JPH0219657B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention automatically compensates for cross-polarization caused by asymmetric media such as rainfall in high-frequency signals propagating in circularly or linearly polarized waves. It is related to the device.

[Conventional technology]

When two circularly polarized waves with opposite rotations pass through a propagation path space with an asymmetrical factor such as rain and are received by an antenna, interference occurs between these two polarized waves, but at around 90 degrees. Retardation plate, 180° retardation plate,
Using a tracking receiver and servomechanism, the incoming polarization can be automatically converted into two orthogonal linear polarizations, which can improve this interference.
FIG. 4 shows an example of a circuit for converting incident polarized waves into linearly polarized waves in the receiving system. In FIG. 4, the polarized wave incident on the antenna 1 becomes an elliptically polarized wave due to rain, etc., and after passing through the 90° retardation plate 2 and the 180° retardation plate 3, the x-axis component and the y-axis component at the terminal 14. The axial component is separated by a polarization splitter 4 and the respective components are output to terminals 19 and 20. Further, some of these components are supplied to a tracking receiver 9 by couplers 5 and 8. If it is desired to make the interference component output to the terminal 20 zero at this time and obtain a linearly polarized wave output only to the terminal 19, the receiver input terminal 15 may be used as the reference input and 16 as the error input. Tracking receiver 9
detects the in-phase component and quadrature component of the error signal with respect to the reference signal, outputs the in-phase component having error amplitude information to terminal 17, and outputs the quadrature component having error phase information to terminal 18. When the drive mechanisms 6 and 7 are driven through the servo amplifier circuits 10 and 11 so that the error component becomes zero, the 90° retardation plate 2 and the 180° retardation plate 3 connected to the drive mechanism rotate. When the stable position is reached, the interference component at the terminal 20 disappears. This is because the 90° retardation plate 2 converts the incident circularly polarized wave at the terminal 12 into a linearly polarized wave, and the 180° retardation plate 3
This is to rotate the converted linearly polarized wave at the terminal 13 at the terminal 14 so that it coincides with the x-axis.

This principle can be similarly applied to a transmission system, the configuration of which is shown in FIG.

In FIG. 5, 1 to 20 are the same as in FIG. 4. 21 is a group splitter, 22 is a 90° phase difference plate, 23
is a 180° phase difference plate, 24 is a polarization splitter, 25 and 26 are drive mechanisms, and 27 and 28 are servo amplifier circuits.
It has the same functions as the receiving system. 32 to 44 are terminals. In the transmission system, when a carrier signal is inputted as a normal polarized wave to the terminal 43 and a counterclockwise polarized wave signal subjected to carrier suppression modulation is inputted to the terminal 44 and transmitted to the satellite from the antenna 1, rain etc. on the propagation path are input. Due to the asymmetry factor of
It is received by antenna 1 shown in the figure. In this case, the interference in the uplink of the transmission system is obtained at the terminal 36 as a composite signal in which the interference component is superimposed on the carrier wave as a sideband. When this is detected by a so-called single-channel tracking receiver 30, an in-phase component with error amplitude information is output to the terminal 38, and a quadrature component with error phase information is output to the terminal 37, just like the receiving system. . Therefore, if these error signals drive the 90° retardation plate 22 and the 180° retardation plate 23 and the error is made zero, the interference component of the transmitted signal from the earth station received by the satellite becomes zero. , cross-polarization compensation is possible. This is called the pilot control method. An estimation control method is known as a cross-polarization compensation method for a transmission system. This is the downlink cross-polarization discrimination
This method takes advantage of the fact that there is a correlation between XPD deterioration and uplink XPD deterioration.
The estimation calculation circuit 31 calculates the set angles of the 90° retardation plate 2 and 180° retardation plate 3, and estimates the XPD deterioration state of the transmission system based on this. 22 and the setting angle of the 180° phase difference plate 23. The estimation calculation method at this time is to calculate the canting angle of the rain acting on the downlink system and the amount of anisotropic phase shift (DPS = Differential Phase
Shift) and estimate the canting angle and DPS of the rain acting on the uplink system from this calculated value (the canting angle of the rain and DPS have a correlation for the downlink system and the uplink system.)
Then, from this estimated value, the setting angles of the 90° retardation plate 22 and the 180° retardation plate 23 are determined. Error signals between the current actual setting angle and the above calculation command angle from both phase plates 22 and 23 are output to terminals 41 and 42, and this is controlled and amplified by servo amplifiers 27 and 28 to produce a 90° phase plate 22. By driving the phase difference plate 23 by 180°, cross-polarization compensation of the transmission system can be performed. These two control methods may be used together when increasing the reliability of the system. 29 is a switch for switching between the pilot control method and the estimated control method, and the terminal 3
Error signals at terminals 7 and 38 and terminals 39 and 40 are switched respectively.

[Problem that the invention seeks to solve]

Conventional cross-polarization compensators are configured as described above, and can obtain good compensation performance in both the pilot method and the estimation control method. However, when switching from the pilot method to the estimation control method, the earth station Due to the elliptical polarization characteristics of the antenna and the precision of the XPD correlation, the retardation plate setting angle during pilot control and the setting angle during estimation control do not necessarily match, so there may be large movements during switching. At this time, the 90° phase difference plate 22
Since the 180° phase difference plate 23 and the 90° phase difference plate 23 move independently on the shortest course as shown in FIG. Due to the relative angular relationship of the plates 23, large XPD degradation occurs as shown in the example of FIG.

This invention was made to solve the above-mentioned problems, and it is possible to control the relative relationship between the two retardation plates at the time of switching, thereby minimizing XPD deterioration during driving. The purpose is to obtain a cross-polarization compensator.

[Means for solving problems]

The cross-polarization compensator according to the present invention adds a switching drive control circuit to the output of the estimation calculation circuit, and at the time of switching, does not directly drive the uplink system retardation plate using the setting value of the estimation calculation. While gradually moving one retardation plate of the uplink system to this calculation setting value, calculate the optimal angle of the other retardation plate so that the XPD degradation at that time is minimized, and drive using this as the command value. This is how it was done.

[Effect]

In this invention, when switching the control method, the switching drive control circuit determines the relative relationship between the two retardation plates based on the polarization state immediately before switching so that XPD degradation is minimized. Very accurate switching control becomes possible.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, 1 to 44 are the same as those shown in FIG.

54 is a switching drive control circuit, in which the actual setting angles of the 180° retardation plate 22 and 90° retardation plate 23 are input from the estimation calculation circuit 31 to terminals 45 and 46, respectively, and the polarization is input to terminals 47 and 48. As the state, circular polarization ratio and tilt angle information are input. Terminals 53, 5
A switching signal between the pilot control method and the estimated control method is input to 2 and 51. Switching drive control circuit 5
4, when switching to the estimation control method by the switching signal at the terminal 51, first, the circular polarization ratio and the tilt angle information at the terminals 47 and 48 are used to set the phase difference between the 90° phase difference plate 22 and the 180° phase difference, which minimizes the XPD deterioration. The set angle of the plate 23 is calculated, and the error from the actual set angle of the terminals 45 and 46 is outputted to the terminals 49 and 50. As a result, both retardation plates 2
2 and 23 are driven and moved to the calculation set value of the estimation control. When the calculation set value is reached, the control shifts to the original estimation calculation control, and the error angle signals at the terminals 41 and 42 are outputted as they are to the terminals 49 and 50 to control the retardation plate.

In Fig. 1, the electric fields of the X-axis and Y-axis components of the transmitted polarized wave transmitted from the terminal 33 are expressed as Ex〓 and Ey〓, respectively.
Then, these are expressed by equation (1).

Ex=R+Le ^j2 〓 Ey=j(R−Le ^j2 〓(1) where R: Right-handed component of transmission polarization L: Left-handed component of transmission polarization 2β: Relative phase difference between R and L Rainfall on propagation path, etc. With respect to the polarization state of the transmitted polarized wave due to the influence of
It is determined by the second equation.

However, θ: 90° Retardation plate setting angle Ψ: 180° Retardation plate setting angle Here, for example, if during pilot control, if XPD deterioration due to rain etc. is completely compensated for, then the polarization state at that time will be Retardation plates 22, 23
From the angle of , it can be found as follows.

Assuming that the polarization state does not change during driving when the control method is switched (switching occurs in a short time, even if the polarization state changes, it will be gradual compared to the switching time). As shown in FIG.
While driving the 180° retardation plate 23 little by little,
It is sufficient to perform calculations and control so that the XPD given by equation (2) is minimized. The angle of the 180° retardation plate 23 that satisfies this can be found using equation (4).

Ψ=-1/4tan ^-1 1-(R ² /L)/2(R/L)cos2
(β−θ)+θ/2
...(4) In this way, by inputting (R/L) and β determined by equation (3) and gradually bringing θ closer to the estimated calculation command value, Ψ for each θ value is obtained. Then, when θ matches the estimated calculation setting value, Ψ is also replaced with the estimated calculation setting value, and driving is completed, and thereafter compensation control can be performed using the original estimation control method.
In this case, the XPD during driving will not be worse than the XPD at the estimated calculation setting value.

As an example, FIG. 3 shows the movement of each retardation plate in the uplink system and changes in XPD when switching from pilot control to estimation control. This shows that XPD deterioration is kept to a minimum.

In addition, in the above embodiment, switching from pilot control to estimation control was explained, but there may be cases where the calculation setting angle changes when driving is temporarily stopped during estimation control and restarted, or if necessary. The switching drive control circuit of the above embodiment also produces the same effect even in the case where the drive is performed at a predetermined set angle.

In this case, since the calculation setting angle after switching indicates the polarization state due to the propagation path, (R/L) and β input to equation (4) are the calculation setting angle as shown in (3). You can use the numerical value obtained by inputting it into the formula.

Furthermore, similar effects can be obtained by replacing the 90° and 180° retardation plates in the above embodiments. Furthermore, in the above embodiment, the two retardation plates are 90° retardation plates.
Although the explanation has been made using a 180° retardation plate, it is also possible to use two 90° retardation plates.

〔Effect of the invention〕

As described above, the cross-polarization compensator of the present invention estimates the angle of two retardation plates in the uplink system from the angles of the two retardation plates in the downlink system and rotates them to a set value. By gradually moving one retardation plate up to This has the effect of preventing deterioration from occurring.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the cross-polarization compensator according to the present invention, FIG. 2 is a diagram illustrating the switching operation from pilot control to estimation control in the embodiment shown in FIG. 1, and FIG. 1 is a time chart showing changes in the phase difference plate and XPD when switching from pilot control to estimation control in the embodiment shown in FIG. 1, and FIG. 4 is a block diagram showing the downlink system of a conventional cross polarization compensator. , FIG. 5 is a block diagram showing a conventional cross-polarization compensator, FIG. 6 is a diagram explaining the switching operation from pilot control to estimation control in the conventional device, and FIG. 7 is a diagram illustrating the switching operation from pilot control to estimation control in the conventional device. This is a time chart showing the deterioration of XPD when switching. In the figure, 2 and 22 are 90° retardation plates;
3 is a 180° phase difference plate, 6, 7, 25, 26 are drive mechanisms, 9, 30 are tracking receivers, 10, 11, 27,
28 is a servo amplifier circuit, 31 is an estimation calculation circuit, 5
4 is a switching drive control circuit. In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. In a device that compensates for cross-polarization caused in a high-frequency signal by an asymmetric medium in a propagation path such as rain, by using two retardation plates in a downlink system and an uplink system, respectively, a first servo control means for detecting a cross-polarized component of a received wave obtained via both phase difference plates of a downlink system and rotating both phase difference plates so that the detected value becomes zero; An estimation calculation circuit that estimates and calculates the set angle of both retardation plates of the uplink system through which the transmitted wave passes from both retardation plate angles, and a retardation plate angle of one of the uplink systems that gradually approaches the above set angle. A switching drive control circuit that derives the other retardation plate angle of the uplink system from the circular polarization ratio and tilt angle so that the deterioration of the cross-polarized wave discrimination degree of the above-mentioned transmitted wave is minimized; A cross-polarization compensator comprising: second servo control means for rotating both retardation plates of an uplink system with a retardation plate angle obtained from a switching drive control circuit. 2. The cross-polarization compensation device according to claim 1, wherein the two retardation plates in the downlink system and uplink system are a 90° retardation plate and a 180° retardation plate.