CA2325355A1 - Method for homing in on a selected satellite, and a controller for orienting a rotatable antenna - Google Patents

Abstract

A method is disclosed for homing in on a selected satellite from a predetermined geographic location whose geographic coordinates are known, with an antenna that is rotatably supported for rotation in a respective horizontal and vertical plane. The electromagnetic power received in the receive direction is compared with an optimally possible satellite power known for the selected satellite. If the received electromagnetic power is different from the optimally possible satellite power of the selected satellite, then the antenna is rotated in a direction where the received power is greater. Also disclosed is a controller for orienting a rotatable antenna with respect to an electromagnetic radiation source of a satellite.

Description

1 METHOD FOR HOMING !N ON A SELECTED SATELLITE, AND A

2 CONTROLLER FOR ORIENTING A ROTATABLE ANTENNA

3

4 CROSS~REFERENCES TO RELATED APPLICATIONS
6 This application claims the priority of German Patent Application Serial 7 No. 199 54 .531 _6, filed November 12, 1999, the subject matter of which is 8 incorporated herein by reference.

",0 BACKGROUND OF THE INVENTION

12 The present invention relates to a method for homing in on a selected 13 satellite from a predetermined geographic location whose geographic 14 coordinates are known, with an antenna that is rotatabiy supported for rotation in a respective horizontal and vertical plane. The invention also relates to a 16 controller for orienting a rotatable antenna with respect to an electromagnetic 17 radiation source of a sateffite_ 19 Antennas for receiving electromagnetic radiation from a transmitter that is part of a satellite positioned at a specified location in an orbit has become 21 increasingly important. An antenna capable of receiving a signals that are 22 transmitted by the transmitter of the satellite can be used to monitor events that 23 occur over a wide area on the Earth surface, for example traffic patternsSuch ~m0~d d9~:v0 00izeiii e~zz~t~zziz ~~~ N~sma3m~ w ,~aN~H
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1 an antenna can alsa be used to receive television programs transmitted by the 2 transmitter. A rotatable antennas can be oriented with respect to the transmitter 3 so as to receive an optimal power level radiated by the transmitter. For this purpose, a controller has to be provided that can generate control signals and transmit these control signals to drives that rotate the antenna in an horizontal 6 and a vertical plane.
8 The control signals are difficult tQ produce because not only has the 9 antenna to be positioned to receive the signals radiated by a specified transmitter, but the antenna also has to be adjusted so as to guarantee reception 11 of the radiated transmitter power.
~2 It is thus an object of the present invention to provide an improved method 16 for receiving signals transmitted by a satellite transmitter, obviating the afore-17 stated drawbacks.

19 In particular, it is an object of the present invention to improve the method for receiving signals transmitted by a satellite transmitter so that the antenna 21 orientation with respect to the transmitter is automatically adjusted.

23 According to one aspect of the invention, the antenna is aligned with a b00 ' d dS0 ~ t0 00/Z0/ Z T EEZZtt~ZZ'LZ S-I1 N3S I 32j3I ~~ W /,?dN3H
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1 theoretical receive direction corresponding to a known location of the satellite.
2 The electromagnetic power received in the receive direction is compared with an 3 optimally possible satellite power known for the selected satellite. if the received 4 electromagnetic power is different from the optimally possible satellite power of the selected satellite, then the antenna is rotated in a direction where the G received power is greater.

8 With this method, it is possible to use the transmitter pf a specified satellite 9 to adjust the antenna to an optimal receive position. For this purpose, the known position of the satellite is first entered into a computer. The computation is based 11 n the respective terrestrial coordinates of the antenna location. The computer 12 uses these two data sets to calculate a direction in which theoretically an optimal 13 power reception from the satellite's transmitter can be expected. The antenna is ~? 4 then rotated in the horizontal and vertical direction according to this calculated direction Thereafter, the power reaching the antenna is compared with the 16 optimal power expected from the transmitter to determine if the antenna is 17 optimally oriented with respect to the transmitter. If the orientation is not yet 18 optimized, then the measure of the deviation from the optimal power is also a 19 measure in which direction and by how much the antenna has to be rotated until it is in a position where the expected received power is optimal.

22 According to a preferred embodiment of the invention, the theoretical 23 receive direction of the antenna is calculated from a known orbital position of the S00'd d90~b0 00/70/ZT EE~~bb~~Z~ S11 N3SI52~3I3~ W , ?dN3H
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1 selected satellite and the geographic coordinates of the terrestrial location. In 2 view of the substantially linear path of the electromagnetic beam radiated from 3 the transmitter, the antenna can be oriented so as to substantially meet the 4 optimal receiving conditions The antenna is aligned by checking if the received satellite power increases or decreases in an adjacent rotation position.

7 According to another preferred embodiment of the invention, an antenna 8 window is defined and a search for the satellite is performed in the window 9 opening. If the satellite is not found within the window opening, then a second window with an enlarged window opening is superimposed on the first window, 11 and the search is continued. It can then be determined by decreasing or 12 increasing the respective window size how a further search for the specified 13 transmitter is to be conducted.

According to another preferred embodiment of the invention, the identity of 16 a detected satellite is checked and the coordinates of the detected satellite are 17 compared with the coordinates of the selected satellite. Difference data are 18 determined from this comparison and the antenna is adjusted in response to 19 these difference data to paint in the direction of the selECted satellite.
In this way, also satellites that are not selected are included in the search pattern_ A
further 21 search for the desired satellite can then be based on the satellites that are not 22 selected and their position relative to the desired selected satellite.

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1 According to another preferred embodiment of the invention, the 2 difference data are determined as a deviation between the direction and an angle 3 of a detected satellite from the direction and angle of a selected satellite-These 4 two data sets, the direction and the angle between these directions, respectively, provide a measurement by which the antenna has to be aligned with respect to 6 the direction of the selected satellite-8 According to another preferred embodiment of the invention, a satellite 9 that has already been detected once, is not located a second time during a search for the selected satellite- Excluding an already tracked satellite during a 11 search a the desired satellite prevents the search for the desired satellite from 12 being restricted to the region where a certain satellite with a particularly high 13 radiated transmitter power has been found before. Without the exclusion of this 14 particular satellite, the selected satellite which may have a smaller radiated transmitter powEr may never be found in a furkher search or may be found only 16 with great difficulty.

18 According to another preferred embodiment of the invention, the direction 19 of an antenna is calibrated with reference to an already detected satellite whose direction has been recognized This measurement for the antenna can then be 21 used to adjust the antenna with respect to the selected satellite.

23 According to another preferred embodiment of the invention, the antenna

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1 can include a polarotor, wherein the polarization rotation can optimized via a 2 control line. The signal can be optimized by a suitable alignment of the polarotor 3 and adjustment of its rotation speed, with the signal being optimized based on 4 the received and radiated power of the antenna.

6 The antenna is preferably aligned with the help of a controller capable of

7 orienting the rotatable antenna towards an electromagnetic radiation source of a

8 satellite. Such controllers should be compact and easy to operate.

9 According to another aspect of the invention, the controller includes a first 11 input for inputting signals corresponding to a terrestrial location and a second 12 input for inputting signals corresponding to an actual orbital location of the 13 radiation source. The two inputs are connected with a comparator that compares 14 the respective signals with each other. The outputs of the controller are connected with drives for rotating the antenna. Such a controller can be 16 connected easily with input devices capable of providing, on one hand, 17 information about the respective terrestrial location and, on the other hand, 1 ~3 indicating the known orbital location of the selected satEllite. These two data 19 sets are then correlated in the controller by a computer, causing the output of the controller to transmit signals to the antenna drives. The signals controllably 21 move the antenna to a position where the power radiated by t>~e transmitter can 22 be received.

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1 According to another preferred embodiment of the invention, a housing 2 with those inputs can have an outside dimension corresponding tQ the outside 3 dimension of a housing in which customarily devices of radio navigation system 4 that control a ship's course are housed. The dimension of the housing enables the controller to conform to the housing dimensions customarily used onboard 6 ships, so that these two housing types can be easily intermingled. Since the 7 controller is preferably intended for used onboard ships, the controller will find 8 increased use because of its advantageous housing dimensions.

1o BRIEF DESCRIPTION GF THE DRAWING

1'o The above and other objects, features and advantages of the present 13 invention will be more readily apparent upon reading the following description of 14 a preferred exemplified embodiment of the invention with reference to the accompanying drawing, in which 17 FIG. 1 shows schematically a ship traveling within the range of two 18 satellites;

FIG. 2 shows schematically a rotatable antenna connected with a 21 controller; and 23 FIGS- 3 is a section through a controller along the line 111-III of FIG. 2.

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3 Throughout all the Figures, same or corresponding elements are generally 4 indicated by same reference numerals.
6 Turning now to the drawing, and in particular to FIG. 1, there is shown a 7 Referring first to FIG_ 1, a ship 1 is at sea 2 at a location 3 with assumed 8 coordinates X, Y. At this location 3, the ship travels within the range of twd 9 satellites 4, 5 which are equipped with transmitters 6, 7_ The transmitters 6, 7 radiate electromagnetic beams 8, 9 in the direction of the location 3. The 11 direction of the electromagnetic beams 8, 9 is determined, on one hand, by the 12 coordinates X, Y of the location 3 and, on the other hand, by the orbital '! 3 positions 10, 11 of the two satellites 4, 5. The electromagnetic beams 8, 14 radiated by the transmitters 6, 7 enclose an angle 12 according to the orbital positions 10, 11.

17 The electromagnetic beams 8, 9 are received by a rotatable antenna 13 18 installed on board the ship 1. The received beams 8, 9 provide exact data about 19 the ship's location 3. The transmitters 6, 7 can also transmit programs of interest onboard the ship 1, for example television programs, if the transmitters 6, 7 have 21 access to such television programs.

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1 by the electromagnetic beams 8, 9 can be lost, for example when changing 2 course or in heavy seas. There are other situations in which a connection 3 between the rotatable antenna 13 and the transmitters 6, 7 of the satellites 4, 5 4 has to be established- For this purpose, as seen more clearly in FIG 2, a controller 14 is provided onboard the ship 1 to establish a relationship between 6 the rotatable antenna 13 and the transmitter 6 of satellite 4_ For this purpose, a tiltable dish 15 is provided inside the rotatable antenna 13, with the dish being 8 rotatably supported for rotation about a horizontal axis 16 in a vertical plane and 9 about a vertical axis 17 in a horizontal plane 1$. An electric drive 19 is provided far rotating the dish 15 in the vertical plane and another electric drive 24 far 11 rotating the dish 15 in a horizontal plane.

13 ThE dish is connected by a connecting line 21 with an upper jack 22, the 14 drive 19 by a fine 23 with a center jack 24, and the drive 20 by a line 25 with a lower jack 26 of the controller 14. The jacks 22, 24, 26 are connected on top of 15 one another in a side wall 27 of the controller 14.

18 A computer 28 is located inside the controller 14_ The computer 28 is 19 connected to a satellite memory device 30 via a connecting line 29 and to a coordinate memory device 32 via a connecting line 31. Moreover, the two 21 memory devices 30, 32, the computer 28 and the jacks 22, 24, 26 are connected 22 to a current source 39, for example a rectifier The current source 39 also 23 supplies electric power to operating switches 40, 41, 42, 43 implemented, for ZTe~d d9Qi~t0 00/20/2L EEZZbbz~TZ X11 N3SI~2~3I3~ W 1~2~N3H
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1 example, as momentary contact switches_ The operating switches 40, 41, 42, 2 are arranged on a front panel 44 of the controller 14 The front panel 44 may also 3 incorporate a display 45 to indicate the respective operating state of the 4 controller 14_ 6 Two additional jacks 47, 48 which connect the controller 14 to a 7 compass 49 and a power source 15 for supplying power to the rectifier 39 are 8 arranged in a side wall located opposite the side wall 27. Also located on the 9 front panel 44 of the controller 14 are three LED's 51, 52, 53 which can emit light in different colors, such as red, yellow and green, to indicate the switching state 1 1 of the controller 14.

13 The rotatable antenna 13 can be aligned with a selected satellite 4 by first 14 inputting the orbital coordinates of satellite 4 from the satellite memory device 30 into the computer 28 via the connecting line 29. The terrestrial coordinates of the 16 location 3 are then determined by the compass 49 and inputted into the computer 17 28 via the jack 47. For these two values, the computer 28 then calculates the 18 ideal path of the electromagnetic beams 8 from the satellite's transmitter 6 to the 19 rotatable antenna 13. The computer 28 controls the electric drives 19, 20 according to the ideal path so as to align the rotatable dish 15 in the direction of 21 the transmitters 0 of the selected satellite 4. The memory device 30 not only 22 stores the orbital position of the satellite, but also the optimal power of the 23 beam 8 radiated by the transmitter 6. These values are also inputted in the Z20 " d d90 ~ t0 00/~0l Z 2 E6~Zb~ZZZZ S-1-1 N3S I 3L13I 3~ W .~2jN3H
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1 computer 28. After the dish 15 is oriented, the received electric power is also 2 inputted in the computer 28 for a comparison with this optimal power, The 3 computer 28 compares the optimal power of the transmitter 6 with the power 4 received by the dish 15. When the computer 28 detects the difference between the optimal power of the transmitter 6 and the received power of the dish 15, then 6 the computer 28 converts this difference into a switching signal which is used to 7 move the electric drive 19 or the electric drive 20 or both drives 19, 20.
These 8 drives rotate the dish 15 in accordance with the received control signal in a 9 direction for which of the computer 28 has computed an increase of the power received by the dish 15. If the program and the computer 28 operate correctly, 11 then the dish 15 rotates in a direction in which the power recEived by the dish 15 12 from the transmitters 6 increases. This rotation continues until the received 13 power corresponds to the programmed reduction of the transmitted power of 14 transmitter 6.
16 However, if after a rotation of the dish 15 the received power is less than 17 the theoretical power computed by the computer 28 for the position of the 8 dish 15, then the value of the power that was mast recently received by the 19 dish 15 is entered into the computer 28 and compared with the previously computed power received by the dish 15. If a difference is observed which would 21 necessitate a further rotation of the dish 15, then the computer 28 computes 22 which of the two drives 19, 20 has to be energized to rotate the dish 15 in a 23 direction where the dish 15 receives more electromagnetic power from the sz0-d d90:vm meize~izi ee.za~taziz s~~ N~sma3m~ w ~aN~H
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1 transmitter 6 than before. By properly comparing the power received by the dish 2 15 with the power transmitted by the transmitter 6, the antenna 13 is finally 3 placed in a position where an optimal portion of a power transmitted by the 4 transmitter 6 is received.
6 The operating switches 4~ can be used to select one of several 7 satellites 4, 5. The selected satellite 4 is then indicated on the display 45.

9 When the ship 1 changes course, the new course determined by the compass 49 is entered into the computer via the switch 41. The computer 28 11 then controls the dish 15 in accordance to the new course via the two drives 19, ~ 0 20. If the orientation of the dish has to be corrected manually independent of the 13 control exercised by the computer 28, then the dish 15 can be rotated vertically 14 by energizing the drive 19 via the operating switch 42. The dish 15 can be rotated horizontally relative to the satellite 4 by energizing the drive 2D
via the 16 operating switch 43.

18 The antenna 13 can also be aligned by tilting the antenna by an angle 12 19 from the direct line of sight with the satellite 5. In this case, the direction of the beam 9 can be entered into the computer 28 if this direction has not yet been 21 stored based on a previous tilting motion of the dish 15, The direction of the 22 beam 8 can tie inputted into the computer 28 by entering the angle 12, thereby 23 controlling the drives 19, 20 with respect to the desired position of the satellite 4.
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1 In a similar manner, when searching for a selected satellite 4, the antenna 13 can 2 be initially aimed at the satellite 5. In this case, it turns out to be faster to base a 3 change in the antenna direction on the location of the satellite 5 and to then aim 4 the antenna at the satellite 4 with a corrective motion, rather than starting a new search by using the known orbital cQOrdinates of the satellite 4.

7 In the event that the orbital position of the satellite 4, 5 has not yet been 8 established, the measured direction of the electromagnetic beams 9 and the 9 orbital position of the satellite 5 can also be used to calibrate the entire system.
1 Q Based on this calibration and the deviation of the orbital position of the selected 11 satellite 4 from the orbital position of the satellite 5, the antenna 13 can be 12 quickly adjusted with respect to the selected satellite 4.

14 The computer 28 is programmed so that the satellite 5 which is not selected, is targeted only once when searching for the selected satellite 4.
This 16 prevents multiple targeting of this satellite 5 which may still serve as a reference 17 satellite. This multiple targeting could pose a problem if the power of the 18 transmitter 7 is significantly greater than the power of transmitter 6 located in the 19 selected satellite 4. The search for the satellite 4 would become much more difficult in that the satellite 5 could be detected several times in a row, whereby 21 the orbital position of the selected satellite 4 would be computed based on the 22 position of satellite 5, without actually closing in on the satellite 4.

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1 As seen in FIG 1, a search region can be initially defined in which a 2 search for the satellite 4 is performed. This produces a window 54 with 3 boundaries within which the selected satellite 4 should be found. However, if the 4 satellite 4 cannot be fiound inside this window 54, then the size of the window 54 is systematically increased by adding extensions 55 until the selected satellite 4 6 falls inside the window 54, 55 8 Moreover, the efficiency of the antenna 13 may be further enhanced by 9 controlling a polarotor 56 located in front of the dish 15 in the direction of the beams 8. The polarotor 56 is driven by a drive 57 and rotates in front of the 11 dish 15. The poiarotor 56 can be tilted relative to the beams 8 depending on the 12 characteristic properties of the incoming electromagnetic beams 8.

14 The effect from the polarotor 5f can be enhanced by adjusting its rotation speed and tilt relative to the beams 8. For example, when the computer 28 16 detects a difference between the power radiated by the transmitter 6 and the 17 power received by the dish 15, the rotation speed andJor tilt of the polarotor 56 18 can be adjusted to make the antenna 13 more efFective While the invention has been illustrated and described as embodied in a 21 method for homing in on a selected satellite and a controller for orienting a 22 rotatable antenna, it is not intended to be limited to the details shown since 23 various modifications and structural changes may be made without departing in 9Z0'd d90~b0 00/70/LT EE~Ztb~ZZZ S11 N3SI3~13I3~ W .~2jN3H
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1 any way from the spirit of the present invention.
3 What is claimed as new and desired to be protected by Letters Patent is 4 set forth in the appendEd claims;
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Claims (21)

What is claimed is:

1. A method for homing in on a selected satellite from a predetermined terrestrial location whose geographic coordinates are known, comprising the steps of:
- controlling an antenna that is rotatably supported for rotation in respective horizontal and vertical planes, to a theoretical receive direction corresponding to a known location of the selected satellite, - comparing an electromagnetic power received from the selected satellite in the theoretical receive direction with an optimally possible satellite power known for the selected satellite; and - in the event that the received electromagnetic power from the selected satellite is different from the optimally possible satellite power known for the selected satellite, rotating the antenna in a receive direction having an increased electromagnetic power.

2. The method of claim 1, wherein the theoretical receive direction of the antenna is calculated from a known orbital position of the selected satellite and parameters representing the geographic coordination of the terrestrial location.

3. The method of claim 1, and further comprising the steps of defining for the antenna a first window having a first window opening; searching the position of the satellite in the window opening; if the search within the window opening is without a result, superimposing a second window on the first window, the second window having an enlarged window opening as compared to the first window; and repeating searching and enlarging a respective window opening until the selected satellite is located.

4. The method of claim 1, and further comprising the steps of checking an identity of a detected satellite; comparing the coordinates of the detected satellite with coordinates of the selected satellite; determining difference data based on the comparison; and controllably adjusting the antenna in response to the difference data in a direction towards the selected satellite.

5. The method of claim 4, wherein the difference data comprise respective directions and an angle between the directions of a detected satellite and the selected satellite.

6 The method of claim 1, wherein when searching for the selected satellite, an already detected satellite is no longer located.

7. The method of claim 1, an orientation of the antenna is calibrated with reference to an already detected satellite whose receive direction has been recognized.

8. The method of claim 1, wherein a receive signal strength of the antenna is optimized by controlling a polarotor via a control line.

9. The method of claim 8, wherein the polarotor receives from the control line a control signal.

10. The method of claim 9, wherein the control signal is used to optimize a tilt of the polarotor.

11. The method of claim 9, wherein the control signal is used to optimize a rotation speed. of the polarotor.

12. A controller for aiming a rotatable antenna towards an electromagnetic radiation source of a satellite, comprising:
- a first input for inputting first signals corresponding to a terrestrial location of the antenna;
- a second input for inputting second signals corresponding to an actual orbital location of the radiation source; and - at least one output connected with a respective drive for rotating the antenna, - wherein the first input and the second input are connected with a comparison device that compares the respective first and second signals with each other.

13. The controller of claim 12, and further comprising a housing for supporting the first and second inputs, the housing having dimensions corresponding to dimensions of housings that customarily house devices that control a ship's course with the help of a radio navigation system.

14. The controller of claim 12, and further comprising a first storage device for storing satellite data, and a second storage device for storing terrestrial coordinates, wherein the comparison device is implemented as a computer connected with the first and second storage device.

19 95. The controller of claim 12, and further comprising a display that displays an operational state of the controller.

16. The controller of claim 15, wherein the display displays a satellite towards which the antenna is oriented.

17. The controller of claim 13, and further comprising operating switches disposed on a front panel of the housing for a manually controlling the controller.

18. The controller of claim 17, wherein one of the operating switches is adapted to switch to the selected satellite.

19. The controller of claim 17, wherein one of the operating switches is adapted to correct the terrestrial location.

20. The controller of claim 17, wherein one of the operating switches is adapted to control the antenna.

21. The controller of claim 13, and further comprising a plurality of displays disposed on a front panel of the housing to indicate an actual operational state of the controller.