US2884630A - Aerial assembly - Google Patents

Aerial assembly Download PDF

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Publication number
US2884630A
US2884630A US647899A US64789957A US2884630A US 2884630 A US2884630 A US 2884630A US 647899 A US647899 A US 647899A US 64789957 A US64789957 A US 64789957A US 2884630 A US2884630 A US 2884630A
Authority
US
United States
Prior art keywords
reflector
aerial
radiation
main reflector
plates
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
US647899A
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English (en)
Inventor
Arthur G G H Robinson
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.)
EK Cole Ltd
Original Assignee
EK Cole Ltd
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 EK Cole Ltd filed Critical EK Cole Ltd
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Publication of US2884630A publication Critical patent/US2884630A/en
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Classifications

    • 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
    • H01Q3/14—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 the relative position of primary active element and a refracting or diffracting device
    • 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
    • H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
    • H01Q25/002—Antennas or antenna systems providing at least two radiating patterns providing at least two patterns of different beamwidth; Variable beamwidth antennas
    • 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
    • H01Q3/01—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the shape of the antenna or antenna system

Definitions

  • micro-wave aerial assemblies consist of a wave guide or co-axial feed which directs the microwave radiation at a reflector, and a dipole aerial may be used in conjunction with the wave guide or co-axial feed.
  • the term aerial will be used hereafter as a general description of the source from which transmitted radiation is directed at a reflector in an aerial assembly.
  • a particular application of the invention is to an aerial assembly for an airborne search radar system, where it is required to have a pattern of radiation in the form of a pencil beam for the location of airborne objects and an alternative pattern of radiation in the form of a beam obeying the cosecant-squared law for eflicient map reading of the ground below.
  • a feature of my invention is a micro-wave aerial assembly for providing at least two alternative required patterns of radiation, comprising an aerial, a main reflector for determiningone of said required patterns of radiation, an auxiliary reflector, and means for effecting movement of the auxiliary reflector, through the main reflector, between two alternative positions, in a first of which the main reflector is located between the auxiliary reflector and the areial and in which the auxiliary reflector has negligible eflect on the required pattern of radiation determined by the main reflector and in the second of which positions the auxiliary reflector is located between the main reflector and the aerial and determines an alternative required pattern of radiation.
  • Figure 1 is a diagrammatic front elevation of an aerial assembly constructed on known principles
  • Figure 2 is a sectional side elevation of the reflector portions thereof.
  • Figure 3 is a similar view to Figure 2, but showing one embodiment of my invention.
  • Figures 4 and 5 show a sectional side elevation and a rear elevation respectively of another embodiment of my invention.
  • an aerial A (not shown in detail), with the electric vector E orientated in the direction shown by the arrow, is mounted at or near the focal point of a main reflector B designed according to known principles to produce one required pattern of radiation.
  • An auxiliary reflector C in the form of a series of thin parallel plates is mounted within the main reflector B. These plates are successively spaced apart by less than one-half wavelength and have leading edges which determine an alternative required pattern of radiation when the plates are positioned with respect to the feed from A so that the voltage vector of the incident radiation is parallel to them (as in Figure 1). Under these conditions, the plates behave as wave guides beyond cut-off and radiation is reflected from them in the vicinity of their leading edges.
  • This change of relative position between the aerial A and the auxiliary reflector C can be effected by causing A or C to be rotatable.
  • FIG. 3 One embodiment of the invention is shown in Figure 3.
  • the main reflector B has vertical narrow slots through which may pass the plates of the auxiliary reflector C, the aerial (not shown) being mounted at or near the focal point of the main reflector B.
  • a front elevation would be the same as Figure 1, the plates of reflector C protruding between the main reflector and the aerial, so that the auxiliary reflector determines the alternative required pattern of radiation, whereas by swinging the plates about a pivot D, the reflector C may be moved to a position to the rear of the main reflector, as in Figure 3, where C has negligible effect on the pattern of radiation determined by the main reflector B.
  • the slots are very narrow compared with wavelength and are parallel to the voltage vector of the incident radiation. The slots thus have negligible effect on the pattern of radiation determined by the main reflector.
  • the auxiliary reflector C may be in the form of a grating and its movement may be eflfected alternatively by sliding the plates through the slots in the main reflector instead of pivoting them as in the assembly of Figure 3. Such an arrangement is shown in Figures 4 and 5, in which the auxiliary reflector C slides on guides F through the main reflector B.
  • the pattern of radiation from the aerial determined by the main reflector may be in the form of a pencil beam and the alternative pattern of radiation determined by the auxiliary reflector may be in the form of a beam obeying the so-called cosecant-squared law.
  • This invention is also applicable to aerial assemblies in which the auxiliary reflector is so large that it is impracticable to rotate it according to known methods of beam switching, and where it is not permissible to rotate the feed because of unwanted effects from the resultant change of polarisation.
  • a micro-wave aerial assembly for providing at least two alternative required patterns of radiation, comprising an aerial, a main reflector for determining one of said required patterns of radiation, an auxiliary reflector, and means for effecting movement of the auxiliary reflector, through the main reflector, between two alternative positions, in a first of which the main reflector is located between the auxiliary reflector and the aerial and in which the auxiliary reflector has negligible effect on the required pattern of radiation determined by the main reflector and in the second of which positions the auxiliary reflector is located between the main reflector and the aerial and determines an alternative required pattern of radiation.
  • An aerial assembly according to claim 1, comprising pivoting means near an edge of the main reflector, the auxiliary reflector being pivotable about said pivoting means between said first and second positions.
  • An aerial assembly according to claim 1, comprising means for slidably moving the auxiliary reflector through the main reflector between said first and second positions.
  • auxiliary reflector comprises a plurality of thin plates having leading edges which determine the reflecting surface, said plates being substantially parallel and being successively spaced apart by a distance less than one-half wavelength, the main reflector having narrow slots through which the plates are movable, and in which radiation transmitted by the aerial has a voltage vector which is parallel with said plates.
  • auxiliary reflector comprises a plurality of thin plates having leading edges which determine the reflecting surface, said plates being substantially parallel and being successively spaced apart by a distance less than onehalf wavelength, the main reflector having narrow slots through which the plates are movable, and in which radiation transmitted by the aerial has a voltage vector which is parallel with said plates.

Landscapes

  • Aerials With Secondary Devices (AREA)
  • Variable-Direction Aerials And Aerial Arrays (AREA)
US647899A 1956-03-27 1957-03-22 Aerial assembly Expired - Lifetime US2884630A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2884630X 1956-03-27

Publications (1)

Publication Number Publication Date
US2884630A true US2884630A (en) 1959-04-28

Family

ID=10917137

Family Applications (1)

Application Number Title Priority Date Filing Date
US647899A Expired - Lifetime US2884630A (en) 1956-03-27 1957-03-22 Aerial assembly

Country Status (3)

Country Link
US (1) US2884630A (fr)
DE (1) DE1051918B (fr)
FR (1) FR1173344A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4851858A (en) * 1984-01-26 1989-07-25 Messerschmitt-Boelkow-Blohm Gmbh Reflector antenna for operation in more than one frequency band

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2570197A (en) * 1949-06-16 1951-10-09 John I Bohnert Dual purpose antenna
US2790169A (en) * 1949-04-18 1957-04-23 Itt Antenna

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2680810A (en) * 1952-02-12 1954-06-08 Us Army Microwave antenna system

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2790169A (en) * 1949-04-18 1957-04-23 Itt Antenna
US2570197A (en) * 1949-06-16 1951-10-09 John I Bohnert Dual purpose antenna

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4851858A (en) * 1984-01-26 1989-07-25 Messerschmitt-Boelkow-Blohm Gmbh Reflector antenna for operation in more than one frequency band

Also Published As

Publication number Publication date
FR1173344A (fr) 1959-02-24
DE1051918B (de) 1959-03-05

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