EP1485967B1 - Method and device for tracking an antenna - Google Patents

Abstract

The invention relates to an improved method and to a corresponding device for tracking an antenna located on or in a moving object, to a transmitter, particularly to a satellite. The invention is characterized, among other things, by the following features: both main beam directions (K1, K2) or major lobes (HK, VK) of both received orthogonal polarizations (H, V) each have a squint angle ( alpha ) that diverges with regard to one another, and; the orientation and tracking of the antenna (3) for attaining a maximum receive level of the respective currently received polarization (H, V) ensues according to a received signal with regard to the additional polarization of the received signal level that, due to the squinting orientation, is lower and produces a high level variation.

Description

The invention relates to a method and a device for tracking an antenna to receive orthogonal polarized transmission signals according to the preamble of the claim 1 or 9.

As is known, satellite antennas have to receive according to programs broadcast via satellites be aligned exactly to a satellite. This is basically possible in vehicles even if this are in parked position. Problems exist however, if, for example, satellite programs to be received in moving objects, ie while a car or bus ride, a train ride on Ships or in airplanes.

The reception of satellite signals in such moving Objects are made more difficult by the fact that the receiving antennas because of the small half width exactly on the satellite must be aligned. This can be vehicles with Angular velocities in the azimuth plane of more than Move 30 ° / sec and more. This requires high demands to the tracking properties of an antenna system the antenna especially in azimuthal direction changes of the object always in the optimal reception.

Basically, there is already a tracking system for tracking a satellite antenna to a geostationary satellite position become known on moving objects. It is via a corresponding motor drive the satellite antenna in a steady oscillating motion held and the received signal level evaluated. If there is a reduction in the signal level, the Antenna returned again until after a rise in the Signal level again determine a fall in the signal level is. In other words, you leave that Main beam direction or main lobe of the receiving system the satellite antenna around the theoretical optimum value permanently commute to find out about the optimal information To get alignment. Such a system has but several disadvantages. Disadvantageous for a that by the permanent drive and the permanent Adjustment of the satellite antenna by the mentioned Pendulum movements of the wear of the entire system considerably is. In addition, the cost expense is also not inconsiderable. Above all, the disadvantage is that the signal level of the satellite never optimally exploited can be, because by the pendulum motion, the main radiation direction or main lobe of the antenna for optimal alignment must be brought out, leading to the undesirable Drop of the signal level leads.

In addition, from DE 195 48 206 A1 a further device for receiving a satellite signal become known, for example, on trucks can be installed. When cornering, the Determination of an azimuthal angle deviation between the Direction of arrival of the satellite signal and the direction of reception the antenna by measuring the strength of the received Satellite signal. The antenna will also, as in the aforementioned prior art, after adjustment their elevation angle around their vertical Axis pivoted back and forth until the received Satellite signal reaches a maximum value. Does that happen? received satellite signal again, because the antenna for example, as a result of cornering of the land vehicle is turned away from the receiving direction of the satellite, the antenna is again pivoted about its vertical axis, until the received satellite signal again reaches a maximum value. Because with this azimuthal tracking the antenna at a drop in the received Satellite signal does not determine which Direction the antenna must be swiveled, this must be always be tried by swinging back and forth. If the received satellite signal continues to fall, that was Pivoting direction wrong.

Also the direction of the azimuthal tracking of the antenna To be able to determine, it is preferably proposed that Antenna at a small angle about its vertical axis pivot after the direction of incidence of the satellite signal has been found. This azimuthal angle deviation the receiving direction of the antenna from the direction of incidence the satellite signal can be chosen so small be that the strength of the received satellite signal is above a minimum value, which is still one Image and sound reception should ensure. By this arrangement So the antenna will never be in the optimal reception direction operated. This raises problems especially when the vehicle is in a receiving area, in which the satellite signal from home already weaker.

The object of the present invention is therefore based on an improved from the last-mentioned prior art Tracking system especially for satellites with dual polarized transmit signals to create so before In particular, a satellite antenna, i. especially one Flat antenna to achieve a high reception / signal level optimally aligned to a satellite.

The object is with respect to the method according to the in claim 1 and with respect to the device accordingly solved the features specified in claim 9. advantageous Embodiments of the invention are in the subclaims specified.

Compared to the last mentioned generic class the technique, it is possible according to the invention, a change in direction e.g. of a vehicle with respect to a targeted Satellites safe to detect the antenna system targeted and thus drive-friendly actually to track to a maximum reception level.

The invention is based on the following preliminary considerations on.

To make the most of the available frequency resources, Satellites transmit orthogonally polarized signals. A Satellite receiving antenna is capable of doing this orthogonal polarizations of a given frequency band (often a lower or upper frequency band) receive. For linear polarizations one calls the both orthogonal polarizations with horizontal, though the E vector is horizontal to the earth, i. parallel to the horizon runs. From a vertical polarization is spoken when the E vector of the polarized electromagnetic Wave perpendicular to the earth, i. perpendicular to Horizon passes. At a circular polarization are the two orthogonal polarizations circularly clockwise or counter-clockwise.

According to an antenna is now constructed so that the main beam directions, i. the main lobes for the respective polarization differ from each other. With in other words, the antenna is left to e.g. in the azimuth plane squinting at a defined angle, i. that the Axes of the main lobes of the two orthogonal polarizations in the azimuth plane from each other by a defined Deviate angle. This allows, for example, that the main beam direction or the main lobe of the antenna or the feed system with respect to the H-polarization the desired satellite is aligned and in contrast the second polarization, in this case the V-polarization corresponding signals from the same satellite receives, but in the steeper flank area of the Main lobe. A deviation of the antenna alignment can now easily and accurately detected, since already a slight deviation with respect to an optimal Alignment of the antenna to the satellite with respect to the second polarization to a much greater signal level drop or a much stronger signal level rise leads, as this for the optimally aligned Polarization could be detected.

Should each receive programs of the other polarization so this other polarization is shown in the picture Example the main beam direction of the antenna with respect to the V-polarized electromagnetic waves, optimally received, i. aligned to the desired satellite, whereas the second polarization, i. the H-polarization now for detecting a deviation of Alignment of the antenna and a corresponding tracking is used.

It has now been shown that a squint angle of for example, 0.2 ° - 2.0 °, preferably 0.4 ° - 1.0 ° full is sufficient. Because optimal conditions are always then reached when level differences of the detected polarization per angle change are as large as possible, thereby but the absolute reception level is not too small, so that the level difference is easy to detect. With In other words, so the squinting angle should be set be that - if the antenna with respect to the one actively received polarization is optimally aligned - the second to detect alignment and tracking received signal levels of the second polarization, for example has a signal level difference of 4 to 5 dB. Will the antenna then out of their while driving pivoted out optimal position, so can by means of detected polarization a level difference of, for example 2 dB with respect to the squinting polarization be well measured, with such level differences with respect the detected polarization to no appreciable Level losses with respect to the other received Polarization leads, whose main beam direction on the Satellite should be optimally aligned.

It is particularly advantageous according to the inventive solution also that the direction of the readjustment recognizable is. A level increase of the detected received signal one polarization indicates that the antenna from the non-squint position toward the detected one squinting position must be adjusted. there even the angle range can be adjusted by the level difference determine. From the level deviation can ultimately even derived an adjustment angle or a specific one Adjustment angle assigned to a specific level deviation become.

Conversely, in case of a deviation of the detected control level derived to lower values, that the antenna moves towards non-squinting polarization must become.

From the described facts it appears that the antenna can easily readjust without the Reception is impaired. In addition, the post-regulations only required if a misalignment actually to correct. As long as the detected signal the polarization evaluated for tracking no Signal level change, the entire system can in Rest remain, so that no motor drive for the tracking must be activated. This will be the total load of the rotationally driven mechanics significantly minimized in the prior art.

For example, flat antennas with very large differences in the dimensions for the azimuth direction (large Dimension) and the elevation direction (small dimension) and thus very different half widths in Azimuth (small half width) and elevation direction (large half width), it is sufficient that in normal driving a readjustment only in Azimutrichtung takes place, since by the large half width in the elevation direction, a slope or a slope to 8% leads to no noticeable loss of reception.

Preferably, however, an alignment or readjustment in the elevation direction also at greater intervals be made in the system according to the invention.

If a GPS receiver is also available, deviations can occur the elevation basic settings and the necessary information is delivered to the tracking system become. An evaluation of the level differences can be very simply by measuring the AGC (Antenna Gain Control) of the Frontends are carried out. A downstream AD converter can then provide the appropriate information to the Microprocessor deliver.

Figur 1:

eine schematische Darstellung eines Satelliten sowie einer Satelliten-Empfangsantenne;

Figur 2:

eine schematische Darstellung des erfindungsgemäßen Trackingsystems mit einer Auswert-, Kontroll- und/oder Steuerungseinrichtung;

Figur 3:

ein Diagramm bezüglich der schielenden Ausrichtung der beiden Hauptstrahlrichtungen der Antenne zur Verdeutlichung des Empfangs-Signalpegels;

Figur 4:

eine schematische perspektivische Darstellung einer Flachantenne mit unterschiedlicher Erstreckung in Horizontal- und Vertikalrichtung;

Figur 5:

ein Azimutdiagramm bezüglich der in Figur 3 wiedergegebenen Flachantenne; und

Figur 6:

ein Elevationsdiagramm.

The invention will be explained in more detail using an exemplary embodiment with reference to the drawings. In detail:

FIG. 1:

a schematic representation of a satellite and a satellite receiving antenna;

FIG. 2:

a schematic representation of the tracking system according to the invention with an evaluation, control and / or control device;

FIG. 3:

a diagram with respect to the squinting orientation of the two main beam directions of the antenna to illustrate the reception signal level;

FIG. 4:

a schematic perspective view of a flat antenna with different extension in the horizontal and vertical directions;

FIG. 5:

an azimuth diagram with respect to the reproduced in Figure 3 flat antenna; and

FIG. 6:

an elevation diagram.

In Figure 1 is a schematic representation of a geostationary Satellite 1 reproduced. About this satellite the programs are orthogonal to each other over at least two sent stationary polarization planes.

These two orthogonal polarizations can be over a Antenna 3, in the embodiment shown, a satellite antenna in the form of a flat antenna 3 'are received.

This flat antenna 3 'is, for example, on or in provided a moving object, such as a Motor vehicle, bus, ship or the like.

During the trip, so the antenna 3 must always track so that ensures optimal program reception becomes.

In the illustrated embodiment, the antenna 3 with a tracking system 7 explained below (FIG. 2), So in the broadest sense with an evaluation and succession control device 7, about which a drive device 9 for alignment of the antenna 3 driven can be. This drive device 9 comprises at least a vertical axis of rotation 11 around which by means of the evaluation and control device, so ultimately by means of the tracking system 7 and the corresponding drive device 9 ', a tracking of the antenna 3 in Azimuth direction is enabled. In addition, too preferably a horizontal axis of rotation 13 is provided, to the antenna 3 also by means of another drive device 9 "in the elevation direction can.

The antenna 3 including an associated feed system is constructed so that the main beam directions of the two polarizations differ, with others Words so the main radiation direction K1 for the horizontal Polarization with respect to the main radiation direction K2 for the vertical polarization V at a defined angle α to each other. This can be, for example in the case of a flat antenna by appropriate measures in realize the information networks.

So one leaves so far the flat antenna in the azimuth plane by a defined angle α, i. e. the Axes K1 and K2 of the main lobes HK and VK of the two orthogonal polarizations deviate in the azimuth plane of each other around the mentioned defined angle α, so can e.g. the main lobe HK of H-polarization to the desired Satellites 1 are aligned exactly, whereas the main lobe VK of the V polarization of the same Satellite receives the appropriate signals, however not in the range of the largest signal level, but in the steeper flank area 15 of the main lobe VK. This opens the possibility of deviations of the antenna alignment very easy and accurate to detect. This should be based on Figure 3 are explained in more detail, wherein the reference to FIG 3 explained main lobes HK and VK in the schematic perspective view in Figure 1 with respect to the Planar antenna are shown schematically.

In the example according to the diagram of Figure 3 will of it assumed that, for example, on the moving object Programs are to be received by the satellite 1 emitted via the horizontal polarization become. Therefore, the horizontal polarization H of the Antenna 3 or the associated feed system at optimum Reception be aligned, so exactly to the receive direction of the satellite to a high input signal level to realize. This is shown in Figure 3 on the arrow 6 indicates the exact position of the satellite 1, by means of which, for example, the H-polarization with maximum signal level to be received. This is in Figure 3 by means of the solid line 17 of the received signal level profile the respectively actively received polarization, in the illustrated embodiment of the H-polarization, reproduced, wherein the satellite antenna 3 and thus this receive signal level profile 17 with its main lobe HK and thus with its main beam direction K1 exactly is aligned to the satellite 1, so for example in terms of H-polarization, the maximum signal level 17 'can be received.

In contrast, now the main radiation direction K2 for the main lobe VK for the vertical polarization V in a previously defined angle α of about 0.6 ° easily squinting to the main beam direction K1 of the main lobe to Reception of the other polarization aligned. Of the Receive signal level profile 19 of the antenna 3 and the associated feed system for receiving the vertical Polarizations V is shown in dashed lines in Figure 3 and is according to the squint angle α offset from the active receive signal level profile 17. In the illustrated embodiment according to Figure 3 is at optimal or maximum received signal level 17 'with respect to the active received Polarization contrast, for the second polarization V only a signal level 19 'received on the Flank 15 of the signal level curve 19 still in the upper range lies.

In the example chosen, the result is therefore for the vertical Polarization V a level difference of about -5 dB.

Would now the vehicle with the aforementioned antenna. 3 while driving make a turn, in which the receive signal levels 17 and 19 in the diagram 3 after right, based on the optimum direction of reception 21, drift away This would already be the case with a shift from 0.1 ° to 0.2 ° results in the level range with respect to the received vertical polarization over -6 dB would fall off. This waste can be clear and be measured quickly. This waste can then be in the Tracking system 7 including the evaluation and control device 7 'are used to about the corresponding drive device 9 'to the vertical Rotate axis 11 so that the main lobe HK for the horizontal polarization H of the antenna or the feed system with their main beam direction again congruent comes to lie to the optimum direction of reception 6. So while through the detected and the tracking serving vertical input receive signal 19 ' Polarization a strong signal drop quickly detectable has this in the listed angle range for that received active horizontal polarization signal none relevant influence, so that actively received about this Programs with virtually consistent quality and almost constant maximum signal level are received could.

Would while driving the moving object cornering would be made in a different direction, so would this, for example, cause the two receive signal level traces 17 and 19 in the diagram according to FIG. 3 would drift away to the left. This would lead to an increase the received signal level 19 'with respect to the vertical Polarizations lead, so here again very much quickly via the tracking system including the evaluation and control device, the drive device 9 ' could be controlled so that the antenna 3 in opposite Rotation movement is tracked.

The entire setting is thus advantageously so chosen that level differences of the detected polarization per angle change are large, the absolute reception level but not too small, hence the level difference still easy to detect. For example, how mentioned, the squint angle α between the two received Polarizations chosen to be approximately one Level difference of about 5 dB between the two polarizations results, this leads to a level range of about -2.5 to -6.5 dB or, for example, -3 to -7 dB well measurable level differences of about 2 dB. With others Words already lead to slight deviations of the satellite antenna from their optimal orientation to the concerned one Satellites too fast detectable and sufficient large signal changes with respect to the squinting Polarization, that is, in an area where still no significant level losses of the active polarization plane are detectable, the main beam direction on the satellite to receive the one you want Program is aligned.

Using flat antennas with very large differences in the dimensions for the azimuth direction (with one possible large dimension) and the elevation direction (with the smallest possible dimension) and thus very different Halfwidths in azimuth direction (small Half width) and in the elevation direction (large half width), so must in normal operation only in azimuth direction be readjusted, since large half widths in Elevation direction cause that on gradients or Gradients of up to 8% practically no noticeable loss of reception determine is.

With reference to Figure 4, such an antenna is in perspective Illustration indicated, including a three-dimensional representation of the main radiation direction or main lobe (partially reproduced in section).

From this representation as well as in the further in FIG. 5 reproduced azimuth diagram and the reproduced in Figure 6 Elevation diagram yields the small one Half width in azimuth direction (in which the above explained, if necessary, each carried out readjustment or tracking the antenna carried out on the satellite becomes) and the comparatively large half width in the elevation direction, where it usually barely to a relevant signal level deterioration comes.

Regardless, it is recommended in the elevation direction to carry out a follow-up orientation. This before especially because of different reception locations different basic settings of the elevation directions required are. This correction can be done in temporal Distances, e.g. every half hour by realignment in Elevation direction take place. This can, for example, the Orientation of the antenna in elevation changed so be that the level is due to misalignment by e.g. 2 dB, then the antenna in opposite Direction, so on the opposite side to adjust the main lobe until again the same Receiving level is set. Subsequently, the satellite antenna then to the middle between the two settings be adjusted. This process is only very rarely necessary and does not burden the system unnecessary adjustments.

A still improved solution offers itself then if, in addition, a location system, for example exists in the form of a GPS receiver. deviations the elevation basic settings for the respective receiving location can then be passed through this GPS receiver easily find out the necessary information then be delivered to the tracking system. A corresponding readjustment as described above is then unnecessary.

An evaluation of the level differences can then be very simple by measuring the AGC, ie the Antenna Gain Control Signals are carried through the frontend. A downstream one AD converter can provide the appropriate information a microprocessor as part of the tracking system, i.e. as part of the evaluation and control device.

Claims (16)

1. Method for slaving of an antenna, which is located on or in a moving object, to a transmitter, in particular to a satellite, which emits signals in two polarizations which are aligned orthogonally with respect to one another, characterized by the following features:

   antennas are used whose two main beam directions (K1, K2) or main lobes (HK, VK) have a divergent squint angle (α) with respect to one another with reference to the two received orthogonal polarizations (H, V),

   in order to receive programmes which are transmitted via the horizontal polarization (H), the antenna (3) is slaved as a function of the reception signal level (19'), and/or the reception signal level differences (19') of the further detected vertical polarization (V), and

   in order to receive programmes which are transmitted via the vertical polarization (V), the antenna (3) is aligned and slaved as a function of the reception signal level (17') and/or the reception signal level differences (17') of the further detected horizontal polarization (H).
2. Method according to Claim 1, characterized in that an antenna is used with a squint angle (α) between the two main lobes (HK, VK) for reception of the two polarizations (H, V), such that the reception signal level (19') which is used for detection for the slaving of the antenna for the one polarization is about 2 to 8 dB, and preferably about 4 to 5 dB less, than the reception signal level (17') of the other polarization (H, V) which is slaved for optimum reception, of the antenna (3).
3. Method according to Claim 1 or 2, characterized in that a squint angle (α) is used between the two polarizations (H, V) such that the received signal level (17', 19') of the polarization (V, H) which is used for detection for the slaving of the antenna (3) is in the flank area (15) of the main lobe (HK or VK).
4. Method according to one of Claims 1 to 3, characterized in that, when the reception signal level (17', 19') which is used for detection of the squint polarization rises, the antenna (3) is moved such that the main beam direction (K1, K2) or main lobe (HK, VK) of the polarization (H, V) which is to be slaved and is used for reception of a programme is moved in the direction of the squint polarization (H, V) which is used for detection.
5. Method according to one of Claims 1 to 4, characterized in that, when the reception signal level (17', 19') which is used for detection of the squint polarization falls, the antenna (3) is moved such that the main beam direction or main lobe of the polarization (H, V) which is to be slaved and is used for reception of a programme is moved away from the squint polarization (H, V) which is used for detection.
6. Method according to one of Claims 1 to 5, characterized in that a flat antenna (3, 3') is used.
7. Method according to Claim 6, characterized in that a flat antenna (3, 3') is used with a summation network which is set such that the main directions (K1, K2) or main lobes (HK, VK) for reception of the two orthogonal polarizations (H, V) are aligned at a defined squint angle (α) with respect to one another.
8. Method according to one of Claims 1 to 7, characterized in that a flat antenna (3, 3') is used, whose azimuth extent with respect to the elevation extent is of such a size that it has a longitudinal extent in the azimuth direction which is at least three times as great, and preferably four times as great, as in the elevation direction.
9. Apparatus for slaving an antenna, which is located on or in a moving object, to a transmitter, in particular to a satellite, which transmits signals in two polarizations which are aligned orthogonally with respect to one another, having an evaluation, monitoring and/or control device (7) for slaving of the antenna (3) about at least one axis in the azimuth direction, characterized by the following further features:

   the antenna (3, 3') and/or the feed system are/is designed such that the two main beam directions (K1, K2) or main lobes (HK, VK) of the two received orthogonal polarizations (H, V) run such that they diverge with respect to one another at a squint angle (α),

   the evaluation, monitoring and/or control device (7) is used to evaluate the signal level (19', 17') and/or the respective main lobe (VK or HK) which is set to a squint angle with respect to the associated, received polarization (V or H), and the resultant signal level change, such that the respective other polarization (H or V) via which a respectively currently desired programme is being received has a higher signal level (17' or 19'), preferably a maximum signal level (17' or 19'), with respect to the signal reception level (19' or 17') of the polarization which is set to a squint angle.
10. Apparatus according to Claim 9, characterized in that the squint angle (α) between the two polarizations (H, V) or between the main beam directions (K1, K2) and/or the two main lobes (HK, VK) is provided such that the reception signal level (19', 17') which is used for detection for the slaving of the antenna (3) is about 2 to 8 dB lower, and preferably about 4 to 5 dB lower, than the reception signal level (17', 19') of the main lobe (HK or VK), which is slaved to optimum reception, of the antenna (3).
11. Apparatus according to Claim 9 or 10, characterized in that the squint angle (α) between the two polarizations (H, V) or the two main beam directions (K1, K2) of the main lobes (HK, VK) is provided such that the received signal level (17' or 19') of the polarization which is used for detection for the slaving of the antenna (3) is in the flank area (15) of the main lobe (VK, HK).
12. Apparatus according to one of Claims 9 to 11, characterized in that, when the reception signal level (19' or 17') of the polarization which is set with a squint angle and is used for detection rises, the antenna (3) can be moved such that the main beam direction (K1 or K2) which is to be slaved and is used for reception of a programme of a main lobe (HK or VK) can be moved in the direction of the squint main beam direction (K2 or K1), which is used for detection, of the main lobe (VK or HK) of the further polarization (V, H).
13. Apparatus according to one of Claims 9 to 12, characterized in that, when the reception signal level (19' or 17') of the main beam direction (K2 or K1) of the main lobe (VK, HK) used for detection falls, the antenna (3) can be moved such that the main beam direction (K1 or K2), which is to be slaved and is used for reception of a programme, of the associated main lobe (HK or VK) can be moved away from the squint main lobe (VK or HK), which is used for detection, or from the associated main beam direction (K2 or K1).
14. Apparatus according to one of Claims 9 to 13, characterized in that the antenna (3) is in the form of a flat antenna (3').
15. Apparatus according to one of Claims 9 to 14, characterized in that the antenna (3) is, in particular, in the form of a flat antenna (3') and is equipped with a summation network which is set such that the main lobes (HK, VK) or their corresponding main beam directions (K1, K2) are aligned at a defined squint angle (α) with respect to each other for reception of the two polarizations (H, V).
16. Apparatus according to one of Claims 9 to 15, characterized in that the antenna (3) is, in particular, in the form of a flat antenna (3'), such that its azimuth extent is designed with respect to the elevation extent, that is to say it has a longitudinal extent in the azimuth direction which is at least three times as great, and preferably four times as great, as in the elevation direction.

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