Classifications

• • 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
  • H01Q13/08—Radiating ends of two-conductor microwave transmission lines, e.g. of coaxial lines, of microstrip lines
• • 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
  • H01Q13/02—Waveguide horns
  • H01Q13/0275—Ridged horns
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q5/00—Arrangements for simultaneous operation of antennas on two or more different wavebands, e.g. dual-band or multi-band arrangements
  • H01Q5/40—Imbricated or interleaved structures; Combined or electromagnetically coupled arrangements, e.g. comprising two or more non-connected fed radiating elements
  • H01Q5/45—Imbricated or interleaved structures; Combined or electromagnetically coupled arrangements, e.g. comprising two or more non-connected fed radiating elements using two or more feeds in association with a common reflecting, diffracting or refracting device
  • H01Q5/47—Imbricated or interleaved structures; Combined or electromagnetically coupled arrangements, e.g. comprising two or more non-connected fed radiating elements using two or more feeds in association with a common reflecting, diffracting or refracting device with a coaxial arrangement of the feeds

Definitions

• This invention relates generally to antennas and more particularly to a coaxial cavity antenna.
• Coaxial antennas have been produced for some time. However, they have all suffered from electrical plane ("E- plane”) and magnetic plane ("H-plane”) pattern differences. Specifically, in a typical coaxial radiator, differences in the aperture distributions of the E & H planes cause the E- plane pattern to narrow as frequency increases. This narrowing is not desirable in a dual polarized antenna, that is, the net result is wide azimuth/narrow elevation for one sense of polarization and narrow azimuth/wide elevation for the other sense of polarization. For the case of the dual circularly polarized coaxial antenna, this is undesirable as it results in unacceptable axial ratio performance. Similarly, for a dual linearly polarized coaxial antenna, E & H plane pattern differences result in unacceptable differences in field of view coverage. The differences in the E & H plane patterns also limits the useful operating bandwidth.
• E- plane electrical plane
• H-plane magnetic plane
• the present invention provides a coaxial cavity antenna that addresses shortcomings of prior systems and methods .
• the invention provides numerous technical advantages. For example, the problem of a narrow E-plane has been minimized in an antenna in accordance with the present invention.
• the antennas of the present invention exhibit substantially symmetric E-plane and H-plane performance over reasonably wide angles, such as ⁇ 60 degrees, and over reasonably wide frequency bandwidths, such as an octave per sub-band.
• Another advantage of the present invention is that the antennas are scalable, and through the appropriate choice of inner to outer cavity sizes and depths can be nested in a concentric configuration to provide multi- octave performance.
• Antennas in accordance with the present invention have been constructed having bandwidths of 0.5 to 2.0 GHz, 2.0 to 8.0 GHz, and even the whole 2.0 to 18.0 GHz range.
• Antennas in accordance with the present invention have applications as elements in interferometers, polarimetry antennas, and as various types of reflector feeds.
• Antennas incorporating the present invention have excellent dispersion properties making them excellent time domain antennas for use in very wideband systems.
• Antennas in accordance with the present invention can be arrayed in vertical stacks in order to provide increased directivity (gain) by narrowing the elevation beamwidth.
• antennas in accordance with the present invention have few mechanical parts, and are relatively simple to machine and assemble, and have proven to be repeatable.
• FIGURE 1 is an isometric view of a coaxial cavity antenna representing an embodiment of the present invention
• FIGURE 6 is a diagram illustrating an antenna feed network for use in conjunction with an antenna of the present invention.
• FIGURE 12 is an isometric view of a vertical array of coaxial cavity antennas represented by the embodiments of FIGURES 1-3; and
• FIGURE 13 is an isometric view of a line array of coaxial cavity antennas represented by the embodiments of FIGURES 1-3.
• the outer conductor 14 includes an aperture ring 22 and a base 15.
• Aperture ring 22 can be formed integral with base 15 or it can be a separate part and detachable from base 15.
• aperture ring 22 has an outer diameter equal to the outer diameter of base 15.
• aperture ring 22 and base 15 are formed such that aperture ring 22 can be securely attached to base 15.
• FIGURE 7 An exploded view of such an embodiment is illustrated in FIGURE 7.
• Aperture ring 22 includes a plurality of aperture teeth 24 that are radially oriented and disposed around the inside diameter of the aperture ring.
• aperture teeth 24 are triangular in shape, and are equally spaced around the inside diameter of aperture ring 22 with each aperture tooth oriented generally radially towards axis 50 of the coaxial cavity antenna 10.
• One purpose of aperture teeth 24 is for pattern control. More specifically aperture teeth 24 function to make the E-plane and H-plane performance substantially symmetric over reasonably wide angles such as ⁇ 60 degrees.
• Polarization diversity is achieved through the use of a feed network.
• feed networks 310 and 320 are illustrated in FIGURE 6.
• the use of a feed network can produce either two orthogonal linear polarizations or both senses of circular polarization (right-handed and left- handed) .
• two 180 degree hybrids 340 are utilized for either case, and a 90 degree hybrid 350 is added behind hybrids for feed network 320 to get dual circular polarization.
• the TE11 coaxial mode is excited by feeding signals from oppositely spaced coaxial feed terminals 330a and 330b with equal amplitude and a 180 phase shift relative to one another into 180 degree hybrids 340.
• the output of 180 degree hybrids 340 each provide one sense of linear polarization.
• the delta port is terminated.
• the signals from the four coaxial feed terminals are translated into two orthogonal linear polarizations.
• the two orthogonal linear polarizations are offset 90 degrees from each other. Depending on the orientation of the antenna, this can be horizontal and vertical polarization, two slant linear polarizations (oriented at ⁇ 45 degrees), or some other combination .
• the dimensions illustrated are for a single sub-band coaxial cavity antenna operating in a frequency range from 2.50 GHz to 4.50 GHz.
• the dimensions are illustrated in FIGURE 9 and explained in Table 1.
• Tables 5, 6 and 7 are the dimensions of a two sub-band coaxial cavity antenna 110, as illustrated in FIGURE 2.
• the dimensions given in Tables 5, 6 and 7 are for a two sub-band antenna operating in a frequency range of 0.50 GHz to 2.00 GHz, with the lower sub-band operating in a frequency range of 0.50 GHz to 1.00 GHz and the upper sub-band operating in a frequency range of 1.00 GHz to 2.00 GHz.
• FIGURES 9, 10A and 10B and Table 1 for illustrating the relationship between the dimensions of Tables 5, 6 and 7 and the two sub-band coaxial cavity antenna 110 of FIGURE 2.
• Width 0.2500
• the coaxial cavity antenna 410 of FIGURE 11 includes an elliptical-shaped inner conductor 412 and a similar elliptical-shaped outer conductor 414.
• the shaped coaxial cavity antenna 410 of FIGURE 11 includes the circumferentially distributed aperture teeth as described with reference to FIGURE 1 and also the aperture blocks or septums (also shown in FIGURE 1.)
• Also included in the shaped coaxial cavity antenna 410 are the cable supports 32 as illustrated in FIGURES 5 and 7.
• multi-band coaxial cavity antennas such as illustrated in FIGURES 2 and 3 may have elliptically-shaped inner conductors and outer conductors to propagate a shaped electromagnetic wave .
• FIGURE 12 there is shown an embodiment of the invention incorporating coaxial cavity antennas in a vertical array. As illustrated, a single sub-band coaxial cavity antenna 510 is vertically positioned with reference to a single sub-band coaxial cavity antenna 512. A vertical array of the coaxial cavity antennas of the present invention provide increased directivity (gain) by narrowing the elevation beam width.
• FIGURES 13 and 14 there is illustrated a line array of coaxial cavity antennas in accordance with the present invention.
• the antennas of FIGURES 13 and 14 are illustrated as reflector feeds, this is given by way of example only and not by way of limitation.
• the line array includes a horizontal line of received coaxial cavity antennas 610 and a horizontal line of transmit coaxial cavity antennas 612.
• the line array of antennas 610 and 612 are mounted to a support 614 and spaced from a reflector 616.
• the wideband coaxial antennas of the present invention can also be arrayed and implemented as a feed for reflector antennas as illustrated in FIGURES 13 and 14 in addition to use as individual antenna elements.
• Coaxial antennas incorporating the teachings of the present invention exhibit flat phase response over a wide frequency range and a minimum of 120 degrees, centered about zenith, in field of view. This response is in addition to a flat amplitude response. This allows the antenna to be used as a wideband and ultra-wideband antenna for the reception and transmission of extremely fast pulses.
• the coaxial antenna of the present invention when used as a reflector of the cassegrain, gregorian, corner, parabolic, or cylindrical type exhibits high gain across the full band of operation.
• the antennas of the present invention are also useful as a feed for any type of reflector. However, for cylindrical applications, the antennas are placed in a line feed array and scanned electronically in the non-varying plane of the reflector. Offset line arrays are placed next to the primary banded line array resulting in the reflector antenna useful over multiple bands of operation in the same aperture area.

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Waveguide Aerials (AREA)
• Aerials With Secondary Devices (AREA)
• Variable-Direction Aerials And Aerial Arrays (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Citations (6)

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• 1999
  • 1999-10-15 JP JP2000577734A patent/JP4428864B2/ja not_active Expired - Fee Related
  • 1999-10-15 AU AU12078/00A patent/AU1207800A/en not_active Abandoned
  • 1999-10-15 CN CNB998147753A patent/CN1211884C/zh not_active Expired - Fee Related
  • 1999-10-15 EP EP99970795A patent/EP1127383A1/en not_active Withdrawn
  • 1999-10-15 WO PCT/US1999/024184 patent/WO2000024084A1/en not_active Ceased
  • 1999-10-15 CA CA002347013A patent/CA2347013C/en not_active Expired - Fee Related
  • 1999-10-15 US US09/418,764 patent/US6356241B1/en not_active Expired - Lifetime

Patent Citations (7)

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