US3392397A - Cassegrain antenna for scanning with elliptically shaped beam - Google Patents

Cassegrain antenna for scanning with elliptically shaped beam Download PDF

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Publication number
US3392397A
US3392397A US527549A US52754966A US3392397A US 3392397 A US3392397 A US 3392397A US 527549 A US527549 A US 527549A US 52754966 A US52754966 A US 52754966A US 3392397 A US3392397 A US 3392397A
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United States
Prior art keywords
reflector
antenna
subdish
elliptically shaped
microwave energy
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.)
Expired - Lifetime
Application number
US527549A
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English (en)
Inventor
Schwartz Leonard
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 Precision Systems Inc
Original Assignee
General Precision Systems Inc
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
Application filed by General Precision Systems Inc filed Critical General Precision Systems Inc
Priority to US527549A priority Critical patent/US3392397A/en
Priority to NO166319A priority patent/NO122793B/no
Priority to GB1618/67A priority patent/GB1136174A/en
Priority to DE19671591132 priority patent/DE1591132A1/de
Priority to SE01712/67A priority patent/SE335756B/xx
Priority to FR94381A priority patent/FR1510730A/fr
Priority to DK74967AA priority patent/DK117577B/da
Application granted granted Critical
Publication of US3392397A publication Critical patent/US3392397A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/20—Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/24—Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave constituted by a dielectric or ferromagnetic rod or pipe
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/12—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical relative movement between primary active elements and secondary devices of antennas or antenna systems
    • H01Q3/16—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical relative movement between primary active elements and secondary devices of antennas or antenna systems for varying relative position of primary active element and a reflecting device
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/12—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical relative movement between primary active elements and secondary devices of antennas or antenna systems
    • H01Q3/16—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical relative movement between primary active elements and secondary devices of antennas or antenna systems for varying relative position of primary active element and a reflecting device
    • H01Q3/20—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical relative movement between primary active elements and secondary devices of antennas or antenna systems for varying relative position of primary active element and a reflecting device wherein the primary active element is fixed and the reflecting device is movable

Definitions

  • the present invention relates to antennas for directionally transmitting radio frequency (RF) energy in a particular shape beam.
  • RF radio frequency
  • One aspect of the present invention relates to a novel antenna arrangement for propagating an elliptically shaped beam of RF energy.
  • Another aspect relates to a novel compact antenna arrangement for independently propagating each of three separate beams by a composite, compact antenna.
  • a further aspect relates to a novel antenna arrangement for propagating an elliptical beam and rotating the elliptical beam while maintaining the orientation of the elliptical shape.
  • the novel antenna system described herein directionally transmits an elliptical shaped beam which is conically scanned, thus rotating the elliptical beam in a circle.
  • This beam is referred to as the main beam.
  • the present state of the art is such that side lobes of RF adjacent to the transmitted beam are not eliminated by antenna design.
  • the antenna system includes the generation of two elliptical auxiliary beams positioned respectively at the sides of the main beam which may essentially blanket the side lobes of the main beam.
  • the novel antenna system is a composite antenna of at least two different types combined in compact arrangement.
  • One of the antennas may be referred to as a Cassegrainian type antenna while another of the antennas of the composite system may be referred to as a hornreflector arrangement.
  • the main beam is propagated by the Cassegrainian type antenna which employs the novel combination of a dielectric rod feed, which is tapered along the major part of its length.
  • the feed appears through the vertix of a modified parabolic reflector or main dish and directs RF energy to an eccentrically rotated hyperboloidal reflector or subdish.
  • the feed is particularly located at one focal point of the hyperbolic reflector and the hyperbolic reflector images the real source of RF into a virtual source at its other focal point, the other focal point being coincident with the focal point of the parabolic reflector.
  • the elliptical shape of the propagated beam may be provided in any one of several ways: feed modification; subdish modification or main dish modification, the latter being the preferred method and the arrangement with which the present application is concerned.
  • An elliptically shaped beam may be provided by providing an unmodified feed and subdish arrangement and providing a main dish having a substantially elliptical configuration, from a plan view.
  • the desired structure of the main dish may be provided by modifying a parabolic reflector by reducing the aperture dimension of the reflector in the azimuth plane.
  • the resulting pattern will have a beam width equal to:
  • K is a constant determined by the illumination taper at the edge of the aperture; 7 ⁇ is the wave length of the RF energy and D is the length of the minor axis.
  • the main antenna of the complex, compact antenna system provides a scanned beam from a feed which produces a circular radiation pattern which illuminates an eccentrically driven hyperboloidal reflector which re- 3,392,397 Patented July 9, 1968 radiates the power into a generally elliptically shaped (modified) parabolic reflector.
  • the beam is scanned by rotating the hyperboloid or subdish so that its center makes a circle about the focus of the Paraboloid.
  • the amount of eccentricity (radius of the circle) determines the squint angle of the emerging beam.
  • the condition for minimum aperture blocking occurs When the front blocking of the subdish is made substantially equal to the back blocking of the feed.
  • the minimum blocking diameter is given by the expression:
  • D min. is the diameter of the subdish
  • k is the ratio of effective feed aperture diameter to its blocking diameter
  • F is the focal length of the parabolic reflector
  • A is the operating wave length of the RF energy.
  • a Cassegrainian type antenna may be provided for propagating a conically scanned elliptical beam of energy.
  • Another object is to provide an antenna arrangement for propagating an elliptical beam of RF energy and for rotating the elliptical beam while maintaining the same orientation of the elliptical shape.
  • Another object is to provide a composite compact antenna system for transmitting a conically scanned elliptical beam with two auxiliary elliptically shaped beams also transmitted by the same system for covering adjacent side lobes on either side of the main beam.
  • FIG. 1 is a plan view of the main dish with details of the auxiliary antenna feeds omitted for the sake of clarity, and
  • FIG. 2 is a cross-section view, from the side of the composite antenna system for propagating a conically scanned elliptical beam and two auxiliary elliptical beams.
  • the surface contour of the main dish or main reflector is illustrated with the major diameter D and minor diameter D indicating the major and minor diameters of the reflector, respectively.
  • the circle 12 has its center at the axis of the diameters and illustrates the path of the center of the subdish 10 in its rotational movement.
  • the arrows 11 represent the eccentric movement or rotation of the subdish 10.
  • FIG. 1 illustrates one method of forming the elliptical structure of the reflector D/D' from a round parabolic reflector, such as represented by 14.
  • the cross-hatched areas of 15a and 1512 may be covered with a microwave absorbing material.
  • the equations provided may be used for mathematically determining the minor diameter D' and the contour of the sides of the elliptically shaped reflection area.
  • the length and width measurements of the beam will be determined by the size of the reflector and the surface or plan and side or profile contours of the reflector.
  • a beam having an elevation width of 3.20 degrees and an azimuth width of 4.7 degrees "4 has been provided by the arrangement shown Where a parabolic reflector, such as 14, had a major diameter D measuring 18 inches with the sides of the elliptically shaped reflector extending to a minor diameter D measuring 8 inches.
  • FIG. 1 has omitted apparatus for propagating the auxiliary or cover beams. This has been omitted for the sake of clarity.
  • the motor employed for rotating the subdish 10 and a network for suspending the motor and subdish have also been omitted.
  • the dielectric rod feed is hidden by the subdish 10. The omitted components may be seen in the profile view in FIG. 2.
  • the reflectors for each of the auxiliary beams may be positioned in the unused areas 15a and 15b of the parabolic reflector 14.
  • the feed may be in the form of a wave guide horn, one horn for each reflector, positioned to illuminate the particular reflector for providing the auxiliary beams.
  • FIG. 2 illustrates a profile view along line AA of a composite, compact antenna system positioned within a parabolic reflector, part of which is used as part of the antenna for transmitting the main beam.
  • the sections 15a and 15b in FIG. 2 correspond to the identically labeled sections in FIG. 1.
  • the minor diameter D is shown in profile location on the parabolic reflector 14 and corresponds to the minor diameter D' in FIG. 1.
  • sectors of another parabolic reflector may be positioned above the areas 15a and 15b such as shown by and 15d, respectively.
  • the other parabolic reflector, from which the sectors, represented by 150 and 15d, may be cut, would be a reflector substantially physically similar to reflector 14.
  • each sector 15c and 15d may be tilted, for example, some 7.
  • Radio frequency energy is fed by open wave guide horns 20 and 21, respectively, each positioned above the reflector sector with which it is associated and each tilted some 30", for example, in opposite directions.
  • the sector forming the reflector (150 or 15d) need not be exactly physically symmetrical, in plan form, as is desired of the main dish of the main antenna.
  • the sectors 15c and 15d may be substantially corresponding to the shape of the areas 15a and 1512 respectively.
  • each of the horns 20 and 21 may be in the form of a dual horn.
  • each of the horns 20 and 21 is in the form of a pyramidal horn with an E plane bifurcation. This may be formed by a septum 22 which serves to split the power propagating into the horn into two equal parts so that at the exit aperture there are essentially two-in-phase horns sideby-side.
  • This construction positions the phase center of each horn of the dual horn at different offset distances from the focal point of the parabola sector so that the peak of each beam propagated by the dual horn arrangement will occur at a different azimuth angle producing a wider pattern than obtainable from a single horn of the same combined aperture.
  • Each of the horns, 20 and 21, also includes its respective wave guide line for conducting microwave energy from a source (not shown) to the horn.
  • FIG. 2 Also shown in FIG. 2 is a representation of a motor 16 for driving the subdish 10.
  • a shaft, 17, couples the motor 16 to the subdish 10 and, as will be readily seen, such coupling is at an off-center position of the subdish.
  • the subdish is rotated eccentrically about the axis of the diameters D and D' as indicated in FIG. 1.
  • the dielectric rod feed 18 is also shown, positioned at the center position along diameters D and D.
  • the composite, complex antenna assembly may also include a radome, not shown, for protecting the apparatus from the elements.
  • the motor 16 and subdish must be suspended in some manner so as to hold the motor and subdish in position. This may be accomplished by a cross network of rods which are sufficiently small in diameter so as not to undesirably interfere with energy radiated from the antenna assembly, but sufliciently strong to support the motor and subdish and hold such components in place.
  • a preferred network may consist of at least four support rods (two of which 24 and 25 are shown) supporting a collar or frame 26 which may support the motor 16.
  • the subdish 10 would then be supported by the shaft 17 which serves also to rotate the subdish.
  • an antenna for transmitting an elliptical beam (an unscanned beam) may be made by slightly modifying the arrangement shown.
  • the hyperboloid reflector 10 were positioned so that its center were in coincidence with the axis or crossing point of the diameter -D and D of the parabolic reflector 14 and the means for rotating the hyperboloid reflector 10 were eliminated then an antenna for propagating a highly directional elliptically shaped beam is provided.
  • a microwave energy antenna for directionally transmitting a conically scanned elliptically shaped beam of microwave energy including;
  • a modified parabolic reflector having the aperture dimension of said reflector reduced in the azimuth plane for providing a beam width equal to where K is a constant determined by the illumination taper at the edge of the aperture, A is the wave length of said microwave energy and D is the length of the minor axis,
  • a hyperboloidal reflector positioned above said modified reflector and at the focal point thereof for radiating energy to saidmodified reflector.
  • a dielectric rod feed positioned on the axis of said modified reflector for radiating microwave energy to said hyperboloidal reflector
  • a microwave energy antenna system for directionally transmitting a conically scanned elliptically shaped beam of microwave energy and at least two auxiliary beams azimuthly positioned for covering side lobes of the conically scanned elliptically shaped beam including;
  • a modified parabolic reflector having the aperture di- 6 mension thereof reduced in the azimuth plane for providing a beam width equal towhere K is a constant determined by the illumination taper at the edge of the aperture, A is the wave length of the microwave energy and D is the length of the minor axis,
  • a hyperboloidal reflector positioned at the focal point of the said modified reflector for radiating microwave energy to said modified reflector
  • a dielectric rod positioned on the axis of said modified reflector for radiating microwave energy to the radiating surface of said hyperboloidal reflector
  • first and second auxiliary reflectors each having substantially the same configuration as said modified reflector, the minor axis of said first and second auxiliary reflector and said modified reflector being substantially parallel and aligned,
  • means including a wave guide horn for radiating microwave energy on to the reflecting surface of said first auxiliary reflector for propagating a beam of microwave energy in an elliptically shaped configuration and positioned adjacent one side of the said scanned beam, and
  • means including a second wave guide horn for radiating microwave energy on the reflecting surface of said second auxiliary reflector for propagating a second beam of microwave energy in an elliptically shaped configuration and positioned adjacent the other side of the said scanned beam.

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US527549A 1966-02-15 1966-02-15 Cassegrain antenna for scanning with elliptically shaped beam Expired - Lifetime US3392397A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
US527549A US3392397A (en) 1966-02-15 1966-02-15 Cassegrain antenna for scanning with elliptically shaped beam
NO166319A NO122793B (enrdf_load_stackoverflow) 1966-02-15 1967-01-09
GB1618/67A GB1136174A (en) 1966-02-15 1967-01-11 Improvements in antennae
DE19671591132 DE1591132A1 (de) 1966-02-15 1967-01-24 Vorrichtung zur UEbertragung eines elliptisch geformten Strahles
SE01712/67A SE335756B (enrdf_load_stackoverflow) 1966-02-15 1967-02-07
FR94381A FR1510730A (fr) 1966-02-15 1967-02-09 Dispositif pour transmettre un faisceau elliptique d'énergie haute-fréquence
DK74967AA DK117577B (da) 1966-02-15 1967-02-10 Antenneenhed.

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US527549A US3392397A (en) 1966-02-15 1966-02-15 Cassegrain antenna for scanning with elliptically shaped beam

Publications (1)

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US3392397A true US3392397A (en) 1968-07-09

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Application Number Title Priority Date Filing Date
US527549A Expired - Lifetime US3392397A (en) 1966-02-15 1966-02-15 Cassegrain antenna for scanning with elliptically shaped beam

Country Status (7)

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US (1) US3392397A (enrdf_load_stackoverflow)
DE (1) DE1591132A1 (enrdf_load_stackoverflow)
DK (1) DK117577B (enrdf_load_stackoverflow)
FR (1) FR1510730A (enrdf_load_stackoverflow)
GB (1) GB1136174A (enrdf_load_stackoverflow)
NO (1) NO122793B (enrdf_load_stackoverflow)
SE (1) SE335756B (enrdf_load_stackoverflow)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4041500A (en) * 1976-05-12 1977-08-09 The United States Of America As Represented By The Secretary Of The Navy Line scan radar antenna using a single motor
US4761655A (en) * 1984-11-30 1988-08-02 British Telecommunications Plc Transportable antenna for an earth station
US5402137A (en) * 1992-09-17 1995-03-28 Hughes Aircraft Company Equalized shaped reflector antenna system and technique for equalizing same

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5028148B1 (enrdf_load_stackoverflow) * 1969-11-28 1975-09-12
EP0507440A1 (en) * 1991-02-25 1992-10-07 Gerald Alexander Bayne Antenna
CA2198969A1 (en) * 1996-03-04 1997-09-04 Andrew Corporation Broadband omnidirectional microwave antenna with decreased sky radiation and with a simple means of elevation-plane pattern control
GB2326530B (en) * 1997-04-22 2001-12-19 Andrew Corp A broadband omnidirectional microwave parabolic dish shaped cone antenna

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2531454A (en) * 1942-02-04 1950-11-28 Sperry Corp Directive antenna structure

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2531454A (en) * 1942-02-04 1950-11-28 Sperry Corp Directive antenna structure

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4041500A (en) * 1976-05-12 1977-08-09 The United States Of America As Represented By The Secretary Of The Navy Line scan radar antenna using a single motor
US4761655A (en) * 1984-11-30 1988-08-02 British Telecommunications Plc Transportable antenna for an earth station
US5402137A (en) * 1992-09-17 1995-03-28 Hughes Aircraft Company Equalized shaped reflector antenna system and technique for equalizing same

Also Published As

Publication number Publication date
FR1510730A (fr) 1968-01-19
GB1136174A (en) 1968-12-11
NO122793B (enrdf_load_stackoverflow) 1971-08-16
DK117577B (da) 1970-05-11
SE335756B (enrdf_load_stackoverflow) 1971-06-07
DE1591132A1 (de) 1970-01-08

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