US3792480A - Aerials - Google Patents

Aerials Download PDF

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Publication number
US3792480A
US3792480A US00790507A US3792480DA US3792480A US 3792480 A US3792480 A US 3792480A US 00790507 A US00790507 A US 00790507A US 3792480D A US3792480D A US 3792480DA US 3792480 A US3792480 A US 3792480A
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United States
Prior art keywords
reflector
axis
feed
main reflector
sub
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Expired - Lifetime
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US00790507A
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English (en)
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R Graham
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Individual
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Individual
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    • 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
    • H01Q19/18—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 having two or more spaced reflecting surfaces
    • H01Q19/19—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 having two or more spaced reflecting surfaces comprising one main concave reflecting surface associated with an auxiliary reflecting surface
    • H01Q19/192—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 having two or more spaced reflecting surfaces comprising one main concave reflecting surface associated with an auxiliary reflecting surface with dual offset reflectors

Definitions

  • the aerial system [51] In ⁇ .0 "6m l9/ comprises a feed, a sub-reflector and a main relfector,
  • This invention relates to precision tracking aerials, particularly the microwave aerials of the type using a concave collimating reflector.
  • the class of reflector aerials known as off-set or asymmetric reflector aerials, i.e., those in which the reflector lies to one side of the axis.
  • This type is commonly used in radar and communication systems since it enables the feed system to illuminate the whole of the reflector and the whole of the energy thus reflected can be radiated from the aerial without shadowing or obscuration by any part of the feed system.
  • This invenntion is partiuclarly concerned with the arrangement in which an off-set sub reflector is used in conjunction with a main reflector.
  • Such a system is known in which the beam from the main reflector is displaced from the'axis of the said reflector and the focus of the main reflector and also the feed are located on the axis of the main reflector.
  • This type of off-set aerial suffers from a disadvantage compared with a symmetrical aerial, i.e., one in which the feed is on the centre line of the aerial, when used for accurate tracking of a distant source or radar target.
  • the disadvantage is as follows: when the aerial feeder system is designed to receive plane polarised energy the direction of the beam axis is dependent upon the polarisation of the energy received. This is known phenomenon and is referred to as bore-sight jitter.” When such an aerial is designed to receive circular polarisation the direction of the radar axis is dependent upon the frequency of operation. This is also a known phenomenon and is referred to as frequency sensitive squint. Both of these effects are due to thefact that when the electric and magnetic fieldsemanating from thefeed have been reflected by the main reflector they are curved.
  • the present invention provides an aerial system comprising a collimating main reflector, a sub reflector and a feed positioned relative to one another so that energy passing beween the feed and the main reflector is reflected by the sub reflector and outwardly of the main reflector comprises a collimated beam having its axis offset from the axis of the main reflector, the feed being displaced from and the axis of the sub reflector being positioned transversely to the axis of the main reflector by such amounts as to substantially eliminate boresight jitter and frequency sensitive squint.
  • the sub reflector and main reflector are part hyperboloid and part paraboloid respectively but may be any suitable coacting pair of surfaces.
  • FIG. 1 illustrates a known form of off-set aerial system
  • FIG. 2 shows the curved electric and magnetic fields emanating from the main reflector of FIG. 1.
  • FIG. 3 shows diagrammetically an aerial arrangement
  • FIG. 4 shows resultant field lines produced by such an aerial.
  • the known off-set aerial system shown in FIG. 1 comprises a feed 1 which directs energy on to a sub reflector 2 where it is reflected to a main reflector 3 to produce the emergent main beam of energy 4.
  • the axis of the main reflector 3 is shown at 5 and it will be seen that the beam 4 is displaced from the axis 5 and that the focus 6 of the main reflector 3 and also the feed 1 are located on the axis 5.
  • FIG. 3 An improved system according to the present invention is shown in FIG. 3. This system can, in the usual way, be used both to receive and to radiate energy.
  • the main reflector 10 is a part paraboloid concave collimating reflector and the final offset collimated beam 11 leaving this reflector has an axis 12 parallel to the axis 13 of the main reflector.
  • the feed 14 is effectively a point source radiating a divergent beam 15 which is reflected from the surface of a part hyperboloid sub reflector 16 onto the main reflector to produce the beam 11.
  • the feed 14 is located on the axis 17 of the hyperboloid, the latter having one of its foci coinciding with the feed and its other focus coinciding with the focus 18 of the main reflector. It will be ssen that in this arrangement, as compared with the arrangement of FIG.
  • the sub reflector l6 and the feed 14 have been rotated about the focus 18 so that the feed is displaced from and the axis of the sub reflector is transverse to the axis 13 of the main reflector. This necessitates extending the upper edge of the hyperboloid surface so that a different portion of the sub reflector 16 is used. As seen in FIG. 4, the distortion produced in the field lines shown in FIG. 2 has been substantially eliminated.
  • the sub reflector 16 and main reflector 10 would normally be hyperbolic and parabolic respectively and only this type is described by way of example, however, this is not essential and any suitably coacting pair of surfaces could be used.
  • the displacement of the feed from the axis can be optimised to give the minimum distortion consistent with the other chosen parameters.
  • the feed is normally orientated so that the energy is directed towards the centre of the reflectors.
  • a horn feed is normally used since it may be designed to illuminate the reflectors efficiently.
  • An example of an aerial arrangement according to the invention with minimal polarisation distortion has the following parameters:
  • An aerial system comprising a collimating main reflector, a sub reflector and a feed positioned relative to one another so that energy passing between the feed and the main reflector is reflected by the sub reflector and outwardly of the main reflector comprises a collimated beam, having its axis offset from the axis of the main reflector, the feed being displaced from and the axis of the sub reflector being positioned transversely to the axis of the main reflector by such amounts as to substantially eliminate boresight jitter, and frequency sensitive squint.
  • An aerial system in which the focal length of the main reflector is units, the eccentricity of the sub reflector is 1.85, the region of the main reflector extends from 40 to units from its axis measured in a direction normal thereto, the distance of the feed from the focus of the main reflector is 100 units, the feed is displaced from the axis of the main reflector by a 4 rotation about the main reflector focus and the feed is orientated to have a beam axis in clined at 15 with respect to the sub reflector axis.

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  • Aerials With Secondary Devices (AREA)
US00790507A 1968-01-02 1968-12-31 Aerials Expired - Lifetime US3792480A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB27468 1968-01-02

Publications (1)

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US3792480A true US3792480A (en) 1974-02-12

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US00790507A Expired - Lifetime US3792480A (en) 1968-01-02 1968-12-31 Aerials

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US (1) US3792480A (nl)
DE (1) DE1817585A1 (nl)
FR (1) FR1605256A (nl)
GB (1) GB1331221A (nl)
NL (1) NL6818798A (nl)

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3914768A (en) * 1974-01-31 1975-10-21 Bell Telephone Labor Inc Multiple-beam Cassegrainian antenna
US3949404A (en) * 1974-12-19 1976-04-06 Nasa Highly efficient antenna system using a corrugated horn and scanning hyperbolic reflector
US3953858A (en) * 1975-05-30 1976-04-27 Bell Telephone Laboratories, Incorporated Multiple beam microwave apparatus
US3995275A (en) * 1973-07-12 1976-11-30 Mitsubishi Denki Kabushiki Kaisha Reflector antenna having main and subreflector of diverse curvature
DE2636142A1 (de) * 1975-08-20 1977-03-03 Vaclav Josef Vokurka Antenne
DE2732419A1 (de) * 1976-07-22 1978-03-09 Vaclav Josef Vokurka Antenne fuer messzwecke
US4145695A (en) * 1977-03-01 1979-03-20 Bell Telephone Laboratories, Incorporated Launcher reflectors for correcting for astigmatism in off-axis fed reflector antennas
US4272769A (en) * 1979-08-27 1981-06-09 Young Frederick A Microwave antenna with parabolic main reflector
US4339757A (en) * 1980-11-24 1982-07-13 Bell Telephone Laboratories, Incorporated Broadband astigmatic feed arrangement for an antenna
US4343004A (en) * 1980-11-24 1982-08-03 Bell Telephone Laboratories, Incorporated Broadband astigmatic feed arrangement for an antenna
US4407001A (en) * 1981-10-02 1983-09-27 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Focal axis resolver for offset reflector antennas
US4482898A (en) * 1982-10-12 1984-11-13 At&T Bell Laboratories Antenna feed arrangement for correcting for astigmatism
US4491848A (en) * 1982-08-30 1985-01-01 At&T Bell Laboratories Substantially frequency-independent aberration correcting antenna arrangement
US4535338A (en) * 1982-05-10 1985-08-13 At&T Bell Laboratories Multibeam antenna arrangement
EP0168904A1 (en) * 1984-02-24 1986-01-22 Nippon Telegraph And Telephone Corporation Offset-fed dual reflector antenna
US6225961B1 (en) 1999-07-27 2001-05-01 Prc Inc. Beam waveguide antenna with independently steerable antenna beams and method of compensating for planetary aberration in antenna beam tracking of spacecraft
US6417602B1 (en) 1998-03-03 2002-07-09 Sensotech Ltd. Ultrasonic transducer

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3209513A1 (de) * 1982-03-16 1984-02-09 ANT Nachrichtentechnik GmbH, 7150 Backnang Exzentrische parabolantenne mit geringer kreuzpolarisation
DE3224257A1 (de) * 1982-06-28 1983-12-29 Siemens AG, 1000 Berlin und 8000 München Mikrowellen-richtfunkantenne

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3332083A (en) * 1963-06-14 1967-07-18 Csf Cassegrain antenna with offset feed

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3332083A (en) * 1963-06-14 1967-07-18 Csf Cassegrain antenna with offset feed

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3995275A (en) * 1973-07-12 1976-11-30 Mitsubishi Denki Kabushiki Kaisha Reflector antenna having main and subreflector of diverse curvature
US3914768A (en) * 1974-01-31 1975-10-21 Bell Telephone Labor Inc Multiple-beam Cassegrainian antenna
US3949404A (en) * 1974-12-19 1976-04-06 Nasa Highly efficient antenna system using a corrugated horn and scanning hyperbolic reflector
US3953858A (en) * 1975-05-30 1976-04-27 Bell Telephone Laboratories, Incorporated Multiple beam microwave apparatus
DE2636142A1 (de) * 1975-08-20 1977-03-03 Vaclav Josef Vokurka Antenne
DE2732419A1 (de) * 1976-07-22 1978-03-09 Vaclav Josef Vokurka Antenne fuer messzwecke
US4208661A (en) * 1976-07-22 1980-06-17 Vokurka Vaclav J Antenna with two orthogonally disposed parabolic cylindrical reflectors
US4145695A (en) * 1977-03-01 1979-03-20 Bell Telephone Laboratories, Incorporated Launcher reflectors for correcting for astigmatism in off-axis fed reflector antennas
US4272769A (en) * 1979-08-27 1981-06-09 Young Frederick A Microwave antenna with parabolic main reflector
US4339757A (en) * 1980-11-24 1982-07-13 Bell Telephone Laboratories, Incorporated Broadband astigmatic feed arrangement for an antenna
US4343004A (en) * 1980-11-24 1982-08-03 Bell Telephone Laboratories, Incorporated Broadband astigmatic feed arrangement for an antenna
US4407001A (en) * 1981-10-02 1983-09-27 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Focal axis resolver for offset reflector antennas
US4535338A (en) * 1982-05-10 1985-08-13 At&T Bell Laboratories Multibeam antenna arrangement
US4491848A (en) * 1982-08-30 1985-01-01 At&T Bell Laboratories Substantially frequency-independent aberration correcting antenna arrangement
US4482898A (en) * 1982-10-12 1984-11-13 At&T Bell Laboratories Antenna feed arrangement for correcting for astigmatism
EP0168904A1 (en) * 1984-02-24 1986-01-22 Nippon Telegraph And Telephone Corporation Offset-fed dual reflector antenna
US6417602B1 (en) 1998-03-03 2002-07-09 Sensotech Ltd. Ultrasonic transducer
US6225961B1 (en) 1999-07-27 2001-05-01 Prc Inc. Beam waveguide antenna with independently steerable antenna beams and method of compensating for planetary aberration in antenna beam tracking of spacecraft
US6246378B1 (en) 1999-07-27 2001-06-12 Prc, Inc. Beam waveguide antenna with independently steerable antenna beams and method of compensating for planetary aberration in antenna beam tracking of spacecraft

Also Published As

Publication number Publication date
DE1817585A1 (de) 1974-08-01
GB1331221A (en) 1973-09-26
NL6818798A (nl) 1973-08-27
FR1605256A (nl) 1973-11-02

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