FR2578058A1 - METHOD AND DEVICE FOR PURSUING A COMMUNICATION SATELLITE - Google Patents

Abstract

THIS DEVICE IS CHARACTERIZED IN THAT IT INCLUDES: A PRIMARY AUXILIARY RADIANT ELEMENT 16 LOCATED NEAR THE MAIN RADIANT ELEMENT 16 SO AS TO PRESENT A SLIGHT DIFFERENCE OF AZIMUTH FROM THE AUDIT REPORT MAIN RADIANT ELEMENT; AN AUXILIARY LEVEL DETECTOR 26, AUDIT TORQUE OF THE AUXILIARY PRIMARY RADIANT ELEMENT, SO AS TO DETECT AN AUXILIARY SIGNAL LEVEL RECEIVED BY ITS AUXILIARY RADIANT ELEMENT; SECOND COMMAND MEANS 22, ACTING IN RESPONSE TO THE DIFFERENCE IN THE LEVELS OF THE MAIN AND SECONDARY SIGNALS, SO AS TO MAKE A FIRST DRIVE UNIT 12 TO MODIFY THE AZIMUTH OF THE SAID ANTENNA, SO THAT THIS DIFFERENCE SHOWS A PREDETERMINALITY, AND THE THIRD CONTROL MEANS 24, ACTING IN RESPONSE TO THE DIFFERENCE IN THE LEVELS OF THE MAIN AND AUXILIARY SIGNALS SO AS TO CAUSE THE FIRST DRIVE UNIT TO CHANGE THE AZIMUTH OF THE SAID ANTENNA, WHEN THIS SIGNAL LEVEL LOWER FROM THE MAIN PREDETERMINED LEVEL, SO THAT THIS MAIN SIGNAL LEVEL EXCEEDS ITS PREDETERMINED LEVEL.

Description

1 2578058

  The present invention relates to a device and a method for tracking a communication satellite using a satellite dish placed on a mobile, for example a ship, in order to efficiently receive a

  electric wave emanating from this communication satellite, automatically modifying

  the elevation and azimuth of the antenna in response to the movement of the mobile. Generally, a satellite dish used for the pursuit of a communication satellite and which is installed on a mobile such as a ship or a floating platform, is provided with elevation control means and azimuth, detection means of the invention. elevation and azimuth, means for detecting the inclination of the mobile in the direction of elevation, means for detecting the level of the received signals, and means for controlling the means

  drive and control in elevation and azimuth according to a

  predetermined gram, which is based on tilt, azimuth and elevation

  and on the data relating to the level of the received signals.

  This licensee has already described a perfect ordering program

  for the means of elevation and azimuth drive of an aircraft system.

  French Patent No. 85 07 881, filed May 24, 1985. In such a program, the antenna begins to scan the entire azimuth around a

  reference or departure elevation, which is obtained from a table dis-

  available for this purpose until the level of the signals

  it exceeds a first reference level. Then, the antenna is controlled so that its axis describes a rectangular spiral on the celestial sphere, until the level of the received signals exceeds a second reference level, which is higher than the first reference level. The spiral scanning search is repeated as a correction search when the level of the received signals falls below the value of the second reference level,

  due to the displacement of the mobile on which the antenna is positioned.

  The search for spiral correction is performed in relation to the di-

  origin for which the maximum signal level has been obtained. In

  in other words, this search is carried out in such a way as to cover the same

  azimuth on each side of the original direction, although the direction

  of the target may have changed to one of the signs of the azimuth. As a result

  that, if the sign of the azimuth change in direction of the target can be detected, it is possible to double the efficiency of the search by limiting

the latter to the detected sign.

  The subject of the invention is therefore an improved method of tracking a communication satellite using a parabolic antenna mounted on a moving body, for example a ship, which makes it possible to improve

  important the accuracy of the pursuit, according to the principles mentioned above.

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  Another object of this invention is a new device for

  implementation of the method mentioned above.

  According to this invention, therefore, a device is provided for automatically ensuring the tracking of a communication satellite by means of a parabolic antenna, which comprises a parabolic reflector, a beam element

  the primary focus of this reflector, a first training unit

  to rotate said antenna about its azimuth axis, a second

  drive unit for rotating this antenna about its axis of elevation.

  a main level detector, coupled to said primary primary radiating element for detecting a primary signal level received by the element

  radiating principal, and first control means acting in response to

  said primary signal level to cause said first and second drive units to operate said antenna so that the main signal level exceeds a predetermined level, which device is characterized in that

  it includes: an auxiliary primary radiating element located near

  radiating principal so as to have a slight difference in azimuth with respect to said main radiating element; an auxiliary level detector,

  coupled to said auxiliary primary radiating element so as to detect a

  auxiliary signal caliber received by said auxiliary radiating element; se-

  control means, acting in response to the difference in the levels of the

  primary and secondary signals, so as to bring the first unit of

  dragging to modify the azimuth of said antenna, so that this difference

  has a predetermined polarity, and third control means

  in response to the difference in the levels of the main and auxiliary signals,

  in order to cause the first training unit to change the azimuth of the

  said antenna, when said main signal level falls below said predetermined level, so that this main signal level exceeds said predetermined level.

  Other features and advantages of the present invention are

  the description given below with reference to the accompanying drawings, which

  illustrate an example of embodiment devoid of any limiting character.

On the drawings:

  FIG. 1 is a block diagram illustrating a summary of the principal

  components of the device of this invention;

  FIG. 2 is a block diagram showing an exemplary embodiment of

  tion of a device object of this invention; - Figures 3a and 3b are diagrams for illustrating an embodiment of a program for carrying out the method object of this invention; - Figure 4 is a diagram illustrating the characteristic curves of the main and secondary radiating elements to better understand the invention; and, FIGS. 5 and 6 are diagrams representing the two tracking tracks which are drawn during the execution of the program illustrated in FIG. 3.

  Referring first to Figure 1, it can be seen that the device ob-

  of this invention comprises a parabolic antenna 10, mechanically coupled

  first and second drive means 12 and 14, for respectively moving the antenna 10, relative to its azimuth axis and its axis of elevation. The satellite dish 10 is provided with a pair of elements

  similar primary radiators 16, 16 ', mounted relative to the body of the

  tenne using a frame or a suitable support arm, not shown.

  The first élémentrayonnant 16, which will be designated hereinafter main radiating element, is located at the focus of the parabolic antenna 10, and is oriented towards its axial direction, while the second radiating element 16 'designated

  hereinafter auxiliary radiating element, is located near the radiating element

  principal number 16, but is slightly shifted in the direction of azi-

  muth. The signals that are received by the radiating elements 16 and 16 'pre-

  frequencies that are appropriately converted into con-

  frequency invertors 18, 18 ', and are respectively supplied to main and auxiliary level detectors 26 and 26'. The main level detector 26 detects the level of the main input signal, and delivers a signal indicating the level corresponding to first, second and third control means, 20, 22 and 24, while the auxiliary level detector 26 detects the secondary input signal level, and provides a signal indicative of the level corresponding to the second and third control means 22 and 24. The first control means 20, which are commonly used in prior art devices, act in response at the level

  current signal, so as to deliver a control signal to the

  first and second drive means 12 and 14 for orienting the antenna so that the main signal level exceeds a predetermined level. The second control means 22, which are specific to the device of the present invention, act in response to the levels of the main and secondary signals so as to deliver a second control signal to the first drive means 12, to modify the azimuth of the antenna 10, so

  difference between the levels of the main and secondary signals

  feels a predetermined polarity. The third control means 24, which are also specific to the device that is the subject of the present invention, act in response to the difference in the levels of the main and secondary signals,

  in order to deliver a third control signal to the first

  12, in order to change the azimuth of the antenna 10, so that the main signal level exceeds the predetermined level when this level is lowered

  below said predetermined level.

  Although, in FIG. 1, the control means 20, 22 and 24 have been

  represented in separate units, in practice they can be

  in the form of a single set, consisting for example of a micro-

  computer, as described below with reference to the exemplary embodiment

illustrated in Figure 2.

  In this FIG. 2, there is shown a parabolic antenna 10 receiving an electric wave coming from a broadcasting satellite (not shown), this antenna being mounted on a platform 32, fixed to a mobile body (not shown), by example a ship. The antenna 10 is designed so that it can

  be rotated about a horizontal axis, to undergo changes

  by means of an elevating drive unit 36, and

  around a vertical axis to undergo azimuth changes using an azimuth drive unit 38. Training units 36 and 38

  are respectively controlled, in angle and in direction of rotation, with the aid of

  The drive units 36 and 38 may be embodied as electric motors, controlled by switching systems, such as the control units 40 and 42, or alternatively by the control units 40 and 42. they can be made in the form of hydraulic cylinders, controlled by electromagnetic valve systems. Elevation and azimuth detectors 44 and 46 are respectively coupled to the elevation and azimuth drive units 36 and 38 to sense the magnitude and direction of variation of elevation and azimuth. from a selected reference direction of the antenna 10, to respectively produce elevation and azimuth signals VEL and VAZ. The detectors 44 and 46 can be made, for example, in the form of potentiometers. An inclination sensor 48 is coupled to a second platform 34, driven by the drive unit.

  azimuth 38, and designed to detect the amplitude and direction of inclination.

  sound of this platform 34 in a vertical plane passing through the axis of the para-

  10 to produce a VINC tilt signal. The inclination detector

  its 48 may include orthogonal levels.

  The antenna 10 is provided with a pair of primary radiating elements 16 and 16 ', which are arranged, with respect to the parabolic antenna 10, as described above with reference to FIG. 1. In this example it is assumed that the auxiliary radiating element 16 'is deflected to the left from the main radiating element 16, as shown in the drawing, when looking at the Figure from the front of the antenna. The main radiating element 16 is coupled to a main tuner (tuner) 52, via a frequency converter 18, and the auxiliary radiator 16 'is coupled to an auxiliary tuner ( tuner) 52 'by

  via a frequency converter 18 '. Frequency converters

  18 and 18 'transform a microwave frequency from the satellite

  communication in a low frequency signal. The main agreement mechanism

  cipal 52 reconverts this low frequency signal into an optimal frequency signal.

  male for a conventional television receiver 54, and it also detects the

  input signal, so as to produce a main level signal M, which in-

  the signal level currently received by the main radiating element

  The auxiliary tuning device 52 'detects the input signal

  of the converter 18 ', so as to produce a secondary level signal S, providing an indication of the level of signal received routinely by

  the auxiliary radiating element 16 '.

  The signals M, S, VEL, VAZ, VINC are delivered to an analog converter

  number 58 via an input regulator 56, and are thus transformed, in a digital form, allowing their processing in a

  central processing unit 60, for example in the form of a micro-

  computer, as described below with reference to Figures 3 and following.

  The central processing unit 60 delivers a set of control signals, in order to control the elevation and azimuth of the antenna 10, via a drive unit 62, to ensure the control of amplification and level. The output of the control unit 62 is divided into control signals K'EL and K'Az via a solid state relay 64, and these signals are transformed into KEL DC control signals. and KAZ, using a rectifier 66, and are respectively applied to the elevation and azimuth control units 40 and 42. The central processing unit 30 is provided with

  of a keyboard or a digital switch 68 for the introduction of an op-

  of the elevation, as described below.

  Reference is now made to Figures 3a and 3b, which illustrate the method of tracking a communication satellite according to the present invention. The

  first step of this process is to correctly orient the parabolic antenna

  to the satellite, so as to receive signals at a maximum level of

  when the platform 32 is in the fixed state (for example, when the ship

supporting the antenna is stopped).

  In step 100, an initial value 90 of the elevation angle θ is written into the central processing unit 60 using the digital switch 68. This value 00 represents the approximate altitude of the satellite for the the ship's geographical position, and it can be obtained from commercially available charts or maps. During this

  step 100, one also inscribes in the central unit 60: X = 1, and N = 2X - 1.

  X and N are variables expressed in degrees. In the next step 102, the uni-

  60 and the following control system are actuated so as to

  the antenna 10 is brought to its predetermined azimuth direction O, at the step 104 (<= 0). Then, during the step 106, the antenna 10 is turned successively to the right, in order to increase the value of the azimuth Y, and, if necessary, when

  of step 108, when the signal level M exceeds a predetermined level or not

  mine. If this is not the case, we then search if the azimuth t has

  stained or not 360 in step 110. Otherwise, steps 106, 108 and 110 are repeated, and when the azimuth has reached 360, the elevation of the antenna 10 is changed to 0 = O + 0.5 N degrees, in step 112. In this case, N = 1, since X = 1, and therefore the new value of

  the elevation Q = 0 + 0.5 degree. This means that the axis of the antenna 10 has

  written a trace 0-1-2, as shown in Figure 5, on the celestial sphere,

during steps 104 to 112.

  In the next step 114, the antenna 10 is turned successively in the opposite direction, that is to say to the left. During this revolution in azimuth, it is sought, in step 116, if the signal level M exceeds

  or not the value r and, in step 118, if the value of the azimuth has reverted to

  whether the azimuth is returned to O before the signal level M reaches the value P, the elevation 0 of the antenna 10 has decreased by X, which in this case is equal to 1, in step 120, and the value of X is then increased by one degree, and thus becomes two degrees in step 122. It is understood that the trace of the antenna 10 on the celestial sphere is

  from point 2 to point 4 during the execution of steps 112 to 122.

  In the next step 124, it is investigated whether or not the value of X has reached 5, and if it is not the case, the process returns to step 106, and the direction of the azimuth revolution of the Antenna 10 changes, and similar steps are repeated until the value X reaches 5. When X has reached the value of 5, the antenna has reached the end point 19 of its trace on the celestial sphere, as shown in FIG. 5, and the process returns to its starting point, in order to correct the initial value of When the signal level M has exceeded the value P during step 108 or step 116, the process proceeds to the correction phase, which starts at step 126. During this phase of correction, the secondary signal level S is used at the same time as the main signal level M. As seen in Figure 4, the characteristic curves of the radiating elements 16 and 16 'are substantially identical, but they are slightly

7 2578058

  offset in the horizontal direction. The predetermined level mentioned above

  A is a signal level allowing a comfortable reception of

  emissions from the satellite, and the value of this level is chosen slightly

  below the intersection of the M and S characteristic curves.

  the difference M - S is close to 0 or positive when the main signal level M is greater than the value d (for the domain A represented in FIG. 4). As can be seen in Figure 4, there are two inadmissible domains E and D in which the main signal level M is less than the value. Similarly, as seen in the drawing, the difference M - S is negative in the domain E, while it is positive in the domain D. In other words, when the main signal level M falls below the value, the antenna 10 is deflected to the left of the satellite when M - S is negative, and this antenna is deflected to the right when M - S is

  positive. The method of this invention uses this feature.

  Returning now to Figure 3a. In step 126, it is searched whether the value M - S is positive (including Q) or not, that is to say if the satellite

  is or is not located in domain C (Figure 4). If the answer is NO, this means

  whether the satellite is located inside domain B or domain E (if we are sure that M is greater than 0, the satellite is located in the domain

  B). Therefore, in order to correct the value of the azimuth, the antenna is rotated.

  born to the left during the step 131, and it is searched if M is greater than or not. This search is also performed for confirmation when the answer is YES in step 126. If confirmation is obtained,

  step 128, that M is greater than, the antenna is stopped in step 130.

  After stopping the antenna, during step 130, it is again checked whether M - S is positive or not. If the answer is NO, the antenna is turned to the left during step 136, as in step 131, and in step 128, a reconfirmation is obtained that M is greater than e. If the answer is YES, the current level a of the inclination signal VINC is written in the central unit 60, and then, the steps 128, 130 and 132. are executed in the same way. During this repetition of steps 128 to 136, the antenna captures the satellite in the

  desired domain C, shown in Figure 4.

  If, on the contrary, in the above steps, the antenna has not caught up with the satellite in area A of Figure 4, as a result of the movement of the ship,

  the answer becomes NO in step 128, and step 138, illus-

  shown in Figure 3b. In step 138, it is searched whether the difference M S is positive, zero or negative. If it is positive, this means that the satellite is located in the domain D, and, therefore, the antenna is turned to the right in step 140, and step 142. If M-S is negative, this

  means that the satellite is located in the E domain (Figure 4), and, by way of

  the antenna is turned to the left during step 144, and

  step 142. If the difference in levels M - S = 0, step 142 is executed directly (when the characteristic curves M and S have the relationship shown in FIG. 4, with respect to the level f, the difference M - S never becomes O when M is less than I. However, such a probability M - S = O, and at the same time M.C, can be obtained when the ship leaves the transmission zone. , or that it is located in the shadow area of an Island and that the levels of the received signals have become too

low).

  In step 142, the current level b of the inclination signal VINC is written in the central unit 60, and in step 146, it is searched whether

  the difference a - b is positive, zero, or negative. This difference represents

  a difference in elevation of the antenna with respect to the desired value, in

  step 134, as a result of the roll and / or pitch of the vessel supporting the antenna.

  If the difference is positive, this means a decrease in the elevation, and therefore the value O of the elevation is increased in step 140, and

  step 150 is then executed. If this difference is negative, this means

  an increase in the elevation, and therefore the value of the elevation is reduced in step 152 and step 150 is performed.

  is zero, this means that there is no deviation from the de-

  of the elevation, and therefore we proceed directly to the next step

  150. In this step 150, it is searched whether or not M is greater than / If the value is YES, this means that the satellite is located in the domain C of FIG. 4, and therefore the program returns to the step 128, of

  to repeat the steps mentioned above.

  The program described above gives satisfaction under conditions

  normal reception conditions, in the case where the intersection of the two characteristic curves

  above the predetermined level (Figure 4), that is, when the main signal level M falls below level i, the antenna can be turned to the right as long as the difference M - S is positive, however, when the received signal level has

  experienced an extraordinary fall, for some reasons, of the type mentioned

  above, the intersection of the two characteristic curves is then below the level, as represented by '(relatively). In such a condition, optimal reception can not be obtained by turning the antenna to the right when the satellite is in the domain F of FIG. 4, although the difference M - S is positive. As a result, if the answer,

  in step 150, is NO, it is necessary to execute a special program, such as

hereinafter.

  In step 154, the value of X is reduced to 1, and in step 156, the antenna is shifted to the right, so as to increase its azimuth. In the next step 158, it is checked whether the level of the main signal M has reached the level. If the answer is YES, the program is returned to step 128, and the steps mentioned above are repeated, so as to maintain the optimum condition for reception. However, if the answer is NO, it is sought, in step 160, whether or not the increment of the azimuth has reached the value of 5, and steps 156, 158 and 160 are repeated until

  that this increment & reaches 5. When this increment reaches 5, the

  the antenna is increased by 0.5 N degrees, ie 0.5 degrees in this case, since N = 2X - 1, and X = 1, this operation being performed

  in step 162. Then, the antenna is turned in the opposite direction, that is,

  say to the left-in order to decrease the value of the azimuth-in the step-

  164 and it is still sought if the level M has reached or not the value P, in step 166. If the answer is YES, the program is returned to step 128, and the steps mentioned above are repeated. above to maintain these reception conditions. If the answer is NO, then it is sought, in step 168, whether the decrement of azimuth z'f has reached 5, that is to say if the antenna has turned to the left of 10 from of step 164, or not, and steps 164, 166 and 168 are repeated until such azimuth is reached. When this azimuth is reached, the elevation of the antenna is reduced by X degrees, in step 170, that is to say, in this case, by one degree. Then, the value of X is increased by one degree in the step 172, and it is investigated whether or not X has reached 5, in the step 174. If the answer is NO, the program is returned to the step 156, and steps 156 to 174 are repeated in the same way, until the value of X reaches 5. We understand that when the value of X has

  reached 5, the axis of the antenna has described, on the celestial

  Figure 6. As can be seen in the drawing, this search is performed over a range of 10 azimuth from the initial direction, y

  included on the left side, to avoid the defect mentioned above.

  When the value of X reaches 5 in step 174, this means that the satellite has deflected too much to allow correction of the error, and therefore the program is brought back to the starting point,

  to re-determine the initial value of elevation 00.

  It remains understood that this invention is not limited to the embodiments described or represented, but encompasses all

the variants.

2578058

Claims (3)

  1 - Device for automatically ensuring the continuation of a   satellite communication using a satellite dish, which includes a   parabolic reflector, a primary radiating element placed at the focus of this   a first drive unit for rotating said antenna about its azimuth axis, a second drive unit for   this antenna around its elevation axis, a main level detector   pal, coupled to said primary primary radiator for detecting a   the main signal level received by the main radiator, and   first control means acting in response to said main signal level   to cause said first and second drive units to actuate the   said antenna so that the main signal level exceeds a pre-   determined, this device being characterized in that it comprises: an element   auxiliary primary radiator (16 '), located near said primary radiating element   pal (16), so as to have a slight difference in azimuth with respect to said main radiating element; an auxiliary level detector (26 '), coupled to said auxiliary primary radiator element for detecting an auxiliary signal level received by said auxiliary radiator; second control means (22) acting in response to the difference of the levels of the   primary and secondary signals, so as to bring the first unit of   (12) to modify the azimuth of said antenna, so that this difference   a predetermined polarity, and third control means (24), responsive to the difference in the levels of the main and   auxiliary, so as to cause the first training unit to change the azimuth   muth of said antenna when said main signal level drops below   below said predetermined level, so that this main signal level ex- yields said predetermined level.   2 - Device according to claim 1, characterized in that said first, second and third control means (20, 22, 24) are incorporated   in a single microcomputer (60).   3 - Method for automatically providing tracking of a communication satellite using a satellite dish which comprises a reflector   parabolic, a main radiating element placed at the focus of this reflector pa-   a primary auxiliary radiating element placed close to said main radiating element so as to have a slight difference in azimuth   relative to the main radiator, and primary level detectors   cipal and secondary, respectively coupled to the main and auxiliary radiators, to detect the main and auxiliary signal levels received respectively by the main and auxiliary radiators, which   characterized in that it consists in: adjusting the azimuth and elevation   of said antenna so as to allow said main signal level   to exceed a predetermined level; set the azimuth of said antenna to   wherein the difference between the main signal level and the auxiliary signal level has a predetermined polarity, and adjust the azimuth of said antenna when the main signal level has fallen below said predetermined level, depending on the polarity of said said difference in levels of   signals, thereby restoring the predetermined signal level.