US3805266A - Turnstile slot antenna - Google Patents

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Classifications

• • 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
  • H01Q1/28—Adaptation for use in or on aircraft, missiles, satellites, or balloons
  • H01Q1/288—Satellite antennas
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/24—Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction
  • H01Q21/26—Turnstile or like antennas comprising arrangements of three or more elongated elements disposed radially and symmetrically in a horizontal plane about a common centre

Definitions

• a novel turnstile slot antenna is disclosed, the antenna being for and integral with a spacecraft having a substantially cylindrical body portion.
• the antenna comprises a circumferential slot about the periphery of the spacecraft body portion with an annular wave guide cavity defining a radial transmission line disposed Within the spacecraft body portion behind and in communication with the circumferential slot.
• Feed stubs and associated transmission apparatus are provided to excite the annular cavity in quadrature phase such 7 that an omnidirectional, circularly polarized, rotating radiation pattern is generated.
• the antenna of the instant invention has utility both as a transmitting and receiving device, and ensures continuous telemetry and command coverage with the spacecraft.
• This invention generally relates to antenna systems and particularly concerns an antenna system for and integral with spacecraft or missles so as to ensure telemetry and command coverage.
• the type of radiation pattern required is omnidirectional and, from the standpoint of electromagnetic theory, the type of antenna necessary to generate this requisite omnidirectional pattern is what is termed a turnstile antenna which, in its classic physical embodiment, comprises two mutually perpendicular dipoles fed 90 out-of-phase.
• the classic turnstile antenna in theory, provides circular field polarization, a zero decibel roll pattern variation, and no roll polarization, all these attributes being extremely useful in spacecraft communication.
• the classic turnstile antenna does not live up to its promise in that it does not maintain theoretical operation when on or in close proximity to a spacecraft.
• a further objective of the instant invention concerns the provision of a novel antenna structure providing high gain at substantially all look angles.”
• Yet another objective of the instant invention concerns the provision of a novel spacecraft or missle turnstile antenna which generates an extremely smooth power radiation pattern.
• the novel invention which, as afore-stated, comprises a turnstile slot antenna of novel construction, the antenna being for and integral with-a spacecraft having a substantially cylindrical body portion.
• the'antenna comprises a circumferential slot about the periphery of the spacecraft body portion with anannular wave guide cavity defining a radial tranmission line disposed within the spacecraft body portion behind and in communication with the circumferential slot.
• the annular wave guide cavity has a shorted innermost wall and is constructed to have an electrical length of approximately one-quarter the wave length of the excitation frequency.
• the annular cavity of the antenna is excited in quadrature phase by cumference of the cavity and just inside the circumferential slot. With this placement of the feed stub, the
• the short circuit defined by the innermost wall of the cavity is electrically transformed to an open circuit whereby radiation is generated outwardly through the circumferential slot.
• the radiation pattern generated is omnidirectional, circularly polarized, and defines a rotating field.
• the annular cavity is filled with a dielectric plastic honeycomb structure for strength, and the circumferential slot itself may be physically closed with a Teflon plug or seal.
• Tuning of the novel antenna of the instant invention is effected by the placement of a matching or tuning stub adjacent each of the feed stubs within the annular cavity.
• FIG. 1 is a perspective illustration of a typical spacecraft or other vehicle employing the turnstile slot antenna of the instant invention as an integral part thereof;
• FIG. 2 is an elevational view of the turnstile slot antenna of the instant invention, partially in section forillustrative clarity, taken along lines 2-2 of FIG. 1;
• FIG. 3 is a top plan view of the turnstile slot antenna of the instant invention taken along lines 3-3 of FIG. 3, and further schematically illustrating the electrical feed means utilized therewith to excite the antenna with quadrature phase.
• FIG. 1 the integral construction of the turnstile slot antenna of the instant invention with a typical spacecraft having a substantially cylindrical body portion is shown.
• the spacecraft generally designated by reference numeral may comprise an orbiting satellite such as the so-called H-model orbiting solar observatory satellite.
• the spacecraft will be seen to typically include a plurality of solar cell panels 12, an instrument package 14, and a skirt sub-assembly or substantially cylindrical body portion 16.
• body portion 16 while substantially cylindrical, is constructed as a polygon having a plurality of flat panels 18, as shown.
• a circumferential slot generally designated by reference numeral is disposed about the periphery of the substantially cylindrical spacecraft body portion 16, this circumferential slot being filled, for example, with a dielectric material such as plastic and defining the radiation surface through which the radiation pattern of the novel antenna is generated.
• annular wave guide cavity 22 designated by reference numeral 22 and defining a radial transmission line is disposed within the spacecraft body portion 16 behind and in comunication with the circumferential slot 20.
• the upper and lower walls, 24 and 26, respectively, of the annular wave guide cavity 22 are constructed of a thin sheet of metal, and it should be noted that the innermost wall or hub comprises a circular metallic disc 28 defining an electrical short circuit.
• the outermost wall of the annular cavity 22 is defined by the circumferential slot about the periphery of the spacecraft body portion 16 any may be filled with a plastic dielectric material such as is indicated at reference numeral 30.
• the novel antenna of the instant invention includes a mean to excite the annular cavity 22 in quadrature phase and, to this end, four equally spaced electrical feed stubs 32 are disposed about the circumference of the annular cavity 22 just inside the circumferential slot 20, each feed stub 32 being excited in quadrature phase such as with the schematically illustrated transmitter and phase-shifting apparatus shown in FIG. 3, and designated by reference numeral 34.
• a dielectric honeycomb filler designated by reference numeral 34 is disposed throughout the annular cavity 22 so as to provide strength, and the like.
• the preferred inventive embodiment of the novel antenna will be seen to further include a tuning stub 36 disposed in the annular cavity 22 adjacent each feed stub.
• the tuning stub 36 provides a capacitive coupling between the upper and lower walls 24 and 26, respectively, of the annular wave guide cavity 22.
• Each of the tuningstubs 36 and feed stubs 32 are preferably disposed at an equal radius from the center or hub of the annular cavity 22 and, in the preferred inventive embodiment, annular cavity 22 is contemplated to have a length or radial dimension approximating one-quarter wave length of the excitation frequency.
• an omnidirectional, circularly polarized, rotating radiation pattern is generated in an outward direction, the electric field E of the generated radiation pattern being oriented in a direction parallel to the cylindrical axis of the spacecraft body portion. Since the radiation pattern is omnidirectional in the form of a sphere, telecommunication between the ground station and the spacecraft can readily and continuously be effected, regardless of spacecraft orientation, and regardless of spin of the spacecraft.
• a turnstile slot antenna for and integral with a spacecraft having a substantially cylindrical body portion, said antenna comprising a continuous circumferential slot about the periphery of said spacecraft body portion, an annular wave guide cavity defining a continuous radial transmission line disposed within said spacecraft body portion aligned radially within said circumferential slot and in communication with said circumferential slot and having a coaxial width no greater than the coaxial width of said circumferential slot, the depth of the cavity being greater than the width and means to excite said annular cavity in quadrature phase comprising four electrical feed stubs equally spaced about the circumference of said annular cavity inside said circumferential slot and projecting from a sidewall thereof, whereby an omnidirectional circularly polarized rotating radiation pattern is generated.
• An antenna as defined in claim 2 further including a dielectric honeycomb filler disposed throughout said annular cavity.
• An antenna as defined in claim 2 further including a tuning stub disposed in said annular cavity adjacent each feed stub.
• each said tuning stub is capacitive.
• An antenna a defined in claim 1, wherein the electric field E of the generated radiation pattern is oriented in a direction parallel to the cylindrical axis of the spacecraft body portion.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Astronomy & Astrophysics (AREA)
• General Physics & Mathematics (AREA)
• Remote Sensing (AREA)
• Aviation & Aerospace Engineering (AREA)
• Waveguide Aerials (AREA)

Abstract

Description

Claims (7)

Priority Applications (1)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23125748

Family Applications (1)

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Cited By (17)

Citations (4)

• 1972
  • 1972-09-27 US US00292685A patent/US3805266A/en not_active Expired - Lifetime

Patent Citations (4)

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