JPS5840380B2 - Signature compensation method for cross-polarization interference - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to a cross-polarization interference discrimination compensation system. Due to factors such as polarization separators, feeder waveguides, antennas, and propagation space conditions (incident angle fluctuations, rainfall, etc.), the orthogonality of polarizations may be impaired, causing mutual interference between cross-polarized waves, resulting in poor line quality. This is a factor that degrades the transmission capacity and limits transmission capacity.

The present invention relates to a device that automatically compensates for mutual interference occurring between such cross-polarized waves, thereby improving line quality and further increasing transmission capacity.

Various methods have been proposed in recent years as methods for compensating for mutual interference between cross-polarized waves, and these can be roughly classified into the following two types.

(b) So-called orthogonality recovery, which reduces mutual interference between polarized waves by separating the polarized waves after recovering the orthogonality of the received waves whose orthogonality between polarized waves has deteriorated using an appropriate device at the receiving station. method.

(0) Focusing on the fact that due to the deterioration of orthogonality between crossed polarized waves, mutual interference occurs between the polarized waves and polarization interference waves are generated in each polarization output of the receiving station, and for this interference wave component, etc. Creates a compensation wave with an opposite amplitude and phase from the polarized wave on the interference source side and adds it to the polarized wave on the interfered side to cancel the interference wave component.
This is the so-called cross-compensation method.

However, none of these methods has yet been put into practical use.

The present invention aims to provide the cross-compensation method described in (b) above in a practical manner, and its feature is to create a compensation wave of equal amplitude and opposite phase from the interference source side polarization in accordance with the interference wave component. In order to add a compensation wave to the interfered wave and cancel the interference wave, the amplitude, polarity, and phase of the compensation wave are always adjusted appropriately according to the temporal fluctuations of the interference wave amplitude, polarity, and phase. The cross-compensation system has a means for automatic control to maintain the same, and will be described in detail below with reference to the drawings.

FIG. 1 is a basic configuration diagram of the cross compensation method.

Reference numeral 101 denotes a receiving antenna which receives cross-polarized signals (two orthogonal polarized waves having the same frequency are denoted by I and ■) sent out from a transmitting station.

102 is a polarization separator that separates polarization I and
.

If ■ is a counter-rotating circularly polarized wave, it is converted to orthogonal linearly polarized wave using a circular to linear polarization converter and then separated).

The separated polarized signals I and II are sent to receivers 106 and 10, respectively.
However, if the polarization (2) and the orthogonality of the river have deteriorated before reaching the antenna 1, mutual interference will occur and the line quality will deteriorate.

103, 103'. 104.104', 105 and 10
5 is a circuit for compensating such mutual interference, 103,
103' is a brancher, 104, 10 column combiner, 105゜1
05' is a device for controlling the amplitude and phase of the compensation wave to appropriate values, and is referred to as a compensation wave creation device.

The purpose of the compensation wave generating device is to generate a wave having the same amplitude and opposite phase to the interference wave component as a polarized wave on the interference source side.The conditions required for this device are as follows.

((4) In a normal state, that is, in a state where the orthogonality of the polarized waves (1) and (2) is perfect, there is no interference wave, so the compensation wave amplitude will be zero.

(d) The angle between polarized waves I and IF is 90° as shown in Figure 2.
The polarity of the polarized interference wave depends on whether it is smaller or larger than El.
, E′I′, so the polarity of the compensation wave is changed to the amplitude O
It must be possible to reverse the point at the border.

()) The amplitude of the compensation wave can always be controlled to be equal to the amplitude of the interference wave.

(Y) The phase difference between the polarized interference wave and the compensation wave generally changes from moment to moment, so the phase must be able to be controlled so that the phase difference can always be maintained at 180°.

(E) The above (I x mouth) ←) control is performed continuously and automatically.

FIG. 3 shows an embodiment of the configuration of a cross-compensation device according to the present invention, which can satisfy the above five conditions. Compensation on the polarization ■ side will be explained below (compensation on the polarization ■ side). (As is clear from the figure, the explanation is omitted because it is completely symmetrical to the polarization ■ side).

In FIG. 3, 1 is a receiving antenna, and 2 is a polarization separator.

16 and 16' are channel demultiplexers, but they have no direct relation to the present invention.

3, the cross section of the input and output ends is circular, as illustrated in FIG. 4a,
It is a waveguide with a rectangular central section, and both ends are supported by rotary joints (not shown), allowing the device to rotate around the tube axis.

The input wave electromagnetic field of this element is T E11 mode,
In the central square part, the output wave becomes T E10 mode again.
E, mode.

Assume now that the rectangular part of this element is inclined at an angle θ with respect to the horizontal plane as shown in Figure 4, and when a vertical electric field vector E is incident on it, the output of this element will be EC0.
Only the aθ component is output, and the E sinθ component cannot be output because it cannot pass through the rectangular waveguide.

4 is an orthogonal polarization separator, which will be explained later, and 5 is an orthogonal polarization separator as illustrated in FIG.
A, B, and the output of 3, Ecosθ
When input, as shown in the sectional view of FIG. 5, a component Ecos θ sin θ is applied to port A, and a component Es1rh2 θ is applied to port A.

The output appearing at baud)H is the communication wave energy of polarization 2, and is received by the receiver 9 via 8 in FIG.

The output of baud) A is part of the communication wave energy of polarized wave I, and is used as a compensation wave for canceling the interference wave component of polarized wave I contained in the polarized communication wave.

Let us show that among the five conditions mentioned above, three conditions (a) (0 scoop) are satisfied by devices 3 and 5.

First, if θ-0 is set, the output of A is Ee08θsinθ=O, and the condition (A) is satisfied.

Next, depending on whether the tilt angle θ is positive or negative, E co
sθsinθ is positive or negative.

That is, since the polarity is reversed, the condition (I:I) is satisfied.

Furthermore, the magnitude of Ecos θ sin θ can be continuously changed from 0 to the required value by changing θ, so the condition (c) is satisfied.

Next, the condition (-9) must be satisfied, which can be achieved by providing a variable phase shifter 7 in the compensation wave path to continuously vary the phase.

Thus 3. s, 7 makes it possible in principle to create compensation waves of equal amplitude and opposite phase to cancel the interference wave from the polarized wave I to the polarized wave (2).

However, in reality, the amplitude, polarity, and phase of the interference wave change from time to time, so the amplitude, polarity, and phase of the compensation wave must be automatically controlled accordingly.

To achieve this, we need an identification/judgment function that constantly identifies whether the amplitude, polarity, and phase of the currently applied compensation wave are appropriate, increases the amount of compensation if it is insufficient, and decreases the amount if it is overcompensated. It becomes necessary.

First, identification of amplitude and polarity will be explained.

4 plays an important role in this.

4 is a Faraday rotator, in which a rod-shaped ferrite is inserted onto the central axis of a circular waveguide, and a coil is wound around the outside of the waveguide to generate a magnetic field in the axial direction, as shown in Figure 6a. When the magnetic field is O, electromagnetic waves pass through without any effect on the plane of polarization, but when the magnetic field is turned off, the plane of polarization tilts (rotates), and if the direction of the magnetic field is reversed, the slope of the plane of polarization is also reversed. become.

Therefore, as shown in Figure 6, in 4, a wave E with an arbitrary plane of polarization is
(θ.

), and when an appropriate low-frequency alternating current is applied to the Faraday rotor coil to generate an alternating magnetic field, the polarization plane of the output wave in step 4 becomes (θ
1).

E(θ2).

Therefore, the input wave to the polarization separator 5 is as shown in FIG.

As shown in b and c, the slope of the polarization plane becomes a wave oscillating at a low frequency.

Now, when the plane of polarization changes from E(θ1) → E(θ1) → E(θ2), the output wave of port A is E1 in the state shown in Figure 7a.
→Eo-+E2, that is, the amplitude changes from small to dog.

Next, in the state shown in Figure 7, E1→Eo−+E2
That is, the amplitude changes from large to small.

Next, in the state shown in FIG. 7C (upright state), the output wave of the A port changes from EI to O-+E2.

From the above, when the inclination angle of the polarization plane changes vibrationally around a certain angle, amplitude modulation (AM) occurs in the A port output wave, and when considering the AM envelope in the three cases above, in a and b, the AM envelope It can be seen that the frequency is the same as the frequency of the alternating magnetic field, but the polarity of b is reversed with respect to a, and that of C is twice the frequency of the alternating magnetic field.

Therefore, by detecting the waveform of the AM envelope with the wave detector 12', it is possible to determine whether the slope of the plane of polarization is right half, left half, or upright.

Therefore, since the compensation wave must be 0 when there is no polarized interference wave under the condition (a) mentioned above, that is, the two-phase servo motor is set so that the inclination angle θ of the rotating waveguide 3 becomes O in the state C. 10 allows the tilt angle to be controlled.

Since this two-phase servo motor is driven by the output obtained by amplifying the detected waveform of the AM envelope by the amplifier 11, the first a
.

From the above, it can be seen that conditions (a) and (b) can be realized.

Next, we will consider the case where polarized interference waves exist, that is, the case (Ordinance No.).

The compensation wave is given as an amplitude modulated wave as shown by El j EOt E2 in FIGS. 7a and 7b.

For convenience of explanation, it is assumed that the phase difference between the polarized interference wave and the compensation wave is maintained at 1800 by a variable phase shifter 1, which will be described later.

Then, polarized interference wave E□ and compensation wave E1. As shown in Table 1 (a), (b), and (e), three cases can be considered for the vector composite diagram with Eo and E2.

Table 1 (a) shows the case of El>EO, that is, undercompensation, (b) shows the case of EI<Eo, that is, overcompensation, and (e) shows the case of E□=Eo, that is, proper compensation.

Table 1 (a) (b) (C) shows the composite vector in each case (a): E'1 = EI - El, E'o = E1 - Eo1
E'2-EI -E2 In 00, E'1=EI El, E'o=Eo EI
, g2=2 ET (.

In Ri, E'1=E4-El, E”o ”” E I
” o, E'2 = E2 E□.

As is clear from (a, (b, and C), the composite vector is also an amplitude modulated wave (AM wave). ), (b') have the same phase (small→large); and (C/), the AM has twice the frequency of the compensation wave AM.

Therefore, even when polarized interference waves exist, the two-phase servo motor 10 that drives the rotating waveguide 3 operates, and (
a') "(b)
A torque is generated to return the motor to its original position (in the C state, the torque becomes O and the motor stops.

From the above, it can be seen that appropriate compensation is automatically performed and condition (]) is satisfied.

Next, a method for automatically maintaining the phase difference between the polarized interference wave and the compensation wave at 1800 will be described.

For this purpose, the variable phase shifter 7 has a structure that can be controlled by a servo amplifier 13 and a two-phase servo motor 14, and a phase modulator 6 is provided in the circuit to apply phase modulation (PM) to the compensation wave at an appropriate low frequency. administer.

In this case, as mentioned above, the compensation wave has already been subjected to amplitude modulation, so in order to reduce mutual influence, the phase modulation frequency should be set to a different frequency, or the amplitude modulation and phase modulation should be set at an appropriate cycle using the switch 15. It is necessary to switch alternately ('''j'', ie, time-divisionally).

In this work, we will use the latter for convenience of explanation.

It is assumed that the amplitude of the compensation wave is automatically controlled to always be equal to the amplitude of the polarized interference wave.

There are three vector composite diagrams of the compensation wave subjected to PM and the polarization interference wave as shown in FIG. 8 ayb and c.

For the phase change of compensation wave φ1 → φ0 → φ2, vector composite liquid e1 → e (, → e2 is large → small in case of a, small → in case of b
In the case of dog C, it changes as e1 → 0 → e2.

That is, in either case, AM is generated in the resultant vector, and the phases of the AM envelopes in a and b are reversed, and the AM in the case of C is
The frequency will be twice the PM frequency.

Therefore, by driving 7 with a two-phase servo motor using the output obtained by detecting and amplifying this AM envelope, it is possible to always maintain state C, that is, the phase difference between the polarized interference wave and the compensation wave at 180°.

From the above, it can be seen that the condition (→) is satisfied.

Furthermore, from the above explanation, it can be seen that the condition m=tl is also satisfied because the amplitude control and phase control operations are performed continuously and automatically.

By applying the present invention to radio lines that use cross-polarized waves, it is possible to eliminate interference between polarized waves regardless of whether it is stationary or variable in time, and whether it is linearly polarized or circularly polarized. In addition, polarization interference waves can be canceled out, making it extremely useful for improving line quality, simplifying line configuration, and doubling transmission capacity by doubling the frequency with orthogonal polarization of the same frequency. It is effective and is particularly effective when applied not only to terrestrial lines but also to satellite communication lines.

[Brief explanation of the drawing]

Figure 1 is a basic configuration diagram of a conventional cross compensation system, Figure 2 is a vector diagram of polarized interference waves, Figure 3 is an example of a configuration of a cross compensation system according to the present invention, and Figure 4a is a diagram of the configuration of a cross compensation system according to the present invention. 4 is a conceptual diagram of the rotating waveguides 3 and 3', FIG. 4 is an electric field vector diagram in the rectangular waveguide portion of the rotating waveguide, and FIG. Figure 5 is a conceptual diagram of 5', and Figure 5 is an electric field vector diagram in the circular waveguide section of the orthogonal polarization separator.
Diagram a. b and C are the Faraday rotator 4゜L in Fig. 3.
Diagrams illustrating the concept and electric field vectors; Figures 7a, b, and C are diagrams illustrating the electric field vectors of the Naraday rotator output waves in the circular waveguide section of the linearly polarized wave separators 5 and 5 in Figure 3; 8a, b and C are phase modulators 6 in FIG.
．． FIG. 3 is a vector composite diagram of a compensation wave that has undergone phase modulation due to a polarization interference wave; (Explanation of symbols; Fig. 3), 1; receiving antenna, 2; polarization separator, 3, 3'; rotating waveguide, 4. A; Faraday rotator, 5, 5'; orthogonal polarization separator, 6, 6'; phase modulator, 7. T; variable phase shifter, 8, 8'; coupler, 9, 9
'; Receiver for polarized waves I and II, 10.・101°14.1
4'; Servo motor, 11, 11', 13F 13'; Servo amplifier, i2, 12'; Envelope detector, 15, 1
5'; Switcher.

Claims (1)

[Claims] This system has the following first-order configuration, and automatically generates a compensation wave having the same amplitude and opposite phase as the interference wave from the wave on the interference source side for polarized interference waves in a wireless communication line using cross-polarized waves. A method for identifying and compensating for cross-polarization interference, which is characterized by creating a polarization interference wave and canceling the polarization interference wave by combining it with a polarization interference wave; (a) Polarization wave separating a received signal into each polarization wave; vessel, (b
) As a means of creating a compensation wave to cancel the polarization interference wave that appears on the polarized output of the interfered side for each polarized wave, it is possible to rotate around a tube axis with a circular input and output cross section and a square central cross section. Compensation wave creation means using a rotating waveguide and an orthogonal polarization separator provided on its output side; (e) A Faraday rotator is inserted between the rotating waveguide and the orthogonal polarization separator, and an appropriate By applying a low-frequency alternating magnetic field, the polarization angle of the output wave of the rotating waveguide is alternately changed at a low frequency, thereby changing the amplitude of the low frequency to the compensation wave of the orthogonal polarization separator output. means for modulating a compensation wave that causes modulation; (d) the low frequency of the envelope of the amplitude modulation in item (e) above is twice the frequency of the alternating magnetic field when the residual polarization interference wave is minimized; and By utilizing the fact that the polarity of the amplitude modulation envelope is reversed at this point, the amplitude and polarity of the residual polarized interference wave can be identified by envelope detection of the residual polarized interference wave. polarity identification means, (e) automatically adjusts the amount of rotation of the rotating waveguide based on the information on the amplitude and polarity of the residual polarized interference wave in item (d) above so that the residual polarized interference wave is always minimized; (f) a rotating waveguide control means configured to control the amplitude of the compensation wave by controlling the amplitude of the compensation wave; The amplitude modulation envelope generated in the composite liquid of the compensation wave and the polarized interference wave becomes twice the frequency of the modulation low frequency at the point where the composite phase is 1800, and the amplitude modulation envelope increases from this point as a boundary. Compensation wave phase control means that always maintains the phase difference between the compensation wave and the polarized interference wave at 180° by controlling an electric phase shifter provided in the compensation wave circuit using polarity reversal.