EP0152221A2 - Station terrienne pour systèmes de télécommunications par satellite - Google Patents

Station terrienne pour systèmes de télécommunications par satellite Download PDF

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Publication number
EP0152221A2
EP0152221A2 EP85300563A EP85300563A EP0152221A2 EP 0152221 A2 EP0152221 A2 EP 0152221A2 EP 85300563 A EP85300563 A EP 85300563A EP 85300563 A EP85300563 A EP 85300563A EP 0152221 A2 EP0152221 A2 EP 0152221A2
Authority
EP
European Patent Office
Prior art keywords
reflector
sub
feed
satellite
antenna
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP85300563A
Other languages
German (de)
English (en)
Other versions
EP0152221A3 (fr
Inventor
David Garrood
Roger Crawshaw
Robert Ian Henderson
Frank Allwood Dutton
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Co PLC
Original Assignee
General Electric Co PLC
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
Priority claimed from GB848428155A external-priority patent/GB8428155D0/en
Priority claimed from GB858501944A external-priority patent/GB8501944D0/en
Application filed by General Electric Co PLC filed Critical General Electric Co PLC
Publication of EP0152221A2 publication Critical patent/EP0152221A2/fr
Publication of EP0152221A3 publication Critical patent/EP0152221A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
    • H01Q19/12—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces wherein the surfaces are concave
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/27—Adaptation for use in or on movable bodies
    • H01Q1/32—Adaptation for use in or on road or rail vehicles
    • H01Q1/3208—Adaptation for use in or on road or rail vehicles characterised by the application wherein the antenna is used
    • H01Q1/3216—Adaptation for use in or on road or rail vehicles characterised by the application wherein the antenna is used where the road or rail vehicle is only used as transportation means

Definitions

  • This invention relates to an earth terminal for satellite communication systems.
  • the invention arose in the design of a road transportable terminal.
  • a previous design had incorporated a circular antenna reflector of three metres diameter which, whilst large for the purposes of road transport, presented no insurmountable problems in this respect.
  • This invention provides an earth terminal for a satellite communication system comprising an antenna system designed and arranged so that the main lobe of it's gain characteristics is broader in a direction perpendicular to the orbit of the satellite than in the direction of the orbit of the satellite. For this reason the idea of having one dimension of the reflector (the horizontal dimension) greater than the other was proposed. Surprisingly it was found that the limitation on the second dimension does not present a problem. This is because many communication satellites are arranged in geostationary orbits which all lie on a common equatorial great circle and will thus be seen to lie in a continuous line when viewed from any part of the earth's surface, this line extending for practical purposes in the azimuth direction. Lack of directionality in a direction perpendicular to this line (i.e., in elevation) and due to the relatively small "second" dimension of the antenna reflector therefore does not cause interference with neighbouring satellites.
  • the invention provides an earth terminal for a satellite communication system comprising an antenna system designed and arranged so that the main lobe of it ' s gain characteristics is broader in a direction perpendicular to the orbit of the satellite than in the direction of the orbit of the satellite.
  • an earth terminal in accordance with the invention, preferably includes means for tracking the satellite in the direction of the orbit: which will normally call for adjustment of the antenna in azimuth. This is desirable because the highly directional characteristics of the antenna in the direction of the geostationary orbit mean that the beamwidth does not simultaneously illuminate the whole of the area of movement of the satellite.
  • the azimuth tracking facility also greatly facilitates setting up of the system when it arrives at it ' s destination since it eliminates the need to set the azimuth of the boresight of the antenna accurately to the known centre of movement of the satellite.
  • This has previously been a problem in transportable satellite communication systems because of the difficulty in obtaining an accurate azimuth reference. It would also be a problem in domestic, community and like terminals designed just to receive and not to transmit where speed and ease of installation is important for cost reasons.
  • the invention whilst particularly applicable to transportable systems can thus be usefully applied to some fixed systems. Also, it is apparent from the foregoing that, whilst the invention is particularly applicable to the type of antenna which incorporates a reflector dish, the invention would also be applicable to phased array antennas.
  • the earth terminal of this invention preferably does not include means for tracking the satellite in a direction perpendicular to the orbit, which will normally be in elevation.
  • the cost of including an elevation tracking system is not considered necessary firstly because the relatively short "second" dimension of the reflector can give a beamwidth in elevation sufficiently wide to embrace the whole area of movement of the satellite; and secondly because accurate inclination measuring devices are available. This means that the previously mentioned difficulty of correctly setting the azimuth of the antenna does not apply to setting the elevation.
  • the sub-reflector and preferably also the feed are mounted on a pivotted supporting frame which can be folded away to a position close to the main reflector. This makes a compact arrangement either for transportation by road if the whole assembly is formed as part of a road trailer or vehicle, or for storage in a standard container, or for fitting into an aircraft fuselage.
  • a transportable antenna comprising a supporting structure, a main antenna pivotted relative to the supporting structure about orthogonal axes, a sub-reflector, a feed, and a supporting frame carrying the sub-reflector and pivotted relative to the reflector so as to enable the sub-reflector to be pivotted from an operational position where it is spaced from the main reflector to a position for transportation where it is located relatively close to the main reflector.
  • Another aspect of the invention aims to meet this requirement and provides a dual-reflector antenna comprising a feed, a sub-reflector arranged to be illuminated by the feed and a main reflector arranged to receive the radiation after reflection from the sub-reflector, characterised by a shielding device defining an annular region of shielding between the feed and the sub-reflector so as to obstruct radiation from the feed which would otherwise miss the sub-reflector.
  • This technique is applicable to any dual-reflector antenna (i.e., Cassegrain or Gregorian) whether or not forming part of a satellite communications sytem.
  • the technique can achieve a substantial reduction in "spillover” i.e., radiation missing the sub-reflector, thereby reducing the amount of radiation emitted in directions other than that required.
  • the shield also preferably has the effect of reducing the intensity of radiation in the edge regions of the main reflector thus reducing the amount of radiation which misses the latter.
  • FIG. 1 of the drawings there is illustrated a road-trailer-mounted offset Gregorian antenna with an elliptical main reflector 1 having a-first maximum dimension d l in the horizontal plane and a second minimum dimension d 2 in an orthogonal plane.
  • the reflector 1 has lugs one of which is shown at 2 by which it is pivotted about a horizontal axis on a turntable 3 which can be rotated about an orthogonal vertical axis on a frame 4 which forms part of a road trailer.
  • the trailer carries a television transceiver 5 from which energy to be transmitted is fed along a flexible waveguide 6 to a feed horn 8.
  • the feed horn 8, shielding device 9 and sub-reflector 10 are mounted on a framework 11 which is pivotted, about a horizontal axis, on lugs 12 fixed to the reflector 1.
  • the framework is held at the illustrated position by removable stays 13 each secured at one end to framework 11 and at the other end to a lug 14 also fixed to the reflector.
  • the feed horn 8, shielding device 9 and sub-reflector 10 are designed so as to illuminate substantially the whole of the main reflector 1.
  • the larger diameter d l results in a narrower beamwidth in azimuth than is achieved in elevation by the smaller diameter d 2 .
  • the sub-reflector 10 is designed to spread the energy arriving from the horn 8 across the axes d l and d 2 of the reflector 1 in such a way that the energy is- tapered from the centre of the reflector to the edges to a greater extent in the dimension d 1 than in the dimension d 2 . It is desirable to accomplish this because the greater taper in direction d 1 will result in a relatively lower level of sidelobes, while the lesser taper in d 2 , whilst resulting in higher sidelobes, assists in maintaining the highest possible directionality from the complete aperture.
  • the purpose of the shielding device 9, supported between the horn 8 and reflector 10 on struts 11A forming part of the framework 11, is to act as an obstruction to radiation from the horn which would otherwise miss the sub-reflector 10. It also reduces the radiation intensity at the edges of the sub-reflector and therefore in the region of the edges of the main reflector, thus reducing the amount of radiation from the sub-reflector which misses the main reflector.
  • the radiation which misses the two reflectors is called "spill-over" and it is desirable to reduce this as much as possible to minimise interference e.g., with other satellite communication systems.
  • the shielding device 9 is, as shown on Figure 1 formed by a frusto-conical metal surface tapering towards the sub-reflector. This is preferable to an annular surface since it enables a shielding effect to be obtained over a considerable angle without obstructing radiation passing from the sub-reflector to the main reflector.
  • the main lobe of the transmitted beam is shown schematically by the shaded area 15 on Figure 2. It's boresight 16 is shown aligned with a satellite 17 which moves within a roughly square region 18 centred on a geostationary orbit 19 of the satellite 17.
  • the reflector 1 lies substantially horizontally on the frame 4, the stays 13 are stowed away, and the framework 11 is folded so as to lie against the reflector.
  • An extension 11 B of the framework 11 extends through a hole 1A of the reflector 1 and is secured thereto by a catch mechanism (not shown) behind the reflector.
  • the reflector 1 When the illustrated transmitter is to be deployed the reflector 1 is tilted in elevation on its lugs 2 by manually operated jacks shown schematically at 20 and is rotated in azimuth using the turntable 3 and a servo mechanism 3A which engages teeth on the edge of the turntable.
  • An accurate inclination sensing instrument 1B is used to enable the boresight 16 to be set at the elevation of the satellite which will usually be as illustrated at approximately the highest point of the orbit 19.
  • the azimuth is then set roughly to the direction of the satellite using a relatively inaccurate compass.
  • Fine adjustment is then effected by an operator until the satellite has been acquired. Following this the satellite is automatically tracked in azimuth during movements from one side to another of the square 18.
  • the tracking is effected by automatic rotation of turntable 3 by the servo mechanism 3A under the control of the tranceiver 5 via line 5A.
  • the antenna will be needed in circumstances when the geostationary orbit 19 makes an angle of no more than 45° with the horizontal in the region 7. In such circumstances little penalty is paid in using an antenna with its major axis pemanently horizontal as in the illustrated example. There may however be circumstances where it is desired to communicate with a satellite in a part of the orbit which appears inclined to the horizontal. In such circumstances the antenna can take advantage of the features already described if the axis d l is inclined so that it lies effectively tangential to the position of the satellite in the geostationary arc as viewed from the antenna. Such an inclined mounting arrangement can be achieved on a mobile installation: but is more readily achieved on a permanent stationary installation.

Landscapes

  • Aerials With Secondary Devices (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)
  • Radio Relay Systems (AREA)
EP85300563A 1984-02-09 1985-01-28 Station terrienne pour systèmes de télécommunications par satellite Withdrawn EP0152221A3 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
GB8403445 1984-02-09
GB8403445 1984-02-09
GB8428155 1984-11-07
GB848428155A GB8428155D0 (en) 1984-02-09 1984-11-07 Earth terminal
GB8501944 1985-01-25
GB858501944A GB8501944D0 (en) 1984-11-07 1985-01-25 Transportable antenna

Publications (2)

Publication Number Publication Date
EP0152221A2 true EP0152221A2 (fr) 1985-08-21
EP0152221A3 EP0152221A3 (fr) 1986-11-05

Family

ID=27262276

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85300563A Withdrawn EP0152221A3 (fr) 1984-02-09 1985-01-28 Station terrienne pour systèmes de télécommunications par satellite

Country Status (1)

Country Link
EP (1) EP0152221A3 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0290969A2 (fr) * 1987-05-15 1988-11-17 SELENIA SPAZIO S.p.A. Antenne pliable à deux surfaces réfléchissantes
FR2656959A1 (fr) * 1989-11-28 1991-07-12 Siemens Ag Antenne pour une station terrestre de radiocommunications par satellite.
US20120249366A1 (en) * 2011-04-04 2012-10-04 Raytheon Company Communications on the move antenna system

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3646564A (en) * 1969-03-03 1972-02-29 Raytheon Co Antenna slew system
FR2359547A1 (fr) * 1976-07-20 1978-02-17 Siemens Ag Antenne de station au sol pour un systeme de transmission d'informations par satellite
EP0019775A1 (fr) * 1979-05-22 1980-12-10 Siemens Aktiengesellschaft Dispositif d'antenne, en particulier d'antenne Cassegrain

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3646564A (en) * 1969-03-03 1972-02-29 Raytheon Co Antenna slew system
FR2359547A1 (fr) * 1976-07-20 1978-02-17 Siemens Ag Antenne de station au sol pour un systeme de transmission d'informations par satellite
EP0019775A1 (fr) * 1979-05-22 1980-12-10 Siemens Aktiengesellschaft Dispositif d'antenne, en particulier d'antenne Cassegrain

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
AP-S INTERNATIONAL SYMPOSIUM, IEEE, 1975, pages 240-243, Urbana, Ill., US; H.P.COLEMAN et al.: "Low sidelobe antennas for millimeter wave communications systems" *
ICC'80 INTERNATIONAL CONFERENCE ON COMMUNICATIONS, Seattle, WA., 8th-12th June 1980, Conference Record, vol. 3 of 3, pages 36.4.1 - 36.4.5, IEEE; G.P.HECKERT: "Readily transportable earth stations for satellite communications" *
ICC'81 INTERNATIONAL CONFERENCE ON COMMUNICATIONS, Denver, Colorado, 14th-18th June 1981, Conference Record, vol. 2 of 4, pages 26.4.1 - 26.4.5, IEEE; KENICHI KAGOSHIMA et al.: "A 30/20 GHz band high-efficiency small earth-station antenna with elliptical beam" *
IEEE AP-S INTERNATIONAL SYMPOSIUM, 1977, pages 324-327, Stanford, California, US; R.B.DYBDAL et al.: "Horn antenna sidelobe reduction using absorber tunnels" *
MICROWAVE JOURNAL, vol. 23, no. 11, November 1980, pages 53-58, Dedham, Massachusetts, US; B.H.BURDINE et al.: "A low sidelobe earth station antenna for the 4/6 GHz band" *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0290969A2 (fr) * 1987-05-15 1988-11-17 SELENIA SPAZIO S.p.A. Antenne pliable à deux surfaces réfléchissantes
EP0290969A3 (fr) * 1987-05-15 1990-03-28 SELENIA SPAZIO S.p.A. Antenne pliable à deux surfaces réfléchissantes
FR2656959A1 (fr) * 1989-11-28 1991-07-12 Siemens Ag Antenne pour une station terrestre de radiocommunications par satellite.
US20120249366A1 (en) * 2011-04-04 2012-10-04 Raytheon Company Communications on the move antenna system

Also Published As

Publication number Publication date
EP0152221A3 (fr) 1986-11-05

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Inventor name: DUTTON, FRANK ALLWOOD