Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
  • H01Q15/14—Reflecting surfaces; Equivalent structures
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/42—Housings not intimately mechanically associated with radiating elements, e.g. radome
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
  • H01Q15/14—Reflecting surfaces; Equivalent structures
  • H01Q15/16—Reflecting surfaces; Equivalent structures curved in two dimensions, e.g. paraboloidal
• • 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

Definitions

• This invention relates to microwave reflector antennas. More particularly, the invention relates to a reflector antenna with a radome and reflector dish interconnection band clamp which enhances signal pattern and mechanical interconnection characteristics.
• the open end of a reflector antenna is typically enclosed by a radome coupled to the distal end of the reflector dish.
• the radome provides environmental protection and improves wind load characteristics of the antenna.
• Edges and/or channel paths of the reflector dish, radome and/or interconnection hardware may diffract or enable spill-over of signal energy present in these areas, introducing undesirable backlobes into the reflector antenna signal pattern quantified as the front to back ratio (F/B) of the antenna.
• the F/B is regulated by international standards, and is specified by for example, the FCC in 47 CFR Ch.1 Part 101 .1 15 in the United States, by ETSI in EN302217-4-1 and EN302217-4-12 in Europe, and by ACMA RALI FX 3 Appendix 1 1 in Australia.
• Prior antenna signal pattern backlobe suppression techniques include adding a backlobe suppression ring to the radome, for example via metalizing of the radome periphery as disclosed in commonly owned US Utility Patent No. 7,138,958, titled "Reflector Antenna Radome with Backlobe Suppressor Ring and Method of
• the required metalizing operations may increase manufacturing complexity and/or cost, including elaborate coupling arrangements configured to securely retain the shroud upon the reflector dish without presenting undesired reflection edges, signal leakage paths and/or extending the overall size of the radome.
• the thin metalized ring layer applied to the periphery of the radome may be fragile, requiring increased care to avoid damage during delivery and/or installation.
• Reflectors employing castellated edge geometries to generate constructive interference of the edge diffraction components have also been shown to improve the F/B, for example as disclosed in commonly owned Canada Patent No. CA887303 "Backlobe Reduction in Reflector-Type Antennas" by Holtum et al.
• Such arrangements increase the overall diameter of the antenna, which may complicate radome attachment, packaging and installation.
• the addition of a shroud to a reflector antenna improves the signal pattern generally as a function of the shroud length, but also similarly introduces significant costs as the increasing length of the shroud also increases wind loading of the reflector antenna, requiring a corresponding increase in the antenna and antenna support structure strength.
• an interconnection between the shroud and a radome may introduce significant F/B degradation.
• a conventional band clamp 1 applied to retain a radome 3 upon the reflector dish 7 or shroud may introduce diffraction edges and/or signal leakage paths, for example as shown in Figure 1 .
• Metal taping, RF gaskets or the like may be applied to reduce F/B degradation resulting from band clamp use.
• these materials and procedures increase manufacturing costs and/or installation complexity and may be of limited long- term reliability.
• Figure 1 is a schematic enlarged cut-away side view of a conventional prior art band clamp radome and reflector dish interconnection, demonstrating an RF signal leakage path.
• Figure 2 is a schematic isometric cut-away view of a reflector antenna with radome to reflector dish band clamp interconnection.
• Figure 3 is a schematic partial cut-away side view of a radome to reflector dish band clamp interconnection.
• Figure 4 is an enlarged cut-away side view of a first exemplary radome to reflector dish band clamp interconnection.
• Figure 5 is a graph illustrating a range of exemplary band clamp distal lip inner diameter to reflector dish aperture ratios and their effect upon corresponding reflector antenna F/B over a range of operating frequencies.
• Figure 6 is a graph illustrating a range of band clamp widths and their effect upon corresponding reflector antenna F/B.
• Figure 7 is a graph comparing measured co-polar F/B performance related to RF signal leakage between conventional band clamp and presently disclosed "new" band clamp configurations.
• Figure 8 is a graph comparing measured cross-polar F/B performance related to RF signal leakage between conventional band clamp and presently disclosed "new" band clamp configurations.
• Figure 9 is a graph of measured co-polar radiation patterns of a 0.6m reflector antenna with a bandclamp with a 1 .1 wavelength width.
• Figure 10 is a graph of measured cross-polar radiation patterns of a 0.6m reflector antenna with a bandclamp with a 1 .1 wavelength width.
• Figure 1 1 is an enlarged cut-away side view of a second exemplary radome to reflector dish band clamp interconnection.
• Figure 12 is an enlarged cut-away side view of a third exemplary radome to reflector dish band clamp interconnection, including a width ring.
• Figure 13 is a graph comparing predicted F/B enhancement with a band clamp of width of 0.5 and 1 .2 wavelengths.
• Figure 14 is a graph of measured co-polar radiation patterns for a reflector antenna with a band clamp with a 0.5 wavelength width.
• Figure 15 is a graph of measured cross-polar radiation patterns for a reflector antenna with a band clamp with a 0.5 wavelength width.
• Figure 16 is a graph of measured co-polar radiation patterns for a reflector antenna with a band clamp with a 1 .2 wavelength width.
• Figure 17 is a graph of measured cross-polar radiation patterns for a reflector antenna with a band clamp with a 1 .2 wavelength width.
• Figure 18 is an enlarged cut-away side view of a third exemplary radome to reflector dish band clamp interconnection, including a width ring with radial outward bend.
• Figure 19 is a graph comparing predicted F/B enhancement with a band clamp with a width ring configuration of between 0 and 60 degrees radial outward bend.
• a band clamp 1 is generally operative to retain a radome 3 upon the open distal end 5 of a reflector dish 7, creating an environmental seal that protects the reflector dish 7, subref lector 9 and/or feed 1 1 of a reflector antenna 13 from environmental fouling.
• the band clamp 1 is provided with inward facing distal and proximal lips 15, 17.
• a turnback region 19 of the proximal lip 17 is dimensioned to engage the outer surface 21 of the signal area 23 of the reflector dish 7. The turnback region 19 may be applied, for example, as an outward bend prior to the inward end 25 of the proximal lip 17.
• the diameter of the band clamp 1 is progressively reduced, driving the turnback region 19 against the convex outer surface 21 of the signal area 23 of the reflector dish 7, into a uniform circumferential interference fit.
• the turnback region 19 slides progressively inward along the outer surface 21 of the signal area 23 of the reflector dish 7 toward the reflector dish proximal end 27.
• the distal lip 15 of the band clamp 1 also moves towards the reflector dish proximal end 27, securely clamping the radome 3 against the distal end 5 of the reflector dish 7. Because the interference fit between the turnback region 19 and the outer surface 21 of the reflector dish 7 is circumferentially uniform, any RF leakage between these surfaces is reduced.
• the radome 3 may be provided with a greater diameter than the reflector dish 7, an annular lip 29 of the radome 3 periphery mating with an outer diameter of the distal end 5 of the reflector dish 7, keying the radome 3 coaxial with the reflector dish 7 and providing surface area for spacing the band clamp 1 from the signal area 23 of the reflector dish 7.
• the flanges may be dimensioned and the band clamp 1 similarly dimensioned such that the distal lip 15 of the band clamp 1 is even with or extends slightly inward of a reflector aperture H, defined as the largest diameter of the reflector dish 7 surface upon which signal energy is distributed by the subreflector 9, to form a band clamp inner diameter D.
• a reflector aperture H defined as the largest diameter of the reflector dish 7 surface upon which signal energy is distributed by the subreflector 9, to form a band clamp inner diameter D.
• the band clamp inner diameter D may be dimensioned with respect to reflector aperture H, resulting in significant F/B enhancement as illustrated in Figure 5.
• a D/H ratio of 0.97- 1 .0 may be applied.
• band clamp 1 width "A" determines the distance between band clamp 1 outer corner(s) 31 acting as diffraction/scatter surfaces.
• normalized F/B is improved when the width "A" is between 0.8 and 1 .5 wavelengths of the operating frequency, which can be operative to generate mutual interference of surface currents traveling along the band clamp 1 outer periphery and/or scatter interference.
• Figures 7 and 8 The significant improvement in measured F/B performance in a 0.6 meter reflector antenna configurations for both co-polar and cross-polar responses with a conventional prior art band clamp 1 and the "new" presently disclosed band clamp 1 configuration are illustrated in Figures 7 and 8.
• Figures 9 and 10 illustrate measured backlobe levels of co-polar and cross-polar radiation patterns in the 26 GHz band within the regulatory envelopes at greater than 71 dB with the Figure 4 band clamp 1 configuration, in which the width "A" is equal to 1 .1 wavelengths.
• width "A” may be difficult to achieve for some operating frequencies without incorporating further structure in the radome and/or reflector dish periphery.
• the width "A” may be increased via the application of a fold 33 in the band clamp from the desired extent of the width "A” back toward the reflector dish 7.
• the pictured embodiment is simplified for demonstration purposes with respect to extending the width "A” but may similarly be applied with a fold 33 and proximal lip 17 that extends further inward and includes a turnback region 19 contacting the outer surface 21 of the signal area 23 of the reflector dish 7.
• an extension of the width "A" may be cost effectively achieved by attaching a further width ring 35 of metallic and/or metal coated material to the band clamp 1 outer diameter.
• the width ring 35 may be applied with any desired width, cost effectively securely attached by spot welding or fasteners such as screws, rivets or the like.
• Figure 13 illustrates 18 GHz band RF modeling software predictions of F/B
• the width ring 35 may be provided in an angled configuration as demonstrated in Figure 18. As shown in Figure 19, RF modeling software predictions of F/B improvement indicate progressively increasing improvement as the angle applied increases from zero (flat width ring 35 cross section) to sixty degrees of diffraction gradient.
• the disclosed band clamp 1 can enable significant manufacturing, delivery, installation and/or maintenance efficiencies. Because the band clamp 1 enables simplified radome 3 and reflector dish 7 periphery geometries, the resulting reflector antenna 13 may have improved materials and manufacturing costs. Because the band clamp 1 is simply and securely attached, installation and maintenance may be simplified compared to prior reflector antenna 13 configurations with complex peripheral geometries, delicate back lobe suppression ring coatings, platings and/or RF absorbing materials. Because the band clamp 1 may be compact and applied close to the reflector antenna aperture H, the overall diameter of the reflector antenna 13 may be reduced, which can reduce the reflector antenna 13 wind loading characteristics and the required packaging dimensions.

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Aerials With Secondary Devices (AREA)
• Details Of Aerials (AREA)

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• 2009
  • 2009-12-11 US US12/636,068 patent/US8259028B2/en active Active
• 2010
  • 2010-09-15 CN CN201080056187.7A patent/CN102714343B/zh active Active
  • 2010-09-15 WO PCT/IB2010/054173 patent/WO2011070451A2/en active Application Filing
  • 2010-09-15 EP EP10835569.4A patent/EP2510576B1/en active Active
  • 2010-09-15 BR BR112012013654-2A patent/BR112012013654B1/pt active IP Right Grant

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