationships and propagate through space.

Therefore, if these two circularly polarized waves are received by another antenna and propagated through a 90° phase difference plate, they can be converted into two orthogonal two linearly polarized waves. Linearly polarized waves can be separated.

Figure 2 shows a conventional circuit that cancels out the interference waves and outputs only the desired polarized wave component when the antenna receives two elliptically polarized waves Vo and Ho as shown in Figure 1. show.

In Fig. 2, 1 to 4 are magic Ts constructed of rectangular waveguides, 5.6 are input terminals of magic T1 and magic T3, respectively, and 7 and 8 are magic Ts, respectively.
1 and a rectangular waveguide-shaped non-reflection termination connected to the output terminals of Magic T3, 9 to 12 are output terminals of Magic T2 and Magic T4, 13 and 14 are variable attenuators composed of waveguides, 15 , 16 is a variable phase shifter composed of a waveguide, 17 is a waveguide circuit connecting magic T1 and magic T2, and 18 is a variable attenuator 13 and a variable phase shifter 16.
19 is a waveguide circuit that connects Magic T3 and Magic T2 and includes a variable attenuator 14 and a variable phase shifter 15; 20 is a waveguide circuit that connects Magic T3 and Magic T2; 20 is a waveguide circuit that connects Magic T3 and Magic T2; This is a waveguide circuit that connects Magic T4.

In this configuration, since two waves are separated using orthogonality of polarization, two orthogonal polarized waves can be separated even if they have the same frequency, which is useful for effective use of the same wave number.

However, since the propagation space generally exhibits anisotropy due to rainfall, orthogonality is lost when the receiver is converted to linearly polarized waves, and one wave becomes the other at the output terminal of the polarization splitter. On the other hand, it becomes an interference wave.

Therefore, such a communication system requires a circuit that cancels out interference waves (compensates for cross-polarized waves).

In order to simplify the explanation, in this section 5, a method for canceling interference waves will be described assuming that two arbitrary elliptically polarized waves having a counter-rotating relationship are received by the antenna.

FIG. 1 is an explanatory diagram showing the state of a received wave, that is, an incident wave.

The x and y axes in the figure are orthogonal, and each axis coincides with the orthogonal branch axis of a polarization splitter that can separate orthogonal polarized waves.

Further, VO+ and Ho are names given to two arbitrary elliptically polarized waves having a counter-rotating relationship.

As described above, the two elliptically polarized waves have an arbitrary relationship, their elliptical polarization rates are different, and their tilt angles are not necessarily orthogonal.

In addition, Magic T1 allows the incident wave at input terminal 5 to be split into the waveguide circuits 17 and 18 with the same phase and equal amplitude, and Magic T3 allows the incident wave at input terminal 6 to be guided in the same phase and with equal amplitude. Magic T2 has the waveguide circuit 1 in which the incident wave from the output terminal 10 is in phase and has equal amplitude so that the wave is split into the tubes 19 and 20.
Magic T4 has the waveguide circuit 18 with the incident wave from the output terminal 11 having the same phase and equal amplitude so that the waves are split into 7 and 19.
and 20.

Now, a polarization splitter that can separate the polarization components orthogonal to the waveguide through which the Vo and Ho waves received by the antenna are propagated is installed, and the polarization components in the y-axis direction are input to the input terminal. 5
When the polarized wave component in the X-axis direction is introduced to the input terminal 6, the incident waves at the input terminals 5 and 6 can be expressed as shown in the first equation.

Incident wave at input terminal 5 = Voy + Hoy Incident wave at input terminal 6 = Vox + Hox Here, Voy and Vox are the electric fields of the y and x components of the Vo wave, respectively, and Hoy and Hox are the electric fields of the y and x components of the Ho wave, respectively.
and x component electric field.

The incident wave shown in the first equation can be expressed by an electric field at the output terminal 9 of the magic T2 and the output terminal 12 of the magic T4 as shown in the second equation.

Output wave of output terminal 9 = 1/2 (Voy + Hoy - α1 (
Vox+Hox)] Output wave of output terminal 12 = 1/2 (Hox+Vox-α2
(Hoy+Voy)] Here, α1 and α2 indicate the influence of the variable phase shifter and variable attenuator of the waveguide circuits 19 and 18, respectively.

Therefore, for example, Voy>Vox, Hox>Ho
If y, variable phase shifters 15, 16, variable attenuator 13
, 14, it is possible to realize the relationship Hoy=α1Hox Hox=α2Voy, so the output wave of the output terminal 12 is the fourth
As shown in the equation, only the Vo wave component can be branched to the output terminal 9 and only the Ho wave component can be branched to the output terminal 12.

In other words, interference can be canceled out. Output wave of output terminal 9 =
1/2 (Voy - α1 Vox) Output wave of output terminal 12 =
1/2 (Hox-(4)α2Hoy) Furthermore, in the case of Voy<Vox, Hox<Hoy, only the Ho wave component can be demultiplexed to the output terminal 9 and only the Vo wave component can be demultiplexed to the output terminal 12 in exactly the same way.

However, the above cancellation method has the disadvantage that the output terminals of Vo waves and Ho waves are reversed depending on the magnitude relationship between the y-component electric field and the x-component field.
As shown in the figure, a 90° retardation plate (circularly polarized wave generator) and a 180° retardation plate (polarized wave plane rotator) are also used together.

In the figure, 21 is an antenna, 22 is a polarization splitter, 23
2 is a waveguide circuit system shown in FIG. 2, 24 is a 90° phase difference plate, 25 is a 180° phase difference plate, and 28 is a waveguide circuit suitable for connecting each circuit component.

In addition, a 90° retardation plate 24 and a 180° retardation plate 25
are as indicated by the arrows in the figure (90° retardation plate,
It has a structure that allows rotation (180° around the tube axis of the retardation plate).

Therefore, in the circuit shown in FIG. 3, when the antenna 21 receives elliptically polarized waves of Vo and Ho as shown in FIG. As a result, two arbitrary elliptically polarized waves Vo and Ho can be converted into two elliptically polarized waves in which the long axis of the ellipse coincides with the orthogonal branch axis of the polarization splitter as shown in FIG.

Therefore, Voy>Vox and Hox>Hoy are always satisfied, and only the Vo wave component can be branched to the output terminal 9 and only the Ho wave component can be branched to the output terminal 12.

However, in the conventional interference wave canceling circuit, the 90° retardation plate 24, the 180° retardation plate 25, the variable attenuators 13, 1
4. It is necessary to control the variable phase shifter 15, 16, and the control mechanism is very complicated.
2, 3, 4, variable attenuators 13, 14, variable phase shifter 15,
There was a drawback that the waveguide circuit system consisting of 16 components was complicated.

In order to eliminate these drawbacks, the present invention halves the number of variable attenuators and variable phase shifters necessary for canceling interference waves compared to the conventional case, and will be described in detail below with reference to the drawings.

FIG. 5b shows an embodiment of the present invention.

In the figure, 26 and 27 are non-reflection terminations provided at the output terminals of Magic T3 and Magic T4, respectively.

The operating principle of FIG. 5b will be explained below.

Now, suppose that two elliptically polarized waves having a counter-rotating relationship as shown in FIG. 1 are received by the antenna T21.

In the conventional circuit configuration, as mentioned above, Vo and Ho are changed into two elliptically polarized waves whose long axes are orthogonal to each other, and the long axes are aligned with the orthogonal branching axes of the polarization splitter. was under control.

However, in this invention, the 90° retardation plate 24 and the 1
By controlling the 80° retardation plate 25, Vo, H
One of them is converted into a linearly polarized wave, and its plane of polarization is made to coincide with one of the axes of the polarized wave branches.

For example, if Ho is converted into a linearly polarized wave and the plane of polarization is made to match the x-axis of the polarization splitter 22, then Vo, Ho
The relationship between the waves is as shown in Figure 5a.

This kind of control is possible by rotating the 90° retardation plate 24 and the 180° retardation plate 25. This is because when the retardation plate 24 is rotated by 90° with respect to the polarization plane of linearly polarized waves, the 90° retardation plate This can be easily understood from the fact that the wave propagated through 24 changes from linear polarization to circular polarization, and that when the 1800 retardation plate 25 is rotated with respect to the polarization plane of linear polarization, the polarization plane rotates. .

Now, as mentioned above, the 90° retardation plate 24 and the 180°
The magic T controls the phase difference plate 25 and extracts only the wave polarized in the y direction among the orthogonal branches of the polarization demultiplexer 22.
When a branch that takes out only the wave polarized in the x direction is connected to the input terminal 5 of the magic T3, the input terminal 6 of the magic T3 becomes the following: Incident wave at the input terminal 5 = Voy Incident wave at the input terminal 6 = Vox + Hox.

Here, Voy and Vox are the electric fields of the y-direction and x-direction components of the Vo wave, respectively.

Further, Hox is the x-direction component electric field of the Ho wave, and in this case, the Ho wave is converted into a linearly polarized wave polarized in the x direction, so the incident wave at the input terminal 5 has no Ho wave component. Not included.

That is, the 90° retardation plate 24, 180 according to the present invention
° In the control of the phase difference plate 25, the incident wave at the input terminal 5 is Vo
There is only a wave component, and the Ho wave component, which is an interference wave, has disappeared.

Therefore, the interference waves that must be canceled are transmitted to the input terminal 6.
There are only Vox waves that are interference waves with respect to the Hox waves.

Therefore, a part of the output wave of the magic T1 is combined with a part of the output wave of the magic T3 via the variable phase shifter 16 and the variable attenuator 13 by the magic T4, and the condition of Vox=α2Voy (6) is satisfied. Then, only the Ho wave component can be extracted to the output terminal 12 of the magic T4.

Therefore, a signal wave that cancels out the interference wave appears at the output terminal 9 of the magic T1 and the output terminal 12 of the magic T4.

Although the above description has been made regarding received waves, it is clear from the reversibility of the circuit that the present invention can be applied not only to this but also to circuits on the transmitting side, and can also be used in antenna feeding circuits that share transmitting and receiving functions. You may.

Further, it is clear from the above-mentioned operating principle that a duplexer or a coupler may be used instead of the magic T.

As described above, in the interference wave canceling circuit according to the present invention, the number of variable phase shifters and variable attenuators required for canceling interference waves is reduced to half compared to the conventional case. The control device for nailing becomes simple.

Further, there is a great effect that the configuration of the three-dimensional circuit system is simplified.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing the state of an incident wave, Figure 2 is a diagram of a conventional interference wave canceling circuit, Figure 3 is a diagram explaining a conventional interference wave canceling method, and Figure 4 is a diagram showing the state of an incident wave. FIG. 5a is an explanatory diagram showing the state of an incident wave, and FIG. 5b is a circuit diagram showing an embodiment of the present invention. In the figure, 1 to 4 are magic T, 5 and 6 are input terminals, and 7 and 8
9 to 12 are output terminals, 13 and 14 are variable attenuators, 15 and 16 are variable phase shifters, 17 to 20 are waveguide circuits, 21 is an antenna, 22 is a polarization splitter, and 23 is a non-reflection termination. A waveguide circuit, 24 is a 90° retardation plate, 25 is a 180° retardation plate, 26 and 27 are non-reflection terminations, and 28 is a waveguide circuit. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

Claims (1)

[Claims] 1 In a waveguide that propagates two elliptically polarized waves that are in a counter-rotating relationship with each other, the phase of one of the two orthogonal polarized waves is changed by 90 degrees relative to the phase of the other polarized wave. and a 180° retardation plate that can change the phase of one of two orthogonal polarizations by 180 degrees with respect to the phase of the other polarization. When polarized splitters capable of splitting waves are connected by waveguides each having a rotation mechanism capable of rotating around the pipe axis of the waveguide, only one polarized wave of the polarized splitters is propagated in both X directions. The branch terminal is connected to a branch that propagates only a polarized wave orthogonal to the polarized wave of the polarization splitter through a plurality of Magic T1 variable attenuators and variable phase shifters, and the 90° phase difference plate, 180
°The rotation angle of the retardation plate is set so that at least one of the two elliptically polarized waves becomes a linearly polarized wave, and the linearly polarized wave is split into only one branch of the polarization splitter. An interference wave canceling circuit characterized in that the above-mentioned variable attenuator and variable phase shifter are controlled to cancel the interference waves.