JPH0219658B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cross-polarization compensator for orthogonal two-polarization sharing technology in satellite communications and the like.

[Conventional technology]

FIG. 4 is a block diagram showing a downlink system of a conventional cross-polarization compensator.
is an antenna, 2 is a group splitter, 3 is a 90° phase difference plate,
4 is a 180° retardation plate, 5 is a polarization splitter, 6 is a 90° retardation plate angle detector, 7 is a 180° retardation plate angle detector,
8 is a 90° retardation plate drive mechanism, 9 is a 180° retardation plate drive mechanism, 10 and 11 are couplers, 12 is a receiver, 1
3 is a servo control circuit, 14 is a clear weather stop detection circuit,
24 is a receiving system right rotation terminal, 25 is a receiving system left rotation terminal,
28 is a 90° retardation plate angle output terminal, 29 is a 180° retardation plate angle output terminal, 30 is a 90° retardation plate clear weather stop signal output terminal, and 31 is a 180° retardation plate clear weather stop signal output terminal.

Next, the operation will be explained. The downlink polarized signal received by antenna 1 is sent to group splitter 2.
The downlink system 90° phase difference plate 3, 180° phase difference plate 4, and polarization demultiplexer 5 split the wave into right-handed and left-handed components, and the receiver 12 uses the main polarization as a reference via couplers 10 and 11. Detects cross-polarized components as signals. This cross-polarized component is supplied to the servo control circuit 13 as an error signal, and is controlled and amplified to drive the 90° retardation plate driving mechanism 8 and the 180° retardation plate driving mechanism 9 so that the error signal becomes zero. By controlling the 90° retardation plate and the 180° retardation plate in this manner, the cross-polarized components become zero and can be compensated. Clear weather stop detection circuit 14
is the cross-polarization discrimination degree XPD of the incident wave using the 90° retardation plate angle and the 180° retardation plate angle obtained from terminals 28 and 29.
φ) - 1 (where θ is the 90° retardation plate angle and φ is the 180° retardation plate angle.) If this is larger than a certain reference value, the incident wave XPD is good and the polarization is caused by rain. It is assumed that the deterioration is small, and if the error signal output of the receiver 12 is smaller than a certain reference value, then the compensation is performed.
Assuming that the XPD is good and the compensation operation is complete,
If the incident wave XPD and the compensated XPD are both good, the propagation path is in a clear sky condition and no further compensation is necessary, so the clear sky stop signal is sent to terminals 30 and 31.
The clear weather stop command is outputted to the servo control circuit 13 to stop driving the retardation plates 3 and 4.

On the other hand, the uplink system of the cross-polarization compensator is
It is configured similarly to the downlink system described above using a pilot signal for compensation.

[Problem that the invention seeks to solve]

In conventional cross-polarization compensators, the downlink system and uplink system were configured independently.
In addition to the large number of components and the large size of the equipment, the uplink system does not compensate for its own received waves with the received waves as in the downlink system, so it is necessary to use a compensation pilot to compensate for the transmitted waves. There were problems such as the need for separate signals.

The present invention has been made to solve these problems, and provides a cross-polarization compensator that does not require a separate pilot signal for compensation in the uplink system and can be simplified and miniaturized. With the goal.

Another object of the present invention is to obtain a cross-polarization compensator capable of improving compensation performance in addition to the above-mentioned objective.

[Means for solving problems]

The cross-polarization compensator according to the present invention is capable of adjusting the canting angle of rain and the amount of anisotropic phase shift (DPS), which are the main causes of polarization deterioration due to rain.
Phase Shift) acts on the downlink system and uplink system to estimate the canting angle and DPS of the uplink system from the canting angle and DPS that occur in the downlink system, and from this estimated value, the canting angle and DPS of the uplink system are estimated. This method determines the setting angles of the 90° retardation plate and 180° retardation plate in the system (estimation control method).

Further, the cross-polarization compensation device according to another aspect of the present invention performs the estimation control method of the above invention when it is raining, stops the estimation control method when there is no rain, and performs the estimation control method of the above invention when it is raining, and disables the estimation control method when it is not raining. While keeping the angular relationship of the retardation plate constant, it is gradually changed to a predetermined angle.

[Effect]

In this invention, the amount of cross-polarized waves generated in the uplink system is estimated from the amount of cross-polarized waves generated in the downlink system, and compensation control of the uplink system is performed.
In other words, since the uplink system is made to follow the downlink system with a correlation, there is no need for a pilot signal for compensation in the uplink system.

In addition, in another invention of this invention, it is considered that no cross-polarized waves are generated by the propagation path when there is no rain, and in order to transmit two orthogonal polarized waves of circularly polarized waves, a 90° phase difference plate in the uplink system is used. A 180° retardation plate is set to, for example, 45° and 0°, and the difference between the stopping angle by the estimated control method and the set angle of 45° and 0° is filled without causing XPD deterioration.

[Embodiments of the invention]

FIG. 1 is a block diagram showing a cross-polarization compensator according to an embodiment of the present invention. In the figure, 1 is an antenna, 2 is a group splitter, 3 to 14 are downlink systems, and 15 to 23 are block diagrams. Uplink system components,
3 and 15 are 90° retardation plates, 4 and 16 are 180° retardation plates, 5 and 17 are polarization demultiplexers, 6 and 18 are 90° retardation plate angle detectors, and 7 and 19 are 180° retardation plates. Plate angle detector, 8 and 20 are 90° retardation plate drive mechanism, 9 and 21
is a 180° retardation plate drive mechanism, 10 and 11 are couplers,
12 is a receiver, 13 and 22 are servo control circuits, 1
4 is a clear weather stop detection circuit, 23 is an estimation calculation circuit, 2
4 is a receiving system right rotation terminal, 25 is a receiving system left rotation terminal, 2
6 is a transmission system right rotation terminal, 27 is a transmission system left rotation terminal, 2
8 is a 90° retardation plate angle output terminal, 29 is a 180° retardation plate angle output terminal, 30 is a 90° retardation plate clear sky stop signal output terminal, and 31 is a 180° retardation plate clear sky signal output terminal.

Next, the operation will be explained. First, the downlink system will be described, and this system is similar to the conventional technology. The downlink system polarized signal received by the antenna 1 is split into right-handed and left-handed components by the downlink system 90° retardation plate 3, 180° retardation plate 4 and polarization splitter 5 by the group splitter 2. wave coupler 10,
11, a receiver 12 detects cross-polarized components using the main polarized wave as a reference signal. This cross-polarized component is supplied to the servo control circuit 13 as an error signal, and is controlled and amplified to drive the 90° retardation plate driving mechanism 8 and the 180° retardation plate driving mechanism 9 so that the error signal becomes zero. By controlling the 90° retardation plate and the 180° retardation plate in this manner, the cross-polarized components become zero and can be compensated. The clear weather stop detection circuit 14 is connected to terminal 2.
The incident wave cross-polarization discrimination degree XPD can be calculated using the 90° retardation plate angle and the 180° retardation plate angle obtained from 8 and 29.
XPD=20logtan(θ−2φ)+1/tan(θ−2φ)−1(
However, θ is a 90° retardation plate angle, and φ is a 180° retardation plate angle. ), and if it is larger than a certain reference value, it is assumed that the incident wave XPD is good and polarization degradation due to rain is small, and if the error signal output of the receiver 12 is smaller than a certain reference value, the XPD after compensation is good. Assuming that the compensation operation has been completed, the incident wave
If both XPD and compensated XPD are good,
Since the propagation path no longer needs to be compensated in a clear weather condition, a clear weather stop signal is output to terminals 30 and 31, and a clear weather stop command is given to the servo control circuit 13 to stop driving the phase difference plates 3 and 4. It is.

Next, we will discuss the uplink system. Polarization degradation caused by rain is mainly affected by the canting angle of the rain and DPS (Differential Phase Shift), and if this is known, polarization degradation can be compensated for. Rain events commonly act on uplink and downlink systems, and therefore it is known that the canting angle Θ and DPS(B) have a correlation for uplink and downlink systems. Let this correlation equation be Θ _u =f(Θ _D )...(1) B _u =f(B _D )...(2).

Since the downlink system directly compensates _the received signal, the downlink system canting angle _and DPS are
can be found. Ignoring the polarization characteristics of the satellite and earth station antenna, it can be found using equations (3) and (4).

Θ _D = θ _D +45゜ ……(3) B _D = 90゜−(2θ _D −4φ _D ) ……(4) From this, from the correlation equations (1) and (2), the uplink system canceling Since the angle and DPS can be estimated,
Set values for uplink system 90° retardation plate angle θ _u and 180° retardation plate angle φ _u to compensate for polarization degradation.
It can be obtained by calculating equations (5) and (6).

θ _u = Θ _u +45° ...(5) φ _u = 1/2Θ _u -1/4B _u +90° ...(6) The estimation calculation circuit 23 performs these calculations, and uses the set value as a command. It is supplied to the servo control circuit 22, and in the same circuit 22, the retardation plate angle detector 1
The difference between the actual angle of the retardation plate 8 and 19 is controlled and amplified, and the drive mechanism 20 and 21 moves each retardation plate 1.
5 and 16 to predetermined set values. This compensation method is called an estimated control method.

Furthermore, considering the residual error due to the polarization characteristics of the satellite and earth station antenna, the canting angle and DPS of the downlink system can be found using equations (7) and (8).

Θ _D = τ _D0 −0.5tan ^-1 (F ₁ / F ₂ ) ...(7) B _D = tan ^-1 {tan (2θ _D0 −4φ _D0 ) / sin2 (τ _D0 − Θ _D )
}−tan ^-1 {tan(2θ _D −4φ _D /sin2(τ _D −θ _D )}...
(8) However, τ _D0 = θ _D0 −90° τ _D = θ _D −90° F1=A _D *cos2(τ _D −τ _D0 )−1 F2=A _D *sin2(τ _D −τ _D0 ) A _D = cos (2θ _D −4φ _D ) / cos (2θ _D0 −4φ _D0 ) where θ _D0 is the 90° retardation plate angle in a clear sky with no XPD degradation in the propagation path φ _D0 is a clear sky without XPD degradation in the propagation path of time
180° Retardation Plate Angle From this, the setting angles of the retardation plates 15 and 16 can be determined in the same manner as described above using the correlation equations (1) and (2) and the calculation equations (5) and (6).

The above estimation control method is based on the clear weather stop detection circuit 14.
Using the output of , it may be started automatically when it is determined that it is raining.

By the way, if the output of the clear weather stop detection circuit 14 continues for a certain period, it is determined that there is no rain, and as a result, the uplink system retardation plate drive command is set so that the cross-polarization discrimination degree is lower than the estimated calculation command value. The compensation performance of the uplink system can be improved by changing to a specific angle that is favorable and driving the 90° retardation plate 15 and 180° retardation plate 16 while maintaining a constant angular relationship up to that set angle (recovery). (referred to as steps).

In other words, when there is no rain, the correlation between the uplink system and the downlink system becomes weak, so it is necessary to stop controlling using the above correlation equation. If there is no rain, it is thought that there will be no cross-polarized waves due to the propagation path, and it is sufficient to transmit two orthogonal circularly polarized waves from the earth station antenna, and both retardation plates 1 of the uplink system should be transmitted.
By setting 5 and 16 to 45 degrees and 0 degrees, the required circularly polarized transmission can be achieved and cross polarization compensation can be achieved. However, since the estimated calculation control stop angle and the set angles of 45° and 0° are different, each retardation plate 15, 1
If 6 were driven independently and directly, significant XPD degradation would occur due to the relative relationship of the phase difference plate angles, but this can be avoided by the recovery step.

Accordingly, an embodiment of another invention of the present invention that performs such a recovery step will be described with reference to FIG. In FIG. 2, 1 to 31 are the same as in FIG. 32 is a recovery step command generator that provides a command value when executing the recovery step;
3, a 90° retardation plate 15 and a 180° retardation plate 16 are activated by the clear weather stop signal from the clear weather stop detection circuit 14.
Both are rainless state detection switching circuits that detect that the clear weather stop state has continued for a certain period, cut off the output of the estimation calculation circuit 23, and input the output of the recovery step command generator 32 to the servo control circuit 22. 34 and 35 are angle output terminals of the 90° retardation plate 15 and the 180° retardation plate 16.

Normally, in a rainy state, the downlink system performs a compensation operation using the received pilot signal, and the uplink system performs a compensation operation using a correlation equation with the no-rainfall state detection switching circuit 33 leaning toward the estimation calculation circuit 23 side. When the rain condition disappears, the clear weather stop detection circuit 14 outputs a clear weather stop signal to terminals 30 and 31, and in the downlink system, the servo control circuit 13 stops driving the phase difference plates 3 and 4. Since the downlink system stops, the uplink system also stops at the same time.
The no-rainfall state detection switching circuit 33 has terminals 30 and 31.
The time count starts from the time when both clear weather stop signals are output. The timer settings are such that the clear weather stop signal is not temporary, but responds to gradual changes in the weather. When a no-rain condition is detected in this manner, the circuit 33 switches the command angle signal to the servo control circuit 22 to a command from the recovery step command generator 32.

The recovery step command generator 32 establishes the relationship between the 90° retardation plate angle θ and the 180° retardation plate angle φ as shown in equation (9) in order to avoid XPD degradation due to the combination of retardation plate angles and to transmit circularly polarized waves. θ while always satisfying
This is a command generator that drives φ to 45° and φ to 0°.

θ−2φ=45゜ ...(9) The elliptic polarization coefficient e _P of the transmitted polarized wave due to the retardation plate setting that satisfies the equation (9) is obtained from the equation (10), and from this, e _P =
It can be seen that the wave is completely circularly polarized at 0dB.

e _P = 20log {tan (θ-2φ)} (dB) ...(10) Here, the procedure for command generation is shown in Figure 3. According to the flowchart in the figure, the recovery step command generator 32 reads the angles θ and φ from the terminals 34 and 35 and calculates φ from the calculation of equation (9). This calculated value φ is supplied to the servo control circuit 22 via the no-rainfall state detection switching circuit 33. Servo control circuit 2
2 moves the 180° retardation plate 16 by the calculated value φ via the 180° retardation plate drive mechanism 21. And θ
Move the 90° retardation plate 15 by Δθ in the direction of approaching 45°, and move the 180° retardation plate 16 in the same direction by Δφ=1/2Δθ
Move only. The process ends when θ reaches 45°, and if it does not, move it further by Δθ and repeat the same process.

Here, the drive step widths Δθ and Δφ are selected so that the XPD degradation caused by them can be ignored.

In the above embodiment, the same effect can be obtained even if the 90° retardation plate and the 180° retardation plate are replaced.

Furthermore, although the explanation has been made by setting the uplink system's 90° retardation plate 15 and 180° retardation plate 16 to 45° and 0°, respectively, both angles are not limited to these angles. ) should be satisfied.

Further, by adding the recovery step command generator 32 and the no-rain state detection switching circuit 33 to the downlink system, the present invention can be similarly applied to the downlink system.

〔Effect of the invention〕

As explained above, this invention utilizes the correlation between the canting angle of the downlink system and the uplink system and the DPS, and is configured to perform uplink system compensation control following the downlink system compensation control. Therefore, there is no need for a pilot signal for compensation in the uplink system, which has the effect of simplifying and downsizing the device.

Another invention of the present invention is that the uplink system retardation plate is set to the reference angle in the recovery step when there is no rain, so even under clear weather conditions where the correlation between the downlink system and the uplink system is weak. This has the effect that compensation control can be performed without XPD deterioration.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a cross polarization compensator according to one embodiment of the present invention, FIG. 2 is a block diagram showing a cross polarization compensator according to another embodiment of the present invention, and FIG. 3 is a block diagram showing a cross polarization compensator according to another embodiment of the present invention. FIG. 2 is a flowchart for setting the uplink system retardation plate to a reference angle in the embodiment, and FIG. 4 is a block diagram showing a conventional cross polarization compensator. In the figure, 3 and 15 are 90° retardation plates, 4 and 1
6 is a 180° retardation plate, 6, 7, 18, 19 are retardation plate angle detectors, 8, 9, 20, 21 are retardation plate drive mechanisms, 13, 22 are servo control circuits, 14 is a clear weather stop detection 23 is an estimation calculation circuit, 32 is a recovery step command generator, and 33 is a no-rain state detection switching circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. In a system that compensates for cross-polarized waves generated by an asymmetric medium in a propagation path, such as rain, by using a 90° retardation plate and a 180° retardation plate in a downlink system and an uplink system, The cross polarization components of the received waves obtained through the 90° retardation plate and 180° retardation plate of the link system are detected, and the phase difference between these 90° retardation plates and 180° retardation plate is adjusted so that the detected value becomes zero. Based on the first servo control circuit that rotates the plate and the 90° retardation plate angle and 180° retardation plate angle at this time, the canting angle of the rain acting on the downlink system and the amount of anisotropic phase shift are calculated. An estimation calculation circuit that estimates the canting angle and anisotropic phase shift amount of rainfall acting on the link system, and sets the 90° retardation plate angle and 180° retardation plate angle of the uplink system based on these estimated values. , These settings determine the uplink system through which the transmitted wave passes.
A 90° retardation plate and a second one that rotates the 180° retardation plate.
A cross-polarization compensator comprising a servo control circuit and a servo control circuit. 2 In systems that compensate for cross-polarized waves generated by asymmetric media in the propagation path, such as rain, by using a 90° retardation plate and a 180° retardation plate in the downlink system and uplink system, the 90° retardation plate in the downlink system The first step detects cross-polarized components of the received waves obtained through the retardation plate and the 180° retardation plate, and rotates the 90° retardation plate and the 180° retardation plate so that the detected value becomes zero. Using the servo control circuit of An estimation calculation circuit that estimates the canting angle and the amount of anisotropic phase shift, and sets the uplink system's 90° retardation plate angle and 180° retardation plate angle based on these estimated values, and the transmission based on these set values. Uplink system through which waves pass
A second servo control circuit that rotates the 90° retardation plate and the 180° retardation plate, and a cross-polarization discrimination degree of the incident waves to the 90° retardation plate and the 180° retardation plate of the downlink system are set to a predetermined value. A clear weather stop detection circuit detects that there is no rain when the cross-polarized component of the received wave is below a predetermined value. Recovery in which set values for setting the retardation plate angles of the 180° retardation plate at predetermined angles while keeping the relationship between both angles constant are switched to the set values of the estimation calculation circuit and output to the second servo control circuit. A cross-polarization compensator comprising a step command generator.