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WO2022162294A1 - Method and system for controlling an antenna in a satellite communication system - Google Patents

Method and system for controlling an antenna in a satellite communication system Download PDF

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Publication number
WO2022162294A1
WO2022162294A1 PCT/FR2022/050094 FR2022050094W WO2022162294A1 WO 2022162294 A1 WO2022162294 A1 WO 2022162294A1 FR 2022050094 W FR2022050094 W FR 2022050094W WO 2022162294 A1 WO2022162294 A1 WO 2022162294A1
Authority
WO
WIPO (PCT)
Prior art keywords
terminal
antenna
ground station
sight
depointing
Prior art date
Application number
PCT/FR2022/050094
Other languages
French (fr)
Inventor
François VARIERAS
Original Assignee
Safran Data Systems
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Safran Data Systems filed Critical Safran Data Systems
Publication of WO2022162294A1 publication Critical patent/WO2022162294A1/en

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/1851—Systems using a satellite or space-based relay
    • H04B7/18519—Operations control, administration or maintenance
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/185—Space-based or airborne stations; Stations for satellite systems
    • H04B7/1851—Systems using a satellite or space-based relay

Definitions

  • the invention relates to the field of satellite communications.
  • the invention relates more particularly to a method and a system for controlling the pointing of a transmission antenna of a terminal in connection with a ground station via a satellite in order to align a transmission beam towards a satellite or to take a decision on compliance with antenna off-axis radiation standards.
  • it can also be used for a direct visibility link (in English, Line of Sight, LOS).
  • Satellite communication systems involve ground stations in communication with satellites through which pass signals from satellite communication terminals.
  • a terminal transmits a radiofrequency signal via its antenna which points towards the satellite which is equipped with a transponder retransmitting the signal towards a ground station.
  • the alignment of the transmission and reception beams of the terminals is obtained by the mechanical design of these antennas for which their axes are collinear.
  • the only alignment of the reception beam towards the satellite makes it possible to guarantee the alignment of the transmission beam towards this same satellite.
  • these antennas like low profile antennas, have a radiation surface projected along the line of sight which is asymmetrical.
  • the radiation patterns have a plane of high directivity in which the main lobe is narrow and an orthogonal plane of low directivity in which the main lobe is wide.
  • the invention meets these needs.
  • the invention proposes according to a first aspect a method for controlling a transmission antenna of a terminal connected to a ground station, the antenna pointing either towards the ground station, or towards a satellite configured to relaying a signal from the antenna to the ground station along an effective line of sight, said method comprising the following steps implemented in an antenna control unit of the terminal:
  • the predetermined trigger date repeats according to a sequence known to both the terminal and the ground station;
  • the determination of a value representative of the fortuitous depointing comprises the steps of: comparing the level variation of the signal received with a template of curves dependent on the fortuitous depointing of the antenna of the terminal; selection of a representative value designating the curve of the template presenting the greatest resemblance to a level variation of the received signal.
  • the angular misalignment movement is confined to the main radiation lobe of the terminal antenna.
  • the ground station includes a step for controlling the transmission of the terminal by the ground station when it detects a variation in level or an angular misalignment greater than a determined threshold.
  • the ground station is configured to carry out sequences of realignment of its reception antenna by also using a method of measuring the signal level by the radio frequency unit which measures the received level when checking the antenna of the terminal
  • the ground station is only authorized to modify the pointing of its antenna between the predefined movement cycles of the terminal antenna.
  • the invention according to a second aspect relates to a system comprising at least one ground station and at least one terminal, said system being configured to implement a method according to the first aspect of the invention.
  • Control of the antenna of the transmitting terminal makes it possible to improve reception performance by the ground station. Indeed, the Applicant has observed that any variation in the depointing on transmission leads to a reduction in the power of the signal received by the ground station, which is detrimental to communication.
  • FIG. 1 illustrates an architecture for implementing the invention comprising a terminal, a ground station and a satellite;
  • FIG. 2 illustrates steps of a method of an antenna of a terminal pointing towards a satellite or a ground station according to an embodiment of the invention.
  • Figure 1 illustrates a satellite communication system in which a terminal 1 is in communication with a ground station 2 (in English, ground station or gateway) possibly via a satellite 3.
  • a ground station 2 in English, ground station or gateway
  • Satellite 3 is used to relay communication signals to other communication equipment. Satellite 3 is adjacent to other satellites 4 which may, for example, form a constellation with satellite 3, or be in a position close to satellite 3 within the Clarke belt, in the case of geostationary satellites.
  • the satellites 3, 4 are for example satellites having low altitude orbits (in English Low Earth Orbit, LEO), geostationary orbits (in English, Geostationary Earth Orbit, GEO) or medium altitude orbits (in English Medium Earth Orbit, MEO).
  • the terminal 1 comprises an antenna 11 pointed towards the satellite 3 along a current line of sight 14 which constitutes the real instantaneous pointing direction of the terminal 1, and supposed to be that towards the satellite 3.
  • a beam as used in the introduction refers to the part of the main lobe of the radiation pattern in which the radiation from the antenna is close to the maximum.
  • the maximum axis of radiation is by definition the current line of sight.
  • the antenna 11 of the terminal 1 points towards the antenna 31 of the satellite 3.
  • the antenna 11 has a radiation pattern which can be symmetrical or asymmetrical around the current line of sight 14.
  • the radiation axis maximum of the diagram is by definition the current line of sight 14.
  • the antenna 11 can be a parabolic or electronic scanning antenna: the parabolic antenna has a transmission diagram aligned with that of reception along the current line of sight 14 while the electronically scanned antenna has a current line of sight on transmission 14 which may be different from the current line of sight on reception (not shown).
  • the antenna 11 and in particular its line of sight is controlled by an antenna control unit 12 (in English, Antenna Control Unit, ACU).
  • an antenna control unit 12 in English, Antenna Control Unit, ACU.
  • expected line of sight 13 is understood to mean the exact pointing axis towards the satellite 3.
  • the difference between the current line of sight 14 and the expected line of sight 13 is the depointing error (or angle of total depointing). This misalignment value is limited by regulation, otherwise the terminal 1 must reduce its transmission power, or even completely cut off the transmission so as not to interfere with the adjacent satellites 4 which have neighboring positions.
  • all boresight and depointing axis angles are angles in three-dimensional space and are therefore values made up of two numbers, in particular azimuth and elevation when choosing a spherical coordinate system.
  • the ground station 2 also comprises an antenna 21 in communication with the satellite 3.
  • This antenna 21 is a parabolic antenna or an electronically scanned antenna, which has an axis of sight 25. It is subsequently considered that the alignment of the antenna of ground station 2 along line of sight 25 is correct and stable or at least that the associated misalignment is small and varies slowly enough to be considered constant during the steps which will be described later. The same applies to the movements of the satellite and its antenna(s) 31.
  • the ground station 2 can be substituted for the satellite 3 and the line of sight of the ground station 2 is then aligned, but in the opposite direction, with the line of sight expected 13.
  • LOS line-of-sight
  • the transmitting antenna 11 of the terminal 1 presents a fortuitous depointing denoted co, that is to say that when its ACU 12 provides it with a pointing instruction equal to the expected angle of sight 13, its diagram actually points around the effective boresight 15.
  • the fortuitous misalignment ⁇ is then the error between the actual boresight 15 and the expected boresight 13, which is basically of unknown value since the effect can be assimilated to chance as that resulting from the aging phenomena of the antenna technology.
  • the ACU 12 can apply a voluntary depointing denoted 0 which means that the current pointing instruction is in fact the sum of the expected line of sight 13 and the voluntary depointing 0. Consequently, the antenna 11 points in this case according to the current line of sight 14 which can be considered as equal to the effective line of sight 15 to which we add the voluntary depointing 0. Indeed, the accidental depointing error is a function which varies very little with the setpoint angles, but the voluntary depointing is of low value compared to the width of the main lobe of the antenna. It follows that the current line of sight 14 deviates from the expected line of sight 13 by a total misalignment, the value of which is considered equal to the sum of the fortuitous misalignment and the voluntary misalignment co + 0.
  • the sighting axes 13, 14 or 15 are defined by an elevation angle and an azimuth angle.
  • the azimuth indicates the direction in the horizontal plane and the elevation the height with respect to the same plane.
  • the azimuth angle varies from -180° to +180° and the elevation angle from -90° to -90°.
  • the terminal 1 can be embedded on a mobile.
  • the azimuth and elevation setpoints of the ACU 12 are calculated in a frame linked to the mobile carrier and a change of frame must be established to obtain the elevation and azimuth angles as defined above (not described here). This means that the ACU 12 can advantageously contain or be connected to an inertial unit to have the attitude angles of the mobile carrier.
  • the terminal 1 and the ground station 2 each include a local time base for dating the received signals.
  • This local time base can be obtained by means of an internal clock (very stable local oscillator) or be slaved to a universal time base.
  • a satellite positioning system called GNSS in English, Global Navigation Satellite System
  • GPS Global Navigation Satellite System
  • Glonass Galileo
  • Beidu is a widely used universal time base.
  • the terminal 1 or the ground station 2 have visibility of constellations of satellites of a GNSS system (not shown).
  • the architecture of FIG. 1 implements a method for controlling the antenna 11 of the terminal 1 pointing towards a satellite 3 or a ground station 2 along the line of sight effective 15.
  • the ground station 2 comprises a radiofrequency unit 22 performing all processing on the received or transmitted signal (amplifiers, transmission and reception modules, frequency converters, modems, etc.), a processing unit 23 and a storage unit 24 for storing intermediate values and parameters necessary during the process.
  • the control method comprises steps implemented on the terminal 1 side but also on the ground station 2 side. Consequently, the terminal 1 and the ground station 2 must be perfectly synchronized.
  • step E1 the synchronization of the terminal constitutes a fundamental preliminary step of the method which makes it possible to readjust the local time base of the terminal 1 on that to which the ground station 2 refers.
  • GNSS global satellite positioning system
  • the ground station 2 and the terminal 2 By equipping the ground station 2 and the terminal 2 with a GNSS receiver, their time base can be synchronized on this universal base and therefore be aligned with precisions much lower than the need for the method described here (typically of the order of the ten milliseconds).
  • the dating made on arrival by the station can be corrected for the propagation time of the signal from the terminal 1 to the ground station 2. This propagation time is determined by means of the position of the satellite 2 obtained thanks to its ephemeris and the very approximate position of the terminal (a few thousand km or so). In the case of a LOS, it is in principle not necessary to perform a propagation time correction for the needs of the process.
  • Terminal 1 can synchronize with it as soon as it receives the signaling on initialization, then only from time to time (typically every 20 to 30 minutes as part of the process). The most efficient systems measure the round trip delay and take the propagation time into account to synchronize terminal 1.
  • control we mean the control of the pointing of the antenna but also the ability to allow or not the emission of a signal if the regulations in terms of emission are not respected.
  • a voluntary depointing movement around the effective line of sight 15 is triggered (step E2).
  • a movement is predefined, and includes a duration D around the effective line of sight 15.
  • it is periodic, and even more preferably circular or even sinusoidal, ellipsoidal, etc.
  • This movement is regularly repeated, triggered according to an equally predefined sequence of dates, for example following a period T greater than or equal to the duration D and initiated on an original date to. Beyond the duration D, the movement then ends with a return to 0 and the pointing rejoins the effective line of sight 15 until the next trigger in the sequence.
  • the movement of duration D repeats a curve of amplitude and direction in the plane perpendicular to the effective line of sight, according to an axis reference convention.
  • terminal 1 can take a few liberties with a limited number of parameters defining the movement cycle.
  • the orientation of the direction of origin of voluntary depointing may not be known by the ground station 2, in particular when the radiation pattern is of circular revolution.
  • the amplitude of the movement can also be more or less weighted depending on whether you are looking for a fine or coarse pointing adjustment, or even zero if the terminal 1 considers that it is already perfectly pointed.
  • the movement must be of low amplitude, i.e. it is circumscribed within a fraction of the main radiation lobe of the antenna 11 of the terminal 1 around the effective line of sight. Indeed, a movement of too high an amplitude would imply a significant loss of transmitted level (towards satellite 3 or directly towards ground station 2) and therefore a significant degradation of the signal received by ground station 2.
  • the antenna 11 of the terminal 1 transmits a signal to the satellite 3 (step E3) and the ground station 2 then receives the signals during this movement via of the satellite (step E4).
  • the ground station 2 receives a signal whose power is reduced by the value of loss of gain caused by the total misalignment applied at instant t minus the propagation time of the link with the satellite 3 This propagation time may not be completely negligible in the case of geostationary satellite communications.
  • the signals received are measured in power by the radio frequency unit 22 of the ground station 2 (step E5) then dated by its processing unit 23 on their reception (step E6).
  • the purpose of this dating is to allow an overall processing of the level variation curve stored in the unit 24 after reception of a complete cycle of the movement. To be able to identify the voluntary depointing value associated with a date of reception by the ground station 2, since the movement is a predefined convention between the terminal 1 and the ground station 2, it is then sufficient simply to know its date of emission in the time base of terminal 1.
  • the ground station 2 knows the voluntary depointing movement applied by the ACU 12 of the terminal 1 as well as their trigger dates, identical dates in the two time bases, due to the synchronization step (step E1).
  • the ground station 2 also knows in a deterministic manner the level variation of the signals received as a function of the effective depointing angle of the antenna 11 of the terminal 1. This knowledge is obtained by a reference measurement of the radiation pattern of the main lobe of the antenna 11 to the qualification of the terminal model 1 and are stored in the storage unit 23 of the ground station 2.
  • a variation curve template is then deduced therefrom during the voluntary depointing movement cycle which is a function of the accidental depointing and the degrees of freedom available to the terminal 1 such as, for example, the overall amplitude of the depointing movement.
  • the level variation of the received signal is compared with the template.
  • this comparison makes it possible to select the representative value, dependent on the fortuitous misalignment, for which the variation in power of the signal received most closely resembles the template (step E7).
  • the variation in power of the received signal exhibits maxima when the voluntary misalignment is opposite to the direction of the accidental misalignment and minima when it is in the same direction.
  • the optimization criterion for determining the value representative of the fortuitous misalignment is, in a preferred embodiment, a minimization of the quadratic error between the template and the power level measurement over the entire movement cycle.
  • the movement is circular and regular around the effective line of sight, with an amplitude corresponding to x dB of gain reduction of the symmetrical main lobe of the antenna 11 (shift of 0 X CJB /2).
  • the template is then made up of sinusoids and the one most similar to the level variation curve has amplitude y dB and phase ⁇ p, i.e. the maximum at +y/2 dB is at instant D. ⁇ /2 ⁇ T and the minimum at -y/2 dB at instant D. ⁇ /2TT+D/2 from the beginning of the movement.
  • the couple y and ⁇ /2 ⁇ T constitutes a representative value all designated allowing the terminal 1 to determine the angular value of its fortuitous depointing, in its axis reference convention (in the broad sense, the value of an m-tuple is made up of m numbers).
  • the number x is also known to the ground station 2, the latter can itself determine the fortuitous misalignment value co and send directly to the terminal 1 the correction value - ⁇ to be applied in its axis coordinate system.
  • this value representative of the fortuitous depointing is transmitted to the terminal 1 via the radiofrequency unit 22 (step E8) which can deduce therefrom with good precision the angular value of the fortuitous depointing as well as the value of the effective depointing. Then, the terminal 1 adjusts the angle of its effective line of sight (step E9) by an opposite correction. The intentional depointing movement (around the effective line of sight 15) now takes place around him.
  • the method thus constitutes a servo loop tending to quickly cancel the fortuitous misalignment and therefore to make the effective line of sight 15 correspond to the expected line of sight 13.
  • the antenna 11 of the terminal 1 is then perfectly pointed since the fortuitous and voluntary depointings are harmed.
  • the ground station 2 can instruct the terminal 1 to cut off its transmission (step E10). To do this, the ground station 2 transmits to the terminal 1 an order in its satellite communication signaling protocol (not described here).
  • the measurement carried out by the ground station 2 during the method does not require any communication, it suffices that the terminal 1 is initially synchronized in the tens of minutes preceding the voluntary depointing movement. It can be carried out while the terminal is transmitting a very low level carrier without transmitting data, which may constitute a degraded mode of operation of the terminal adopted so as not to jeopardize either the communications of the system or those of the adjacent satellites, whereas the ACU 12 or the antenna 11 of the terminal are faulty. The system can also agree that, when the terminal 1 does not receive its regular signaling data (including a pointing correction among other instructions) it switches to this degraded mode or cuts its transmission.
  • the station is autonomous to take these decisions, the system is then made very reliable vis-à-vis the constraints of the regulations, even though the risk of failure of the terminal 1 is not negligible.
  • the ground station 2 must also implement, from time to time, a verification of the pointing of its antenna during a dedicated "step track" procedure which also leads it to slightly depoint its line of sight reception (step E11).
  • the procedure for pointing the antenna 21 of the ground station 2 requires a device for measuring the signal level received in the radiofrequency unit 22.
  • this same resource is used for the two procedures for measuring the effective depointing of the terminal in transmission and the station in reception. It must then be ensured that these procedures do not interfere but lead to correct depointing estimates.
  • the depointing cycles for the terminal 1 and the ground station 2 can be multiplexed in time to prevent them from taking place simultaneously. It is also possible to carry out the depointing movement of the terminal within a fixed depointing range of the "step track" procedure of the ground station 2. In general, it is sufficient for the station to ensure that modify the pointing of its antenna only outside the cycles of the antenna depointing movement 11. The time intervals beyond the duration D of the movement until the resumption of the following depointing cycle can be used in this goal.
  • the axis reference convention is preferably aligned with the directions of greater and lesser directivity of the radiation pattern.
  • the ground station 2 can translate the level variations into fortuitous misalignment since the antenna pattern is also defined in this frame. It then does not need to know the angle of bias (in English, skew) to determine the misalignment in each main direction of the antenna (of greater and lesser directivity).
  • the pointing correction instructions are then also sent back to this reference which is of course known to the ACU 12.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Astronomy & Astrophysics (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Radio Relay Systems (AREA)

Abstract

The invention relates to a method for controlling a transmit antenna (11) of a terminal (1) connected to a ground station (2), the antenna (11) pointing either towards the ground station (2) or towards a satellite (3) configured to relay a signal from the antenna to the ground station (2) along an actual line of sight (15), the method comprising the following steps, which are implemented in an antenna control unit (12) of the terminal (1): - synchronising a time base of the terminal (1) with a time base of a ground station (2), the ground station being configured to be in communication with the terminal (1).

Description

DESCRIPTION DESCRIPTION
TITRE DE L’INVENTION : Procédé et système de contrôle d’une antenne dans un système de communications par satellite TITLE OF THE INVENTION: Method and system for controlling an antenna in a satellite communications system
DOMAINE TECHNIQUE TECHNICAL AREA
L’invention concerne le domaine des communications par satellite. L’invention concerne plus particulièrement un procédé et un système de contrôle du pointage d’une antenne d’émission d’un terminal en liaison avec une station sol via un satellite afin d’aligner un faisceau d’émission vers un satellite ou de prendre une décision relative au respect des normes relatives au rayonnement hors axe de l’antenne. De façon alternative, elle peut aussi être employée pour une liaison en visibilité directe (en anglais, Line of Sight, LOS). The invention relates to the field of satellite communications. The invention relates more particularly to a method and a system for controlling the pointing of a transmission antenna of a terminal in connection with a ground station via a satellite in order to align a transmission beam towards a satellite or to take a decision on compliance with antenna off-axis radiation standards. Alternatively, it can also be used for a direct visibility link (in English, Line of Sight, LOS).
ETAT DE LA TECHNIQUE STATE OF THE ART
Les systèmes de communication par satellite impliquent des stations au sol en communication avec des satellites par lesquelles transitent des signaux issus de terminaux de communication par satellites. Satellite communication systems involve ground stations in communication with satellites through which pass signals from satellite communication terminals.
En particulier, au cours d’une communication, en émission, un terminal émet un signal radiofréquence par son antenne qui pointe vers le satellite lequel est muni d’un transpondeur réémettant le signal vers une station au sol. In particular, during a communication, in transmission, a terminal transmits a radiofrequency signal via its antenna which points towards the satellite which is equipped with a transponder retransmitting the signal towards a ground station.
La réglementation internationale des télécommunications, impose que le faisceau d’antenne à l’émission des terminaux de communication par satellite soit rigoureusement aligné afin de ne pas perturber les communications sur les satellites adjacents. International telecommunications regulations require that the antenna beam at the transmission of satellite communication terminals be strictly aligned so as not to disturb communications on adjacent satellites.
Pour les antennes à réflecteurs, l’alignement des faisceaux émission et réception des terminaux est obtenu par la conception mécanique de ces antennes pour lesquelles leurs axes sont colinéaires. Le seul alignement du faisceau réception vers le satellite permet de garantir l’alignement du faisceau émission vers ce même satellite. For antennas with reflectors, the alignment of the transmission and reception beams of the terminals is obtained by the mechanical design of these antennas for which their axes are collinear. The only alignment of the reception beam towards the satellite makes it possible to guarantee the alignment of the transmission beam towards this same satellite.
Pour les antennes à balayage électronique, qui permettent des pointages indépendants des faisceaux d’émission et de réception, le pointage à l’émission s’effectue par recopie de l’angle de réception en consigne d’angle à l’émission, mais ce processus de commande en boucle ouverte, parfaitement étalonné à la mise au point en laboratoire, peut subir des dérives liées au vieillissement des composants électroniques ou mécaniques, conséquemment aux cycles thermiques subis par les équipements. For electronic scanning antennas, which allow independent pointing of the transmission and reception beams, the pointing on transmission is carried out by copying the reception angle into the transmission angle setpoint, but this open-loop control process, perfectly calibrated to laboratory development, can suffer drifts related to the aging of electronic or mechanical components, as a result of the thermal cycles undergone by the equipment.
De plus, ces antennes, à l’instar des antennes à bas profil, présentent une surface de rayonnement projetée selon l’axe de visée qui est asymétrique. Ainsi, les diagrammes de rayonnement présentent un plan de forte directivité selon lequel le lobe principal est étroit et un plan orthogonal de faible directivité selon lequel le lobe principal est large. In addition, these antennas, like low profile antennas, have a radiation surface projected along the line of sight which is asymmetrical. Thus, the radiation patterns have a plane of high directivity in which the main lobe is narrow and an orthogonal plane of low directivity in which the main lobe is wide.
L’application de la réglementation autorise un rayonnement hors axe vers les satellites adjacents d’un certain niveau maximal, ce qui se traduit par une tolérance d’erreur de pointage différente selon que fait la ceinture de Clarke (l’arc géostationnaire) avec l’axe de forte (ou de faible) directivité, c’est-à-dire l’angle de biais (en anglais : skew angle). The application of the regulations allows off-axis radiation to adjacent satellites of a certain maximum level, which results in a different pointing error tolerance depending on how much the Clarke belt (the geostationary arc) does with the axis of strong (or weak) directivity, that is to say the angle of bias (in English: skew angle).
Il est donc nécessaire de connaitre avec précision le dépointage de l’antenne dans chacun de ses plans pour vérifier s’il est cohérent avec la réglementation mais aussi de s’assurer que l’antenne point dans la bonne direction. It is therefore necessary to know precisely the offset of the antenna in each of its planes to check if it is consistent with the regulations but also to ensure that the antenna is pointing in the right direction.
EXPOSE DE L’INVENTION DISCLOSURE OF THE INVENTION
L’invention répond à ces besoins. The invention meets these needs.
A cet effet, l’invention propose selon un premier aspect un procédé de contrôle d’une antenne d’émission d’un terminal en connecté avec une station sol, l’antenne pointant soit vers la station sol, soit vers un satellite configuré pour relayer un signal issu de l’antenne vers la station sol selon un axe de visée effectif, ledit procédé comprenant les étapes suivantes mises en oeuvre dans une unité de contrôle d’antenne du terminal : To this end, the invention proposes according to a first aspect a method for controlling a transmission antenna of a terminal connected to a ground station, the antenna pointing either towards the ground station, or towards a satellite configured to relaying a signal from the antenna to the ground station along an effective line of sight, said method comprising the following steps implemented in an antenna control unit of the terminal:
- synchronisation d’une base de temps du terminal avec une base de temps d’une station sol, ladite station sol étant configurée pour être en communication avec le terminal ; - synchronization of a time base of the terminal with a time base of a ground station, said ground station being configured to be in communication with the terminal;
- déclenchement à une date prédéterminée dans la base de temps du terminal synchronisée d’un cycle de mouvement de dépointage volontaire de l’antenne d’émission de manière à faire varier l’axe de visée effectif selon un axe de visée courant variable au cours dudit cycle ; - triggering on a predetermined date in the time base of the synchronized terminal of a voluntary depointing movement cycle of the transmitting antenna so as to vary the effective line of sight according to a variable current line of sight during said cycle;
- émission par l’antenne du terminal d’un signal vers la station sol au cours dudit cycle de dépointage selon ledit axe de visée courant variant selon ledit cycle ; - transmission by the antenna of the terminal of a signal to the ground station during said depointing cycle according to said current line of sight varying according to said cycle;
- réception à la fin dudit cycle, d’un signal émis par la station sol, ledit signal comprenant une valeur représentative à partir de laquelle le terminal peut en déduire l’angle de dépointage fortuit défini entre l’axe de visée effectif et l’axe de visée attendu ; - correction, de l’axe de visée effectif de l’angle de dépointage fortuit, de manière à ce que l’axe de visée effectif soit aligné avec l’axe de visé attendu. - reception at the end of said cycle, of a signal emitted by the ground station, said signal comprising a representative value from which the terminal can deduce the angle of fortuitous depointing defined between the effective line of sight and the line of sight expected; - correction, of the effective line of sight of the accidental misalignment angle, so that the effective line of sight is aligned with the expected line of sight.
L’invention est avantageusement complétée par les caractéristiques suivantes, prises seules ou en une quelconque de leur combinaison techniquement possible : The invention is advantageously completed by the following characteristics, taken alone or in any of their technically possible combination:
- La date de déclenchement prédéterminée se répète selon une séquence connue à la fois du terminal et de la station sol ; - The predetermined trigger date repeats according to a sequence known to both the terminal and the ground station;
- le cycle de mouvement connu du terminal et de la station sol ; - the known movement cycle of the terminal and the ground station;
- il comprend en outre les étapes suivantes mises en oeuvre par la station sol (2) : réception (E4) de signaux émis par le terminal au cours du mouvement de dépointage volontaire autour d’un axe de visée effectif de l’antenne vers le satellite ou la station sol ; mesure du niveau de réception du signal; datation de la courbe de niveau de réception de signal selon la base de temps de la station sol ; détermination à partir de la courbe de niveau, d’une valeur représentative du dépointage fortuit de l’antenne d’émission du terminal ; transmission de cette valeur représentative ainsi déterminée au terminal de manière à ce qu’il détermine son angle de dépointage fortuit et corrige l’axe de visée effectif de l’antenne ; - it further comprises the following steps implemented by the ground station (2): reception (E4) of signals emitted by the terminal during the voluntary depointing movement around an effective line of sight of the antenna towards the satellite or ground station; signal reception level measurement; dating of the signal reception level curve according to the time base of the ground station; determination from the level curve, of a value representative of the fortuitous misalignment of the terminal's transmission antenna; transmission of this representative value thus determined to the terminal so that it determines its accidental misalignment angle and corrects the effective line of sight of the antenna;
- la détermination d’une valeur représentative du dépointage fortuit comprend les étapes de : comparaison de la variation de niveau du signal reçu avec un gabarit de courbes dépendantes du dépointage fortuit de l’antenne du terminal ; sélection d’une valeur représentative désignant la courbe du gabarit présentant la plus grande ressemblance avec une variation de niveau du signal reçu. - the determination of a value representative of the fortuitous depointing comprises the steps of: comparing the level variation of the signal received with a template of curves dependent on the fortuitous depointing of the antenna of the terminal; selection of a representative value designating the curve of the template presenting the greatest resemblance to a level variation of the received signal.
- le mouvement de dépointage angulaire est circonscrit dans le lobe principal de rayonnement de l’antenne du terminal. - the angular misalignment movement is confined to the main radiation lobe of the terminal antenna.
- il comprend une étape de commande de coupure de l’émission du terminal par la station sol lorsqu’elle détecte une variation de niveau ou un dépointage angulaire supérieurs à un seuil déterminé. - it includes a step for controlling the transmission of the terminal by the ground station when it detects a variation in level or an angular misalignment greater than a determined threshold.
- la station sol est configurée pour procéder à des séquences de réalignement de son antenne de réception en utilisant aussi une méthode de mesure du niveau de signal par l’unité radiofréquence qui effectue la mesure de niveau reçu lors du contrôle de l’antenne du terminal - the ground station is configured to carry out sequences of realignment of its reception antenna by also using a method of measuring the signal level by the radio frequency unit which measures the received level when checking the antenna of the terminal
- la station sol ne s’autorise à modifier le pointage de son antenne qu’entre les cycles de mouvement prédéfinis de l’antenne du terminal. - the ground station is only authorized to modify the pointing of its antenna between the predefined movement cycles of the terminal antenna.
- la base de temps du terminal est corrigée du temps de propagation du signal du terminal à la station. L’invention selon un second aspect concerne un système comprenant au moins une station sol et au moins un terminal, ledit système étant configuré pour mettre en oeuvre un procédé selon le premier aspect de l’invention. - the time base of the terminal is corrected by the propagation time of the signal from the terminal to the station. The invention according to a second aspect relates to a system comprising at least one ground station and at least one terminal, said system being configured to implement a method according to the first aspect of the invention.
Les avantages de l’invention sont multiples. The advantages of the invention are multiple.
Le contrôle de l’antenne du terminal émetteur permet d’améliorer les performances de réception par la station sol. En effet, la Demanderesse a observé que toute variation du dépointage à l’émission conduisait à une réduction de la puissance du signal reçu par la station sol, néfaste pour la communication. Control of the antenna of the transmitting terminal makes it possible to improve reception performance by the ground station. Indeed, the Applicant has observed that any variation in the depointing on transmission leads to a reduction in the power of the signal received by the ground station, which is detrimental to communication.
PRESENTATION DES FIGURES PRESENTATION OF FIGURES
D’autres caractéristiques, buts et avantages de l’invention ressortiront de la description qui suit, qui est purement illustrative et non limitative, et qui doit être lue en regard des dessins annexés sur lesquels : Other characteristics, objects and advantages of the invention will emerge from the description which follows, which is purely illustrative and not limiting, and which must be read in conjunction with the appended drawings in which:
La figure 1 illustre une architecture pour la mise en oeuvre de l’invention comprenant un terminal, une station sol et un satellite ; FIG. 1 illustrates an architecture for implementing the invention comprising a terminal, a ground station and a satellite;
La figure 2 illustre des étapes d’un procédé d’une antenne d’un terminal pointant vers un satellite ou une station sol selon un mode de réalisation de l’invention. FIG. 2 illustrates steps of a method of an antenna of a terminal pointing towards a satellite or a ground station according to an embodiment of the invention.
Sur l’ensemble des figures les éléments similaires portent des références identiques. In all the figures, similar elements bear identical references.
DESCRIPTION DETAILLEE DETAILED DESCRIPTION
La figure 1 illustre un système de communication par satellites dans lequel un terminal 1 est en communication avec une station sol 2 (en anglais, ground station ou gateway) éventuellement par l’intermédiaire d’un satellite 3. Figure 1 illustrates a satellite communication system in which a terminal 1 is in communication with a ground station 2 (in English, ground station or gateway) possibly via a satellite 3.
Le satellite 3 permet de relayer les signaux de communications vers d’autres équipements de communication. Le satellite 3 est adjacent à d’autres satellites 4 qui peuvent, par exemple, former une constellation avec le satellite 3, ou être sur une position proche du satellite 3 au sein de la ceinture de Clarke, dans le cas de satellites géostationnaires. Satellite 3 is used to relay communication signals to other communication equipment. Satellite 3 is adjacent to other satellites 4 which may, for example, form a constellation with satellite 3, or be in a position close to satellite 3 within the Clarke belt, in the case of geostationary satellites.
Les satellites 3, 4 sont par exemple des satellites ayant des orbites basses altitudes (en anglais Low Earth Orbit, LEO), des orbites géostationnaires (en anglais, Geostationnary Earth Orbit, GEO) ou des orbites moyennes altitudes (en anglais Medium Earth Orbit, MEO). The satellites 3, 4 are for example satellites having low altitude orbits (in English Low Earth Orbit, LEO), geostationary orbits (in English, Geostationary Earth Orbit, GEO) or medium altitude orbits (in English Medium Earth Orbit, MEO).
Le terminal 1 comporte une antenne 11 pointée vers le satellite 3 selon un axe de visée courant 14 qui constitue la direction réelle instantanée de pointage du terminal 1 , et sensé être celle vers le satellite 3. The terminal 1 comprises an antenna 11 pointed towards the satellite 3 along a current line of sight 14 which constitutes the real instantaneous pointing direction of the terminal 1, and supposed to be that towards the satellite 3.
Un faisceau tel qu’utilisé dans l’introduction désigne la partie du lobe principal du diagramme de rayonnement dans laquelle le rayonnement de l’antenne est proche du maximum. Comme on veut maximiser l’énergie reçue par le satellite ou la station sol, l’axe maximal de rayonnement est par définition l’axe de visée courant. Quand l’antenne est à balayage électronique, celui-ci peut être piloté indépendamment du positionnement mécanique de l’antenne. A beam as used in the introduction refers to the part of the main lobe of the radiation pattern in which the radiation from the antenna is close to the maximum. As we want to maximize the energy received by the satellite or the ground station, the maximum axis of radiation is by definition the current line of sight. When the antenna is electronically scanned, it can be controlled independently of the mechanical positioning of the antenna.
En particulier, l’antenne 11 du terminal 1 pointe vers l’antenne 31 du satellite 3. L’antenne 11 présente un diagramme de rayonnement qui peut être symétrique ou asymétrique autour de l’axe de visée courant 14. L’axe de rayonnement maximal du diagramme est par définition l’axe de visée courant 14. L’antenne 11 peut être une antenne parabolique ou à balayage électronique : l’antenne parabolique présente un diagramme d’émission aligné sur celui de réception selon l’axe de visée courant 14 tandis que l’antenne à balayage électronique présente un axe de visée courant à l’émission 14 qui peut être différent de l’axe de visée courant à la réception (non représenté). In particular, the antenna 11 of the terminal 1 points towards the antenna 31 of the satellite 3. The antenna 11 has a radiation pattern which can be symmetrical or asymmetrical around the current line of sight 14. The radiation axis maximum of the diagram is by definition the current line of sight 14. The antenna 11 can be a parabolic or electronic scanning antenna: the parabolic antenna has a transmission diagram aligned with that of reception along the current line of sight 14 while the electronically scanned antenna has a current line of sight on transmission 14 which may be different from the current line of sight on reception (not shown).
L’antenne 11 et notamment son axe de visée est contrôlé par une unité de contrôle de l’antenne 12 (en anglais, Antenna Control Unit, ACU). The antenna 11 and in particular its line of sight is controlled by an antenna control unit 12 (in English, Antenna Control Unit, ACU).
On entend par « axe de visé attendu 13 », l’axe exact de pointage vers le satellite 3. La différence entre l’axe de visée courant 14 et l’axe de visée attendu 13 est l’erreur de dépointage (ou angle de dépointage total). Cette valeur de dépointage est réglementairement limitée faute de quoi le terminal 1 doit réduire sa puissance d’émission, voire couper totalement l’émission pour ne faut pas brouiller les satellites adjacents 4 qui ont des positions voisines. Dans ce qui précède, tous les angles d’axes de visée et de dépointage sont des angles dans l’espace à trois dimensions et sont donc des valeurs constituées de deux nombres, en particulier l’azimut et l’élévation lorsqu’on choisit un système de coordonnées sphériques. The term “expected line of sight 13” is understood to mean the exact pointing axis towards the satellite 3. The difference between the current line of sight 14 and the expected line of sight 13 is the depointing error (or angle of total depointing). This misalignment value is limited by regulation, otherwise the terminal 1 must reduce its transmission power, or even completely cut off the transmission so as not to interfere with the adjacent satellites 4 which have neighboring positions. In the above, all boresight and depointing axis angles are angles in three-dimensional space and are therefore values made up of two numbers, in particular azimuth and elevation when choosing a spherical coordinate system.
La station sol 2 comporte également une antenne 21 en communication avec le satellite 3. Cette antenne 21 est une antenne parabolique ou une antenne à balayage électronique, qui présente un axe de visée 25. On considère par la suite que l’alignement de l’antenne de la station sol 2 selon l’axe de visée 25 est correct et stable ou tout au moins que le dépointage associé est faible et varie suffisamment lentement pour être considéré comme constant lors des étapes qui seront décrites par la suite. Il en va de même pour les mouvements du satellite et de son/ses antenne(s) 31. The ground station 2 also comprises an antenna 21 in communication with the satellite 3. This antenna 21 is a parabolic antenna or an electronically scanned antenna, which has an axis of sight 25. It is subsequently considered that the alignment of the antenna of ground station 2 along line of sight 25 is correct and stable or at least that the associated misalignment is small and varies slowly enough to be considered constant during the steps which will be described later. The same applies to the movements of the satellite and its antenna(s) 31.
De manière alternative, dans le cas où la liaison est en visée directe (LOS), on peut substituer la station sol 2 au satellite 3 et l’axe de visée de la station sol 2 est alors alignée mais en sens opposé, avec l’axe de visée attendu 13. Alternatively, in the case where the link is in line-of-sight (LOS), the ground station 2 can be substituted for the satellite 3 and the line of sight of the ground station 2 is then aligned, but in the opposite direction, with the line of sight expected 13.
Dans la pratique, l’antenne d’émission 11 du terminal 1 présente un dépointage fortuit noté co, c’est-à-dire que lorsque son ACU 12 lui fournit une consigne de pointage égale à l’angle de visée attendu 13, son diagramme pointe en fait autour de l’axe de visée effectif 15. Le dépointage fortuit œ est alors l’erreur entre l’axe de visée effectif 15 et l’axe de visée attendu 13, qui est fondamentalement de valeur inconnue puisque l’effet peut être assimilé au hasard comme celui issu des phénomènes de vieillissement de la technologie de l’antenne. In practice, the transmitting antenna 11 of the terminal 1 presents a fortuitous depointing denoted co, that is to say that when its ACU 12 provides it with a pointing instruction equal to the expected angle of sight 13, its diagram actually points around the effective boresight 15. The fortuitous misalignment œ is then the error between the actual boresight 15 and the expected boresight 13, which is basically of unknown value since the effect can be assimilated to chance as that resulting from the aging phenomena of the antenna technology.
De surcroit, comme on le verra par la suite, l’ACU 12 peut appliquer un dépointage volontaire noté 0 ce qui fait que la consigne courante de pointage est en fait la somme de l’axe de visée attendu 13 et du dépointage volontaire 0. En conséquence, l’antenne 11 pointe dans ce cas selon l’axe de visée courant 14 qui peut être considéré comme égal à l’axe de visée effectif 15 auquel on ajoute le dépointage volontaire 0. En effet, l’erreur de dépointage fortuit est une fonction qui varie très peu avec les angles de consigne or le dépointage volontaire est de valeur faible devant la largeur du lobe principal de l’antenne. Il s’ensuit que l’axe de visée courant 14 s’écarte de l’axe de visée attendu 13 par un dépointage total dont la valeur est considérée comme égale à la somme du dépointage fortuit et du dépointage volontaire co + 0. In addition, as will be seen later, the ACU 12 can apply a voluntary depointing denoted 0 which means that the current pointing instruction is in fact the sum of the expected line of sight 13 and the voluntary depointing 0. Consequently, the antenna 11 points in this case according to the current line of sight 14 which can be considered as equal to the effective line of sight 15 to which we add the voluntary depointing 0. Indeed, the accidental depointing error is a function which varies very little with the setpoint angles, but the voluntary depointing is of low value compared to the width of the main lobe of the antenna. It follows that the current line of sight 14 deviates from the expected line of sight 13 by a total misalignment, the value of which is considered equal to the sum of the fortuitous misalignment and the voluntary misalignment co + 0.
On précise que les axes de visée 13, 14 ou 15 sont définis par un angle d’élévation et un angle azimutal. L’azimut indique la direction dans le plan horizontal et l’élévation la hauteur par rapport au même plan. L’angle d’azimut varie de -180° à +180° et celui d’élévation de -90°à-90°. Toutefois, le terminal 1 peut être embarqué sur un mobile. Dans ce cas, les consignes d’azimut et élévations de l’ACU 12 sont calculées dans un repère lié au mobile porteur et il faut établir un changement de repère pour obtenir les angles d’élévation et azimut tels que définis ci-dessus (non décrit ici). Ceci signifie que l’ACU 12 peut avantageusement contenir ou être relié à une centrale inertielle pour disposer des angles d’attitude du mobile porteur. Dans ce qui suit, on ignore ce dispositif et on suppose que l’ACU 12 est capable de calculer azimut et élévation de façon autonome dans un repère terrestre. Le terminal 1 et la station sol 2 comprennent chacun une base de temps locale pour dater les signaux reçus. Cette base de temps locale peut être obtenue au moyen d’une horloge interne (oscillateur local très stable) ou être asservie sur une base de temps universelle. Un système de positionnement par satellites dit GNSS (en anglais, Global Navigation Satellite System) comme par exemple GPS, Glonass, Galiléo ou Beidu est une base de temps universelle très utilisée. Dans ce dernier cas, le terminal 1 ou la station au sol 2 ont en visibilité des constellations de satellites d’un système GNSS (non représentées). It is specified that the sighting axes 13, 14 or 15 are defined by an elevation angle and an azimuth angle. The azimuth indicates the direction in the horizontal plane and the elevation the height with respect to the same plane. The azimuth angle varies from -180° to +180° and the elevation angle from -90° to -90°. However, the terminal 1 can be embedded on a mobile. In this case, the azimuth and elevation setpoints of the ACU 12 are calculated in a frame linked to the mobile carrier and a change of frame must be established to obtain the elevation and azimuth angles as defined above (not described here). This means that the ACU 12 can advantageously contain or be connected to an inertial unit to have the attitude angles of the mobile carrier. In what follows, this device is ignored and it is assumed that the ACU 12 is capable of calculating azimuth and elevation autonomously in a terrestrial reference. The terminal 1 and the ground station 2 each include a local time base for dating the received signals. This local time base can be obtained by means of an internal clock (very stable local oscillator) or be slaved to a universal time base. A satellite positioning system called GNSS (in English, Global Navigation Satellite System) such as GPS, Glonass, Galileo or Beidu is a widely used universal time base. In the latter case, the terminal 1 or the ground station 2 have visibility of constellations of satellites of a GNSS system (not shown).
L’homme du métier connaît bien des techniques pour asservir le pointage de l’antenne de réception d’un terminal. Ces techniques sont connues sous leur dénomination anglaise « conical scan » ou « step track ». Dans les deux cas, il s’agit d’annuler le dépointage fortuit en appliquant des dépointages volontaires répartis autour de l’axe de visée effectif. Dans le premier cas, le mouvement est continu, et forme typiquement un cercle centré sur l’axe de visée effectif, dans le second un certain nombre de positions de dépointage volontaire symétriquement réparties autour de l’axe de visée effectif sont appliqués. La mesure de la puissance reçue du signal utile fournit une courbe ou des paliers de niveaux dont on est capable de déduire le dépointage fortuit. Le terminal corrige la consigne de pointage en retranchant le dépointage fortuit trouvé. Those skilled in the art know many techniques for controlling the pointing of the reception antenna of a terminal. These techniques are known by their English name “conical scan” or “step track”. In both cases, it is a question of canceling the fortuitous misalignment by applying voluntary misalignments distributed around the effective line of sight. In the first case, the movement is continuous, and typically forms a circle centered on the effective line of sight, in the second a certain number of voluntary depointing positions symmetrically distributed around the effective line of sight are applied. The measurement of the power received from the useful signal provides a curve or level stages from which one is able to deduce the fortuitous misalignment. The terminal corrects the pointing setpoint by subtracting the fortuitous misalignment found.
Pour pointer une antenne d’émission dont l’axe de visée n’est pas forcément colinéaire à celui de réception, une telle solution n’est pas simplement transposable de l’antenne de réception à celle d’émission pour deux raisons : la mesure de niveau doit être faite du côté de la station sol 2 et celle-ci ne connaît pas le dépointage volontaire appliqué par l’ACU 12 du terminal 1 à un instant donné. Une communication immédiate de ces valeurs à l’autre extrémité de la liaison, parait une solution simple. Cependant, outre le fait que ces communications régulières occasionnent un délai et occupent de la bande passante, le mécanisme serait alors peu robuste à des erreurs de communication, présentant un risque de dépointage supérieur aux valeurs autorisées par la réglementation. Il est fondamental que l’émission du terminal soit coupée de façon sûre lorsque sa puissance émise hors axe dépasse la valeur réglementairement autorisée et que ceci soit réalisé immédiatement et sans faute lorsque l’ACU 12 ou l’antenne 11 sont défaillants. To point a transmission antenna whose line of sight is not necessarily collinear with that of reception, such a solution cannot simply be transposed from the reception antenna to that of transmission for two reasons: the measurement level must be made on the side of the ground station 2 and the latter does not know the voluntary depointing applied by the ACU 12 of the terminal 1 at a given instant. Immediate communication of these values to the other end of the link seems a simple solution. However, in addition to the fact that these regular communications cause a delay and occupy bandwidth, the mechanism would then be not very robust to communication errors, presenting a risk of depointing greater than the values authorized by the regulations. It is essential that the transmission of the terminal be cut off in a safe manner when its off-axis transmitted power exceeds the regulatory authorized value and that this be done immediately and without fault when the ACU 12 or the antenna 11 are faulty.
Ainsi, en relation avec la figure 2, on met en oeuvre dans l’architecture de la figure 1 , un procédé de contrôle de l’antenne 11 du terminal 1 pointant vers un satellite 3 ou une station sol 2 selon l’axe de visée effectif 15. A ce titre, la station sol 2 comprend une unité radiofréquence 22 effectuant tous les traitements sur le signal reçu ou émis (amplificateurs, modules d’émission et réception, convertisseurs de fréquence, modems, etc.), une unité de traitement 23 et une unité de stockage 24 pour stocker des valeurs intermédiaires et des paramètres nécessaires au cours du procédé. Thus, in relation to FIG. 2, the architecture of FIG. 1 implements a method for controlling the antenna 11 of the terminal 1 pointing towards a satellite 3 or a ground station 2 along the line of sight effective 15. As such, the ground station 2 comprises a radiofrequency unit 22 performing all processing on the received or transmitted signal (amplifiers, transmission and reception modules, frequency converters, modems, etc.), a processing unit 23 and a storage unit 24 for storing intermediate values and parameters necessary during the process.
Le procédé de contrôle comprend des étapes mises en oeuvre côté terminal 1 mais aussi côté station sol 2. Dès, lors le terminal 1 et la station sol 2 doivent être parfaitement synchronisées. The control method comprises steps implemented on the terminal 1 side but also on the ground station 2 side. Consequently, the terminal 1 and the ground station 2 must be perfectly synchronized.
Par conséquent, la synchronisation du terminal constitue une étape préliminaire fondamentale du procédé qui permet de recaler la base de temps locale du terminal 1 sur celle à laquelle se réfère la station sol 2(étape E1 ). Consequently, the synchronization of the terminal constitutes a fundamental preliminary step of the method which makes it possible to readjust the local time base of the terminal 1 on that to which the ground station 2 refers (step E1).
A ce titre, plusieurs techniques de synchronisation sont possibles. La plus connue consiste à utiliser un système global de positionnement par satellite GNSS. En équipant la station sol 2 et le terminal 2 d’un récepteur GNSS, leur base de temps peut être synchronisée sur cette base universelle et donc être alignée avec des précisions très inférieures au besoin du procédé ici décrit (typiquement de l’ordre de la dizaine de millisecondes). De manière complémentaire, la datation faite à l’arrivée par la station peut être corrigée du temps de propagation du signal du terminal 1 à la station sol 2. Ce temps de propagation est déterminé au moyen de la position du satellite 2 obtenue grâce à ses éphémérides et de la position très approximative du terminal (quelques milliers de km près). Dans le cas d’une LOS, il n’est en principe pas nécessaire d’effectuer une correction de temps de propagation pour le besoin du procédé. As such, several synchronization techniques are possible. The best known is to use a global satellite positioning system GNSS. By equipping the ground station 2 and the terminal 2 with a GNSS receiver, their time base can be synchronized on this universal base and therefore be aligned with precisions much lower than the need for the method described here (typically of the order of the ten milliseconds). In addition, the dating made on arrival by the station can be corrected for the propagation time of the signal from the terminal 1 to the ground station 2. This propagation time is determined by means of the position of the satellite 2 obtained thanks to its ephemeris and the very approximate position of the terminal (a few thousand km or so). In the case of a LOS, it is in principle not necessary to perform a propagation time correction for the needs of the process.
Alternativement, de nombreux systèmes de télécommunications par satellite diffusent dans leur signalisation une date du système, c’est-à-dire la base de temps de la station sol 2 elle-même synchronisée sur une base de temps universelle. Le terminal 1 peut se synchroniser dessus dès lors qu’il reçoit la signalisation à son initialisation, puis uniquement de temps à autre (typiquement toutes les 20 à 30 minutes dans le cadre du procédé). Les systèmes les plus performants mesurent le temps de propagation aller-retour (en anglais, round trip delay) et tiennent compte du temps de propagation pour synchroniser le terminal 1. Alternatively, many satellite telecommunications systems broadcast in their signaling a system date, i.e. the time base of ground station 2 itself synchronized on a universal time base. Terminal 1 can synchronize with it as soon as it receives the signaling on initialization, then only from time to time (typically every 20 to 30 minutes as part of the process). The most efficient systems measure the round trip delay and take the propagation time into account to synchronize terminal 1.
Dans ce qui suit, on entend par contrôle, le contrôle du pointage de l’antenne mais aussi la capacité de permettre ou non une émission d’un signal si les réglementations en termes d’émission ne sont pas respectées. In what follows, by control we mean the control of the pointing of the antenna but also the ability to allow or not the emission of a signal if the regulations in terms of emission are not respected.
Pour estimer le dépointage angulaire fortuit de l’antenne 11 d’émission du terminal 1 , un mouvement de dépointage volontaire autour de l’axe de visée effectif 15 est déclenché (étape E2). Un tel mouvement est prédéfini, et comprend une durée D autour de l’axe de visée effectif 15. Dans un mode de réalisation préféré, il est périodique, et encore plus préférentiellement circulaire voire sinusoïdal, ellipsoïdal, etc. Ce mouvement est régulièrement répété, déclenché selon une séquence de dates également prédéfinie, par exemple suivant une période T supérieure ou égale à la durée D et initié à une date d’origine to. Au-delà de la durée D, le mouvement se termine alors par un retour à 0 et le pointage rejoint l’axe de visée effectif 15 jusqu’au déclenchement suivant dans la séquence. Le mouvement de durée D répète une courbe d’amplitude et de direction dans le plan perpendiculaire à l’axe de visée effectif, selon une convention de repère d’axes. To estimate the fortuitous angular depointing of the transmitting antenna 11 of the terminal 1, a voluntary depointing movement around the effective line of sight 15 is triggered (step E2). Such a movement is predefined, and includes a duration D around the effective line of sight 15. In a preferred embodiment, it is periodic, and even more preferably circular or even sinusoidal, ellipsoidal, etc. This movement is regularly repeated, triggered according to an equally predefined sequence of dates, for example following a period T greater than or equal to the duration D and initiated on an original date to. Beyond the duration D, the movement then ends with a return to 0 and the pointing rejoins the effective line of sight 15 until the next trigger in the sequence. The movement of duration D repeats a curve of amplitude and direction in the plane perpendicular to the effective line of sight, according to an axis reference convention.
La séquence des dates de déclenchement ainsi que cycle de mouvement sont avantageusement connus du terminal 1 et de la station sol 2. Dans certaines variantes, le terminal 1 peut prendre quelques libertés sur un nombre limité de paramètres définissant le cycle de mouvement. Par exemple, l’orientation de la direction d’origine de dépointage volontaire peut ne pas être connue par la station sol 2, notamment lorsque le diagramme de rayonnement est de révolution circulaire. L’amplitude du mouvement peut aussi être plus ou moins pondérée selon que l’on cherche un ajustement de pointage fin ou grossier, ou voire nul si le terminal 1 estime être déjà parfaitement pointé. The sequence of trigger dates as well as movement cycle are advantageously known to terminal 1 and to ground station 2. In certain variants, terminal 1 can take a few liberties with a limited number of parameters defining the movement cycle. For example, the orientation of the direction of origin of voluntary depointing may not be known by the ground station 2, in particular when the radiation pattern is of circular revolution. The amplitude of the movement can also be more or less weighted depending on whether you are looking for a fine or coarse pointing adjustment, or even zero if the terminal 1 considers that it is already perfectly pointed.
En outre, le mouvement doit être d’amplitude faible c’est-à-dire qu’il est circonscrit dans une fraction du lobe principal de rayonnement de l’antenne 11 du terminal 1 autour de l’axe de visée effectif. En effet, un mouvement d’amplitude trop forte impliquerait une perte importante de niveau émis (vers le satellite 3 ou directement vers la station sol 2) et donc une dégradation importante du signal reçu par la station sol 2. In addition, the movement must be of low amplitude, i.e. it is circumscribed within a fraction of the main radiation lobe of the antenna 11 of the terminal 1 around the effective line of sight. Indeed, a movement of too high an amplitude would imply a significant loss of transmitted level (towards satellite 3 or directly towards ground station 2) and therefore a significant degradation of the signal received by ground station 2.
Pendant ce mouvement de dépointage volontaire autour de l’axe de visée effectif 15, l’antenne 11 du terminal 1 émet un signal vers le satellite 3 (étape E3) et la station sol 2 reçoit alors les signaux pendant ce mouvement par l’intermédiaire du satellite (étape E4). During this voluntary depointing movement around the effective line of sight 15, the antenna 11 of the terminal 1 transmits a signal to the satellite 3 (step E3) and the ground station 2 then receives the signals during this movement via of the satellite (step E4).
Ainsi, à un instant t quelconque, la station sol 2 reçoit un signal dont la puissance est réduite de la valeur de perte de gain causée par le dépointage total appliqué à l’instant t moins le temps de propagation de la liaison avec le satellite 3. Ce temps de propagation peut ne pas être totalement négligeable dans le cas de communications par satellite géostationnaire. Thus, at any instant t, the ground station 2 receives a signal whose power is reduced by the value of loss of gain caused by the total misalignment applied at instant t minus the propagation time of the link with the satellite 3 This propagation time may not be completely negligible in the case of geostationary satellite communications.
Les signaux reçus sont mesurés en puissance par l’unité radiofréquence 22 de la station sol 2 (étape E5) puis datés par son unité de traitement 23 à leur réception (étape E6). Cette datation a pour but de permettre un traitement d’ensemble de la courbe de variation de niveau stockée dans l’unité 24 après réception d’un cycle complet du mouvement. Pour pouvoir identifier la valeur de dépointage volontaire associé à une date de réception par la station sol 2, vu que le mouvement est une convention prédéfinie entre le terminal 1 et la station sol 2, il suffit alors simplement de connaître sa date d’émission dans la base de temps du terminal 1. The signals received are measured in power by the radio frequency unit 22 of the ground station 2 (step E5) then dated by its processing unit 23 on their reception (step E6). The purpose of this dating is to allow an overall processing of the level variation curve stored in the unit 24 after reception of a complete cycle of the movement. To be able to identify the voluntary depointing value associated with a date of reception by the ground station 2, since the movement is a predefined convention between the terminal 1 and the ground station 2, it is then sufficient simply to know its date of emission in the time base of terminal 1.
La station sol 2 connaît le mouvement de dépointage volontaire appliqué par l’ACU 12 du terminal 1 ainsi que leurs dates de déclenchement, dates identiques dans les deux bases de temps, du fait de l’étape de synchronisation (étape E1 ). La station sol 2 connaît aussi de manière déterministe la variation de niveau des signaux reçus en fonction de l’angle de dépointage effectif de l’antenne 11 du terminal 1. Ces connaissances sont obtenues par une mesure de référence du diagramme de rayonnement du lobe principal de l’antenne 11 à la qualification du modèle de terminal 1et sont stockées dans l’unité de stockage 23 de la station sol 2. On en déduit alors un gabarit de courbes de variation pendant le cycle de mouvement de dépointage volontaire qui est fonction du dépointage fortuit et des degrés de liberté dont dispose le terminal 1 comme, par exemple, l’amplitude globale du mouvement de dépointage. En particulier, pour chaque valeur du dépointage fortuit, on dispose d’une courbe typique de variation de la puissance des signaux tout au long du cycle de mouvement. The ground station 2 knows the voluntary depointing movement applied by the ACU 12 of the terminal 1 as well as their trigger dates, identical dates in the two time bases, due to the synchronization step (step E1). The ground station 2 also knows in a deterministic manner the level variation of the signals received as a function of the effective depointing angle of the antenna 11 of the terminal 1. This knowledge is obtained by a reference measurement of the radiation pattern of the main lobe of the antenna 11 to the qualification of the terminal model 1 and are stored in the storage unit 23 of the ground station 2. A variation curve template is then deduced therefrom during the voluntary depointing movement cycle which is a function of the accidental depointing and the degrees of freedom available to the terminal 1 such as, for example, the overall amplitude of the depointing movement. In particular, for each value of the fortuitous misalignment, we have a typical signal power variation curve throughout the movement cycle.
Alors, la variation de niveau du signal reçu est comparée avec le gabarit. De manière avantageuse, cette comparaison permet de sélectionner la valeur représentative, dépendante du dépointage fortuit, pour laquelle la variation de puissance du signal reçu ressemble le plus au gabarit (étape E7). Then, the level variation of the received signal is compared with the template. Advantageously, this comparison makes it possible to select the representative value, dependent on the fortuitous misalignment, for which the variation in power of the signal received most closely resembles the template (step E7).
En particulier, pour un dépointage total donné, la variation de puissance du signal reçu présente des maximas lorsque le dépointage volontaire est opposé à la direction de dépointage fortuit et des minimas lorsqu’il est dans la même direction. Le critère d’optimisation pour déterminer la valeur représentative du dépointage fortuit est, dans une réalisation préférée, une minimisation de l’erreur quadratique entre le gabarit et la mesure de niveau de puissance sur l’ensemble du cycle de mouvement. In particular, for a given total misalignment, the variation in power of the received signal exhibits maxima when the voluntary misalignment is opposite to the direction of the accidental misalignment and minima when it is in the same direction. The optimization criterion for determining the value representative of the fortuitous misalignment is, in a preferred embodiment, a minimization of the quadratic error between the template and the power level measurement over the entire movement cycle.
Par exemple, dans une réalisation préférée, le mouvement est circulaire et régulier autour de l’axe de visée effectif, d’une amplitude correspondant à x dB de réduction de gain du lobe principal symétrique de l’antenne 11 (dépointage de 0XCJB/2). Le gabarit est alors constitué de sinusoïdes et celle de plus grande ressemblance avec la courbe de variation de niveau est d’amplitude y dB et de phase <p, c’est-à-dire que le maximum à +y/2 dB se trouve à l’instant D.< /2ïT et le minimum à -y/2 dB à l’instant D.< /2TT+D/2 à partir du début du mouvement. Dans ce cas, le couple y et < /2ïT constitue une valeur représentative toute désignée permettant au terminal 1 de déterminer la valeur angulaire de son dépointage fortuit, dans sa convention de repère d’axe (au sens large, la valeur d’un m-uplet est constitué de m nombres). Alternativement, si le nombre x est aussi connu de la station sol 2, celle-ci peut déterminer elle-même la valeur de dépointage fortuit co et envoyer directement au terminal 1 la valeur de correction -œ à appliquer dans son repère d’axes. For example, in a preferred embodiment, the movement is circular and regular around the effective line of sight, with an amplitude corresponding to x dB of gain reduction of the symmetrical main lobe of the antenna 11 (shift of 0 X CJB /2). The template is then made up of sinusoids and the one most similar to the level variation curve has amplitude y dB and phase <p, i.e. the maximum at +y/2 dB is at instant D.< /2ïT and the minimum at -y/2 dB at instant D.< /2TT+D/2 from the beginning of the movement. In this case, the couple y and < /2ïT constitutes a representative value all designated allowing the terminal 1 to determine the angular value of its fortuitous depointing, in its axis reference convention (in the broad sense, the value of an m-tuple is made up of m numbers). Alternatively, if the number x is also known to the ground station 2, the latter can itself determine the fortuitous misalignment value co and send directly to the terminal 1 the correction value -œ to be applied in its axis coordinate system.
Dès lors, cette valeur représentative du dépointage fortuit est transmise au terminal 1 via l’unité radiofréquence 22 (étape E8) qui peut en déduire avec une bonne précision, la valeur angulaire du dépointage fortuit ainsi que de la valeur du dépointage effectif. Alors, le terminal 1 ajuste l’angle de son axe de visée effectif (étape E9) par une correction opposée. Le mouvement de dépointage volontaire (autour de l’axe de visée effectif 15) s’effectue désormais autour de lui. Consequently, this value representative of the fortuitous depointing is transmitted to the terminal 1 via the radiofrequency unit 22 (step E8) which can deduce therefrom with good precision the angular value of the fortuitous depointing as well as the value of the effective depointing. Then, the terminal 1 adjusts the angle of its effective line of sight (step E9) by an opposite correction. The intentional depointing movement (around the effective line of sight 15) now takes place around him.
Le procédé constitue ainsi une boucle d’asservissement tendant à rapidement annuler le dépointage fortuit et donc à faire correspondre l’axe de visée effectif 15 avec l’axe de visée attendu 13. The method thus constitutes a servo loop tending to quickly cancel the fortuitous misalignment and therefore to make the effective line of sight 15 correspond to the expected line of sight 13.
Si l’on interrompt le mouvement, l’antenne 11 du terminal 1 est alors parfaitement pointée puisque les dépointages fortuits et volontaires sont nuis. If the movement is interrupted, the antenna 11 of the terminal 1 is then perfectly pointed since the fortuitous and voluntary depointings are harmed.
Alternativement, lorsque la valeur angulaire du dépointage effectif calculée ou la variation maximale de niveau détectée sur une période de mouvement dépasse un seuil prédéfini, la station sol 2 peut donner instruction au terminal 1 de couper son émission (étape E10). Pour ce faire, la station sol 2 transmet au terminal 1 un ordre dans son protocole de signalisation de communication par satellite (non décrit ici). Alternatively, when the angular value of the calculated effective misalignment or the maximum variation in level detected over a period of movement exceeds a predefined threshold, the ground station 2 can instruct the terminal 1 to cut off its transmission (step E10). To do this, the ground station 2 transmits to the terminal 1 an order in its satellite communication signaling protocol (not described here).
De manière avantageuse, la mesure effectuée par la station sol 2 lors du procédé ne nécessite aucune communication, il suffit que le terminal 1 se soit initialement synchronisé dans les dizaines de minutes précédant le mouvement de dépointage volontaire. Elle peut être menée alors que le terminal émet une porteuse de niveau très faible sans émettre de données, ce qui peut constituer un mode dégradé de fonctionnement du terminal adopté pour ne mettre en péril ni les communications du système ni celles des satellites adjacents, alors que l’ACU 12 ou l’antenne 11 du terminal sont défaillants. Le système peut aussi convenir que, lorsque le terminal 1 ne reçoit pas ses données régulières de signalisation (incluant une correction de pointage parmi d’autres instructions) il bascule dans ce mode dégradé ou coupe son émission. La station est autonome pour prendre ces décisions, le système est alors rendu très fiable vis-à-vis des contraintes de la réglementation, alors même que le risque de défaillance du terminal 1 n’est pas négligeable. De manière complémentaire, la station sol 2 doit aussi mettre en oeuvre, de temps en temps, une vérification du pointage de son antenne au cours d’une procédure dédiée de « step track » qui l’amène aussi à légèrement dépointer son axe de visée de réception (étape E11 ). La procédure de pointage de l’antenne 21 de la station sol 2 requiert un dispositif de mesure du niveau de signal reçu dans l’unité radiofréquence 22. De manière avantageuse, cette même ressource est utilisée pour les deux procédures de mesure du dépointage effectif du terminal en émission et de la station en réception. Il faut alors s’assurer que ces procédures n’interfèrent pas mais aboutissent bien à des estimations de dépointage correctes. Advantageously, the measurement carried out by the ground station 2 during the method does not require any communication, it suffices that the terminal 1 is initially synchronized in the tens of minutes preceding the voluntary depointing movement. It can be carried out while the terminal is transmitting a very low level carrier without transmitting data, which may constitute a degraded mode of operation of the terminal adopted so as not to jeopardize either the communications of the system or those of the adjacent satellites, whereas the ACU 12 or the antenna 11 of the terminal are faulty. The system can also agree that, when the terminal 1 does not receive its regular signaling data (including a pointing correction among other instructions) it switches to this degraded mode or cuts its transmission. The station is autonomous to take these decisions, the system is then made very reliable vis-à-vis the constraints of the regulations, even though the risk of failure of the terminal 1 is not negligible. In addition, the ground station 2 must also implement, from time to time, a verification of the pointing of its antenna during a dedicated "step track" procedure which also leads it to slightly depoint its line of sight reception (step E11). The procedure for pointing the antenna 21 of the ground station 2 requires a device for measuring the signal level received in the radiofrequency unit 22. Advantageously, this same resource is used for the two procedures for measuring the effective depointing of the terminal in transmission and the station in reception. It must then be ensured that these procedures do not interfere but lead to correct depointing estimates.
De manière avantageuse, les cycles de dépointage pour le terminal 1 et la station au sol 2 peuvent être multiplexés dans le temps pour éviter qu’ils aient lieu simultanément. Il est également possible d’effectuer le mouvement de dépointage du terminal au sein d’une plage de dépointage fixe de la procédure de « step track » de la station au sol 2. D’une manière générale, il suffit que la station veille à modifier le pointage de son antenne uniquement en dehors des cycles du mouvement de dépointage de l’antenne 11. Les intervalles de temps au-delà de la durée D du mouvement jusqu’à la reprise du cycle suivant de dépointage peuvent être mises à profit dans ce but. Advantageously, the depointing cycles for the terminal 1 and the ground station 2 can be multiplexed in time to prevent them from taking place simultaneously. It is also possible to carry out the depointing movement of the terminal within a fixed depointing range of the "step track" procedure of the ground station 2. In general, it is sufficient for the station to ensure that modify the pointing of its antenna only outside the cycles of the antenna depointing movement 11. The time intervals beyond the duration D of the movement until the resumption of the following depointing cycle can be used in this goal.
De manière complémentaire, lorsque l’antenne du terminal 1 présente un diagramme asymétrique, afin qu’une variation de niveau puisse être traduite en angle de dépointage, la convention de repère d’axes est préférablement alignée avec les directions de plus grande et plus petite directivité du diagramme de rayonnement. Dans ce cas, la station sol 2 peut traduire les variations de niveaux en dépointage fortuit puisque le diagramme d’antenne est également défini dans ce repère. Elle n’a alors pas besoin de connaitre l’angle de biais (en anglais, skew) pour déterminer le dépointage dans chaque direction principale de l’antenne (de plus grande et plus petite directivité). Les consignes de correction de pointage sont alors également renvoyées dans ce repère qui est bien évidement connu de l’ACU 12. In a complementary manner, when the antenna of terminal 1 has an asymmetrical pattern, so that a variation in level can be translated into a depointing angle, the axis reference convention is preferably aligned with the directions of greater and lesser directivity of the radiation pattern. In this case, the ground station 2 can translate the level variations into fortuitous misalignment since the antenna pattern is also defined in this frame. It then does not need to know the angle of bias (in English, skew) to determine the misalignment in each main direction of the antenna (of greater and lesser directivity). The pointing correction instructions are then also sent back to this reference which is of course known to the ACU 12.

Claims

REVENDICATIONS
1. Procédé de contrôle d’une antenne (11 ) d’émission d’un terminal (1 ) en connecté avec une station sol (3), l’antenne (11 ) pointant soit vers la station sol (3), soit vers un satellite (3) configuré pour relayer un signal issu de l’antenne vers la station sol (3) selon un axe de visée effectif (15), ledit procédé comprenant les étapes suivantes mises en oeuvre dans une unité (12) de contrôle d’antenne du terminal (1 ) : 1. A method of controlling an antenna (11) transmitting from a terminal (1) connected to a ground station (3), the antenna (11) pointing either towards the ground station (3) or towards a satellite (3) configured to relay a signal from the antenna to the ground station (3) along an effective line of sight (15), said method comprising the following steps implemented in a control unit (12) antenna of the terminal (1):
- synchronisation (E1 ) d’une base de temps du terminal (1 ) avec une base de temps d’une station sol (2), ladite station sol étant configurée pour être en communication avec le terminal (1 ) ; - synchronization (E1) of a time base of the terminal (1) with a time base of a ground station (2), said ground station being configured to be in communication with the terminal (1);
- déclenchement (E2) à une date prédéterminée dans la base de temps du terminal (1 ) synchronisée d’un cycle de mouvement de dépointage volontaire de l’antenne d’émission (11 ) de manière à faire varier l’axe de visée effectif (15) selon un axe de visée courant (14) variable au cours dudit cycle ; - triggering (E2) on a predetermined date in the time base of the terminal (1) synchronized with a voluntary depointing movement cycle of the transmitting antenna (11) so as to vary the effective line of sight (15) along a current line of sight (14) variable during said cycle;
- émission (E3) par l’antenne (11 ) du terminal (1 ) d’un signal vers la station sol (2) au cours dudit cycle de dépointage selon ledit axe de visée courant (14) variant selon ledit cycle ; - transmission (E3) by the antenna (11) of the terminal (1) of a signal to the ground station (2) during said depointing cycle along said current line of sight (14) varying according to said cycle;
- réception (E8) à la fin dudit cycle, d’un signal émis par la station sol (2), ledit signal comprenant une valeur représentative à partir de laquelle le terminal (1 ) peut en déduire l’angle de dépointage fortuit défini entre l’axe de visée effectif (15) et l’axe de visée attendu (13) ; - reception (E8) at the end of said cycle, of a signal emitted by the ground station (2), said signal comprising a representative value from which the terminal (1) can deduce therefrom the fortuitous depointing angle defined between the effective line of sight (15) and the expected line of sight (13);
- correction (E9), de l’axe de visée effectif (15) de l’angle de dépointage fortuit, de manière à ce que l’axe de visée effectif (15) soit aligné avec l’axe de visé attendu (13). - correction (E9), of the effective line of sight (15) of the accidental misalignment angle, so that the effective line of sight (15) is aligned with the expected line of sight (13) .
2. Procédé selon la revendication 1 , dans laquelle la date de déclenchement prédéterminée se répète selon une séquence connue à la fois du terminal (1 ) et de la station sol (2) 2. Method according to claim 1, in which the predetermined trigger date is repeated according to a sequence known to both the terminal (1) and the ground station (2)
3. Procédé selon la revendication 1 ou 2, dans laquelle le cycle de mouvement connu du terminal (1 ) et de la station sol (2). 3. Method according to claim 1 or 2, in which the known movement cycle of the terminal (1) and of the ground station (2).
4. Procédé selon l’une des revendications précédentes, comprenant en outre les étapes suivantes mises en oeuvre par la station sol (2) : - réception (E4) de signaux émis par le terminal (1 ) au cours du mouvement de dépointage volontaire autour d’un axe de visée effectif (15) de l’antenne (11 ) vers le satellite ou la station sol (2) ; 4. Method according to one of the preceding claims, further comprising the following steps implemented by the ground station (2): - reception (E4) of signals emitted by the terminal (1) during the voluntary depointing movement around an effective line of sight (15) of the antenna (11) towards the satellite or the ground station (2);
- mesure du niveau de réception du signal (E5) ; - measurement of the signal reception level (E5);
- datation (E6) de la courbe de niveau de réception de signal selon la base de temps de la station sol (2) ; - Dating (E6) of the signal reception level curve according to the time base of the ground station (2);
- détermination (E7) à partir de la courbe de niveau, d’une valeur représentative du dépointage fortuit de l’antenne d’émission du terminal ; - determination (E7) from the level curve, of a value representative of the accidental misalignment of the terminal's transmission antenna;
- transmission (E8) de cette valeur représentative ainsi déterminée au terminal de manière à ce qu’il détermine son angle de dépointage fortuit et corrige l’axe de visée effectif de l’antenne (11 ). - transmission (E8) of this representative value thus determined to the terminal so that it determines its accidental misalignment angle and corrects the effective line of sight of the antenna (11).
5. Procédé selon la revendication 4, dans laquelle la détermination (E7) d’une valeur représentative du dépointage fortuit comprend les étapes de : 5. Method according to claim 4, in which the determination (E7) of a value representative of the fortuitous depointing comprises the steps of:
- comparaison de la variation de niveau du signal reçu avec un gabarit de courbes dépendantes du dépointage fortuit de l’antenne du terminal ; - comparison of the level variation of the signal received with a template of curves dependent on the fortuitous depointing of the antenna of the terminal;
- sélection d’une valeur représentative désignant la courbe du gabarit présentant la plus grande ressemblance avec une variation de niveau du signal reçu. - selection of a representative value designating the curve of the template presenting the greatest resemblance to a variation in the level of the received signal.
6. Procédé selon l’une des revendications précédentes, dans lequel le mouvement de dépointage angulaire est circonscrit dans le lobe principal de rayonnement de l’antenne du terminal. 6. Method according to one of the preceding claims, in which the angular depointing movement is circumscribed in the main radiation lobe of the antenna of the terminal.
7. Procédé de contrôle d’une antenne selon l’une des revendications précédentes, comprenant une étape (E10) de commande de coupure de l’émission du terminal par la station sol lorsqu’elle détecte une variation de niveau ou un dépointage angulaire supérieurs à un seuil déterminé. 7. Method for controlling an antenna according to one of the preceding claims, comprising a step (E10) of controlling the transmission of the terminal by the ground station when it detects a level variation or an angular misalignment greater at a certain threshold.
8. Procédé de contrôle d’une antenne selon la revendication 4, dans laquelle la station sol est configurée pour procéder à des séquences de réalignement de son antenne (21 ) de réception en utilisant aussi une méthode de mesure du niveau de signal par l’unité radiofréquence qui effectue la mesure de niveau reçu (E5) lors du contrôle de l’antenne (11 ) du terminal (1 ).; 8. Method for controlling an antenna according to claim 4, in which the ground station is configured to carry out sequences of realignment of its receiving antenna (21) also using a method of measuring the signal level by the radiofrequency unit which performs the received level measurement (E5) when checking the antenna (11) of the terminal (1);
9. Procédé de contrôle d’une antenne selon la revendication 8, pour laquelle la station sol ne s’autorise à modifier le pointage de son antenne qu’entre les cycles de mouvement prédéfinis de l’antenne du terminal. 9. Method for controlling an antenna according to claim 8, for which the ground station is only authorized to modify the pointing of its antenna between the predefined movement cycles of the antenna of the terminal.
10. Procédé de contrôle selon l’une des revendications précédentes, dans lequel la base de temps du terminal est corrigée du temps de propagation du signal du terminal à la station. 10. Control method according to one of the preceding claims, in which the time base of the terminal is corrected by the propagation time of the signal from the terminal to the station.
11. Système comprenant au moins une station sol et au moins un terminal, ledit système étant configuré pour mettre en oeuvre un procédé selon l’une des revendications précédentes. 11. System comprising at least one ground station and at least one terminal, said system being configured to implement a method according to one of the preceding claims.
PCT/FR2022/050094 2021-01-28 2022-01-18 Method and system for controlling an antenna in a satellite communication system WO2022162294A1 (en)

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Citations (5)

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Publication number Priority date Publication date Assignee Title
EP0624804A1 (en) * 1993-05-14 1994-11-17 Alcatel Telspace Tracking system for estimating the pointing error of a HF antenna
US6433736B1 (en) * 2000-11-22 2002-08-13 L-3 Communications Corp. Method and apparatus for an improved antenna tracking system mounted on an unstable platform
US20080143622A1 (en) * 2006-12-13 2008-06-19 The Boeing Company Method and apparatus for precision antenna boresight error estimates
FR3070548A1 (en) * 2017-08-30 2019-03-01 Zodiac Data Systems METHOD AND DEVICE FOR ESTIMATING ANTENNA DEPARTMENT AND METHOD AND DEVICE FOR PURSING ANTENNA POINTING USING SUCH A METHOD AND DEVICE BASED ON HARMONIC ANALYSIS
EP3654549A1 (en) * 2018-11-15 2020-05-20 Thales Method and device for conserving the pointing of an antenna with a satellite

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0624804A1 (en) * 1993-05-14 1994-11-17 Alcatel Telspace Tracking system for estimating the pointing error of a HF antenna
US6433736B1 (en) * 2000-11-22 2002-08-13 L-3 Communications Corp. Method and apparatus for an improved antenna tracking system mounted on an unstable platform
US20080143622A1 (en) * 2006-12-13 2008-06-19 The Boeing Company Method and apparatus for precision antenna boresight error estimates
FR3070548A1 (en) * 2017-08-30 2019-03-01 Zodiac Data Systems METHOD AND DEVICE FOR ESTIMATING ANTENNA DEPARTMENT AND METHOD AND DEVICE FOR PURSING ANTENNA POINTING USING SUCH A METHOD AND DEVICE BASED ON HARMONIC ANALYSIS
EP3654549A1 (en) * 2018-11-15 2020-05-20 Thales Method and device for conserving the pointing of an antenna with a satellite

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