US3772701A - Satellite antenna autotrack system permitting error signals to appear at the earth station - Google Patents

Satellite antenna autotrack system permitting error signals to appear at the earth station Download PDF

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Publication number
US3772701A
US3772701A US00114451A US3772701DA US3772701A US 3772701 A US3772701 A US 3772701A US 00114451 A US00114451 A US 00114451A US 3772701D A US3772701D A US 3772701DA US 3772701 A US3772701 A US 3772701A
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beams
antenna
pair
generating
signals
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E Wilkinson
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Comsat Corp
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Comsat Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
    • G01S3/02—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using radio waves
    • G01S3/14—Systems for determining direction or deviation from predetermined direction
    • G01S3/146—Systems for determining direction or deviation from predetermined direction by comparing linear polarisation components

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  • ABSTRACT Primary Examiner-Benjamin A. Borchelt Assistant Examiner-Richard E. Berger [57] ABSTRACT
  • the invention pertains to satellite antenna autotrack systems which permit error signals to appear at the ground station rather than at the satellite's antenna.
  • a conventional four horn cluster is used to produce pairs of circularly polarized position signals which are detected and processed at the ground station to produce vertical and horizontal error signals.
  • the four horn cluster is simultaneously used to transmit the satellite's down link communications signals.
  • the error signals are transmitted from the ground station to the satellite to reposition the satellites vertical and horizontal axis to correspond to the line of sight to the groun d station.
  • a prior system for accomplishing line of sight correspondence includes equipment for generating the error signals at the terminals of the satellites antenna. Such a system necessitates the placing of the autotrack receiving and signal processing equipment, which often requires maintenance, on the satellite itself. Thus, maintenance of the receiving and processing equipment becomes most difficult and often impossible.
  • the instant invention provides a satellite antenna autotrack system which permits error signals to be generated at the ground station rather than at the satellites antenna terminals thereby reducing the equipment on board the satellite.
  • a pair of horns are displaced equally on opposite sides of the focal axis of a parabolic reflector.
  • a second pair of horns are similarly arranged, but in a plane 90 from the first pair.
  • Each pair provides signals to the ground station which enables the ground station to determine the offset of the satellite antenna pointing direction in the plane containing that pair of horns. Error signals are generated, correspondingto the offsets and are transmitted to the satellite to control the antenna servo motors to point the antenna in a direction to reduce the errors to zero.
  • the first and second pair of horns will be referred to herein as producing horizontal and vertical position signals.
  • All four horns are excited by the same communications signal to provide a down link antenna lobe pattern whose axis is the pointing direction of the antenna.
  • Beacon frequencies are applied to the horns in such a manner that opposite sense circularly polarized signals are radiated by opposite horns with the corre sponding beams being squinted away from the focal axis in opposite directions.
  • the down link communications signal is at a third frequency and is radiated with identical polarization from all four horns.
  • satellite antenna pointing direction (focal axis) is coincident with the radio line of sight between the satellite and the ground station, equal intensity left and right circularly polarized signals are received at the ground station for each of the two beacon frequencies.
  • the signal radiating from one horn of each corresponding pair of horns will appear at the earth station with greater intensity than the signal from the opposite horn.
  • the ground station which includes a single horn antenna with dual circularly polarized outputs of opposite sense receives the position signals and the downlink communications signals. Suitable processing equipment generates vertical and horizontal error signals in response to the receivedposition signals.
  • FIG. 1 illustrates the satellite antenna feed excitation system of this invention for producing vertical and horizontal position signals
  • FIG. 2 illustrates the ground antenna feed excitation system of this invention for producing vertical and horizontal error signals proportional 'to the received intensity of the position signals
  • FIG. 3 represents one example of a command system adapted to transmit the error signals to the satellite, receive the signals at the satellite and correct the satellite antenna position, and
  • FIG. 4 illustrates in simplified form how the pointing axis offset is seen at the ground station.
  • FIG. 1 shows the satellite antenna feed excitation systern for use with this invention.
  • the four horn cluster 2 comprises horns A, B, C and D. Each horn is excited with a pair of orthogonal, linearly polarized probes. Theseprobes are designated A A B B C C D H and Dy for horns A, B, C and D respectively.
  • the four horns are located in the focal plane of a large parabolic reflector on board the satellite.
  • Terminals A A B By, C Cy, D and D, are each connected to their correspondingly designated probes.
  • Horns A and C may be viewed as operating in conjunction to develop vertical position signals with horns B and D operating in conjunction to develop horizontal position signals.
  • a vertical beacon frequency f is applied to the linear probes of the horns A and C in a manner to result in an f, beacon of right hand circular polarization radiated from horn A and an f beacon of left hand circular polarization radiated from horn C.
  • the horizontally positioned probes, A and C receive the beacon frequency signal f directly while the vertically aligned probes A and Cy receive the beacon frequency signal f, in phase
  • the beacon frequency signal f is applied through a delay line, 4, which may be any conventional device resulting in a phase shift of the input signal to delay line 4.
  • the output of delay line 4 is applied to the difference terminal, A, of a conventional hybrid circuit 6 resulting in output signals at terminals A and Cy of equal amplitude and frequency, but of opposite phase.
  • the f signal at A will have the same phase as the input to the terminal A, whereas the f, signal at Cy will be 180 out of phase with the input to terminal A. Both of the latter mentioned f signals will be 90 out of phase, or in phase quadrature, with the corresponding f signals applied to probes A and C Since the signals at frequency f, which are applied to horn A are in space quadrature (two electric field vectors oriented 90 apart in space) and phase quadrature, the resulting f beacon radiated by horn A will be circularly polarized. The same is true for the f, beacon radiated by horn C. However, since in one horn the f signal applied to the horizontal probe phase leads the f signal applied to the vertical probe, and in the other horn the opposite is true, the two circularly polarized beacons will be of opposite sense.
  • the four horn cluster 2 radiates the down link communications signal from the satellite to the ground station. This is accomplished by applying the down link communications signal through the summation terminals 2 of hybrids 6 and 10 respectively to probes A By, Cy and D only.
  • the down link communications signal is vertically polarized. It will be noted that the signal applied to the summation terminal 2 of either hybrid 6 or 10 results in equal amplitude, equal phase signals at the input frequency.
  • FIGS. 4A and 4B a simplified pictorial representation of a two dimensional system will now be presented in connection with FIGS. 4A and 4B.
  • the numeral 43 designates the ground station antenna and it is assumed that it is pointing at the satellite.
  • Ground station autotrack systems are well known for accomplishing the latter function.
  • the satellite antenna isdesignated by the numeral 41 and as shown in FIG. 4A the satellite antenna pointing direction 51 is substantially coincident with the line of sight path 49.
  • the lobe patterns 45 and 47 represent two radiation beams in the same plane, e.g., vertical, and as explained above are radiated by the horns, such as horns A and C in FIG. 1, on opposite sides of the antenna pointing direction.
  • the two beams are distin guishable since they are circularly polarized in opposite sense.
  • the ground station will detect substantially the same amount of energy from both radiation beams indicating that the satellite antenna is properly pointing in the vertical plane.
  • FIG. 48 indicates the case of the satellite pointing axis 51 being angularly offset in the vertical plane from the line of sight path 49. This condition will be detected junction 18.
  • the difference terminal A of hybrid 18 is coupled to diplexer 20 while the summation terminal 2 I is coupled to diplexer 22 through coupler 19.
  • the sumat the ground station by receiving a greater amount of radiation from the lobe 47 than from the lobe 45.
  • the ground station then generates a vertical error signal which is transmitted to the satellite to cause angular movement of the satellite antenna to bring'the pointing axis 51 in line with the line of sight 49 as in FIG. 4A.
  • ground station detects the differing amounts of radiation received from the two radiation lobes in each of the coordinate planes and demation terminal 2 output signal is also coupled through coupler 19. to the ground station's communications equipment (not shown).
  • One output of diplexer 20 is coupled to one input of a two channel tracking receiver 24 with the second output of the diplexer 20 being coupled to one input of two channel tracking receiver 26.
  • one output from diplexer 22 is coupled to a second input of the two channel tracking receiver 24 with the second output of diplexer 22 being coupled to the other input of two channel tracking receiver 26.
  • the signal at the output of tracking receiver 24 will be the horizontal error signal while the signal at the output of receiver 26 will be the vertical error signal. It is, understood by those skilled in the art that the vertical error signal may be generated at the output of receiver 24 while the horizontal error signal may be generated at the output of receiver 26 merely by rearranging the inputs to the receivers from the diplexers 20 and 22.
  • the single horn 14 with phase shifter 16 may be best understood by describing the device as a transmitter and remembering that it will have reciprocal operation as a receiver.
  • a signal applied to E will be vertically polarized.
  • the phase shifter 16, positioned at 45 to the plane of polarization will split the signal into its space quadrature components with one component lagging the other in phase by The result is a left hand circularly polarized signal.
  • Diplexer 20 which is coupled to the A terminal of hybrid 18, separates the difference signals, with the signal corresponding to the vertical misalignment, that is, the signal at frequency f being fed to tracking receiver 26 while the signal corresponding to the horizontal misalignment of the antenna being applied to the tracking receiver 24.
  • the summation terminal 2 or hybrid 18 appears the sum of the circularly polarized signals for each of the beacon frequencies as well as the down link communications signal.
  • the sum signal is applied through coupler 19 to the ground stations communication equipment (not shown) and diplexer 22.
  • the sum signal is separated into signals at frequencies f and f, to provide reference signals to receivers 24 and 26.
  • Tracking receivers 24 and 26 are known in the art.
  • One example of a receiver which can be used as receivers 24 and 26 is the ITT Model 4004 Pulse Tracking Receiver manufactured by lnternational Telephone and Brass Corporation. In a manner known in the art the tracking receivers process the inputs thereto and produce error signals proportional to the antennas misalignment.
  • error signals are coupled to the ground station's command system which modulates and transmits them to the satellite via the ground to satellite communications link.
  • the error signals are detected and separated from the communications and command signals and used to drive suitable antenna position correcting apparatus.
  • Ground station and satellite command systems as well as antenna position cor-. recting apparatus as known in the art and a description thereof is not necessary for a full understanding of this invention.
  • a brief description of a known command system will be given to illus- .trate how the error signals can be transmitted from the ground station to the satellite.
  • FIG. 3 there is illustrated one command system which utilizes audio tones sent out in bursts, the number of bursts being sent representing the command.
  • These command tones are sent to the satellite via a frequency modulating system.
  • Each of the error signals is applied to a frequency deviator simultaneously with the command tones and command carrier signals.
  • the horizontal error signals may be applied to one input of frequency deviator 30 with the vertical error signals being applied to one input of frequency deviator 32.
  • a command carrier signal to the frequency deviators 30, 32, the carrier is frequency modulated in response to the error voltages.
  • the modulated command signals are then combined with the ground to satellite communications signals in directional filter 34.
  • the composite signal is transmitted to the satellite by means of the ground station transmitting antenna 36.
  • the error signals being at a much lower frequency than the audio command tones, can be easily separated from the audio command tones by a simple low pass filter after detection in the satellite.
  • the composite ground to satellite signal is received at the satellite 's receiving antenna 38.
  • the ground antenna has a separate conventional autotrack system of its own (not shown) operating to keep the ground antenna pointed at the satellite.
  • the signal received at the satellite's antenna 38 passes through a repeater 40 which reduces the center frequency of the carrier signals.
  • the transmitted carrier may have a center frequency at 6GHZ; with the output signal of the repeater having a center frequency at 4GHZ.
  • the modulated composite signal passes through directional filter 42 wherein the communications signal is separated from the command signal.
  • the communications signal is processed by communications signal processing equipment on board the satellite (not shown). Such equipment and its operation is not part of the invention and a description thereof is not necessary for a full understanding thereof.
  • the modulated command carrier is passed through a conventional mixer amplifier 44 to discriminators 46 and 48.
  • the discriminators remove the command carriers to produce the command tones and the horizontal and vertical error signals. Since the frequency of the error signals is much lower than the frequency of the tone signals, low pass filters 50 and 52 effectively separate the vertical and horizontal error signals from the tone signals. These error signals are applied to suitable servo systems to drive the satellite antenna into alignment.
  • an antenna autotrack system for aligning a transmitter antenna pointing direction to correspond to the line of sight between a receiver antenna of a receiver and said transmitter antenna, the receiver producing error signals proportional to the angular offset of the transmitter antenna pointing direction with respect to the receiver, the improvement comprising:
  • a. means at said transmitter for generating electromagnetic beams said means including first radiator means, displaced in a first plane on opposite sides ofthe focal axis of said transmitter antenna for generating a first pair of distinguishable, directional electromagnetic beams and second radiator means, displaced in a second plane on opposite sides of said focal axis for generating a second pair of distinguishable, directional electromagnetic beams, said second pair of beams being distinguishable from each other and from said first pair of beams; and
  • b. means, at said receiver, for receiving said beams and generating error signals proportional to the difference in the received intensities of said first pair of beams and said second pair of beams.
  • said means for receiving and generating includes means for distinguishing between said first and second pairs of beams and for generating error signals corresponding 7 to said angular offset of the pointing direction in said first and second planes, said error signals being proportional to the difference in the intensities of said received beams which comprise a pair of beams.
  • beacon means for generating beacon signals of different frequencies
  • a first pair of radiators each radiator including a pair of orthogonal, linearly polarized probes responsive to beacon signals of a first frequency, for generating a first pair of circularly polarized beams of opposite sense
  • a second pair of radiators each radiator including a pair of orthogonal, linearly polarized probes responsive to beacon signals of a second frequency, for radiating circularly polarized beams of opposite sense.
  • a ground station for producing error signals proportional to the offset of the antenna pointing direction with respect to the ground station comprising:
  • b. means, responsive to the difference in the intensity of said received beams, for generating error signals proportional to the difference in the intensities of said received beams.
  • a transmitting system including a transmitting antenna for generating electromagnetic beams to enable a distant ground receiving station to determine the offset of the pointing direction of the transmitting system antenna from the line of sight between the transmitting system and the ground receiving means comprising:
  • beacon means for generating beacon signals of different frequencies
  • each radiator including a pair of orthogonal, linearly polarized probes responsive to a beacon signal of a first frequency, for generating a first pair of circularly polarized beams of opposite sense;
  • each radiator including a pair of orthogonal, linearly polarized probes responsive to a beacon signal of a second frequency for generating a second pair of circularly polarized beams of opposite sense.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)
  • Radio Relay Systems (AREA)
US00114451A 1971-02-11 1971-02-11 Satellite antenna autotrack system permitting error signals to appear at the earth station Expired - Lifetime US3772701A (en)

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US11445171A 1971-02-11 1971-02-11

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AU (1) AU457885B2 (enExample)
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Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3997901A (en) * 1970-06-23 1976-12-14 U.S. Philips Corporation Method of directing an aerial to a receiver according to a main direction
US4213130A (en) * 1977-11-07 1980-07-15 Hollandse Signaalapparaten B.V. Monopulse radar apparatus
US4599619A (en) * 1982-07-13 1986-07-08 Rca Corporation Satellite dual antenna pointing system
US4630058A (en) * 1982-02-26 1986-12-16 Rca Corporation Satellite communication system
US4785302A (en) * 1985-10-30 1988-11-15 Capetronic (Bsr) Ltd. Automatic polarization control system for TVRO receivers
US4801940A (en) * 1985-10-30 1989-01-31 Capetronic (Bsr) Ltd. Satellite seeking system for earth-station antennas for TVRO systems
US5187805A (en) * 1989-10-02 1993-02-16 Motorola, Inc. Telemetry, tracking and control for satellite cellular communication systems
US5296861A (en) * 1992-11-13 1994-03-22 Trimble Navigation Limited Method and apparatus for maximum likelihood estimation direct integer search in differential carrier phase attitude determination systems
US5347286A (en) * 1992-02-13 1994-09-13 Trimble Navigation Limited Automatic antenna pointing system based on global positioning system (GPS) attitude information
EP0863407A1 (fr) * 1997-03-04 1998-09-09 Alcatel Antenne pour l'émission et/ou la réception de signaux à polarisation rectiligne
US6337658B1 (en) * 1999-11-30 2002-01-08 Nortel Networks Limited Transmit antenna alignment peak search method and apparatus
US6417803B1 (en) * 2001-04-03 2002-07-09 The Boeing Company Beam alignment system and method for an antenna
WO2003094287A1 (en) * 2002-04-30 2003-11-13 The Boeing Company Beam alignment methods for an antenna
US9608716B1 (en) 2016-04-06 2017-03-28 Space Systems/Loral, Llc Satellite transmit antenna ground-based pointing
US9678213B2 (en) 2013-01-31 2017-06-13 Eutelsat S A Data collection device and method for the localisation of a source of interference
US9853356B2 (en) * 2013-09-26 2017-12-26 Orbital Sciences Corporation Ground-based satellite antenna pointing system

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3534364A (en) * 1966-09-12 1970-10-13 Bell Telephone Labor Inc Attitude sensing system
US3560977A (en) * 1968-04-09 1971-02-02 Philips Corp Aerial follower device

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3534364A (en) * 1966-09-12 1970-10-13 Bell Telephone Labor Inc Attitude sensing system
US3560977A (en) * 1968-04-09 1971-02-02 Philips Corp Aerial follower device

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3997901A (en) * 1970-06-23 1976-12-14 U.S. Philips Corporation Method of directing an aerial to a receiver according to a main direction
US4213130A (en) * 1977-11-07 1980-07-15 Hollandse Signaalapparaten B.V. Monopulse radar apparatus
US4630058A (en) * 1982-02-26 1986-12-16 Rca Corporation Satellite communication system
US4599619A (en) * 1982-07-13 1986-07-08 Rca Corporation Satellite dual antenna pointing system
US4785302A (en) * 1985-10-30 1988-11-15 Capetronic (Bsr) Ltd. Automatic polarization control system for TVRO receivers
US4801940A (en) * 1985-10-30 1989-01-31 Capetronic (Bsr) Ltd. Satellite seeking system for earth-station antennas for TVRO systems
US5187805A (en) * 1989-10-02 1993-02-16 Motorola, Inc. Telemetry, tracking and control for satellite cellular communication systems
RU2134488C1 (ru) * 1989-10-02 1999-08-10 Моторола, Инк. Система управления для спутниковой системы связи и телеметрическая следящая и управляющая система связи
US5347286A (en) * 1992-02-13 1994-09-13 Trimble Navigation Limited Automatic antenna pointing system based on global positioning system (GPS) attitude information
US5296861A (en) * 1992-11-13 1994-03-22 Trimble Navigation Limited Method and apparatus for maximum likelihood estimation direct integer search in differential carrier phase attitude determination systems
WO1998039666A1 (fr) * 1997-03-04 1998-09-11 Alcatel Antenne pour l'emission et/ou la reception de signaux a polarisation rectiligne
FR2760569A1 (fr) * 1997-03-04 1998-09-11 Alsthom Cge Alcatel Antenne pour l'emission et/ou la reception de signaux a polarisation rectiligne
EP0863407A1 (fr) * 1997-03-04 1998-09-09 Alcatel Antenne pour l'émission et/ou la réception de signaux à polarisation rectiligne
US6300900B1 (en) 1997-03-04 2001-10-09 Alcatel Antenna for transmitting and/or receiving signals with rectilinear polarization
US6337658B1 (en) * 1999-11-30 2002-01-08 Nortel Networks Limited Transmit antenna alignment peak search method and apparatus
US6417803B1 (en) * 2001-04-03 2002-07-09 The Boeing Company Beam alignment system and method for an antenna
WO2003094287A1 (en) * 2002-04-30 2003-11-13 The Boeing Company Beam alignment methods for an antenna
US9678213B2 (en) 2013-01-31 2017-06-13 Eutelsat S A Data collection device and method for the localisation of a source of interference
US9853356B2 (en) * 2013-09-26 2017-12-26 Orbital Sciences Corporation Ground-based satellite antenna pointing system
US10770788B2 (en) 2013-09-26 2020-09-08 Northrop Grumman Innovation Systems, Inc. Ground-based satellite antenna pointing system
US9608716B1 (en) 2016-04-06 2017-03-28 Space Systems/Loral, Llc Satellite transmit antenna ground-based pointing

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Publication number Publication date
GB1352085A (en) 1974-05-15
CA998458A (en) 1976-10-12
AU3879072A (en) 1973-08-16
IT949052B (it) 1973-06-11
FR2125394B1 (enExample) 1977-03-18
AU457885B2 (en) 1975-02-13
FR2125394A1 (enExample) 1972-09-29

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