EP0196734A2 - Cassegrain-Antenne für Fernsehempfang - Google Patents

Cassegrain-Antenne für Fernsehempfang Download PDF

Info

Publication number
EP0196734A2
EP0196734A2 EP86300149A EP86300149A EP0196734A2 EP 0196734 A2 EP0196734 A2 EP 0196734A2 EP 86300149 A EP86300149 A EP 86300149A EP 86300149 A EP86300149 A EP 86300149A EP 0196734 A2 EP0196734 A2 EP 0196734A2
Authority
EP
European Patent Office
Prior art keywords
horn
antenna
subreflector
main reflector
superstructure
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.)
Withdrawn
Application number
EP86300149A
Other languages
English (en)
French (fr)
Other versions
EP0196734A3 (de
Inventor
James N. Rothbarth
Edward W. Smith
Yahya Rahmat-Samii
William Anthony Imbriale
Victor Galindo
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.)
Satellite Technology Services Inc
Original Assignee
Satellite Technology Services 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 Satellite Technology Services Inc filed Critical Satellite Technology Services Inc
Publication of EP0196734A2 publication Critical patent/EP0196734A2/de
Publication of EP0196734A3 publication Critical patent/EP0196734A3/de
Withdrawn legal-status Critical Current

Links

Images

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
    • H01Q15/141—Apparatus or processes specially adapted for manufacturing reflecting surfaces
    • H01Q15/142—Apparatus or processes specially adapted for manufacturing reflecting surfaces using insulating material for supporting the reflecting surface
    • 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

Definitions

  • This invention relates to an antenna of the Cassegrain type, and utilizes the near field focal point of the subreflector to represent the phase and amplitude origin for shaping the main reflector and subreflector.
  • the invention further utilizes a corrugated, profiled horn, the wall.of which is generally S-shaped in longitudinal cross section, and both the main reflector and subreflector are "shaped" in accordance with the horn pattern to optimize the energy distribution over the aperture of the main reflector to provide a high gain, high efficiency antenna.
  • the antenna of the present invention is particularly designed as a television receive only (TVRO) antenna and more specifically for use as a C-band antenna, although many of its design characteristics can be used with other antennas, for other uses, and at other frequency. bands such as, for example, Ku-band.
  • Cassegrain antennas are widely known for military and commercial use, but heretofore the advanced engineering techniques and extraordinarily expensive design methods inherently required to produce an efficient Cassegrain antenna have made such antennas impractical for TVRO use.
  • This invention has succeeded in employing such techniques and methods while providing a highly efficient true Cassegrain antenna that can be mass produced and sold at a reasonable price, thus making it practical as a TVRO antenna, or otherwise as a transmitting or receiving antenna.
  • the antenna of this invention is a true Cassegrain. It includes a main reflector, subreflector, and horn.
  • the horn is aimed toward the subreflector such that energy through the aperture of the main reflector is directed to the subreflector and then to the horn.
  • the main reflector, subreflector, and horn are symmetrically oriented about the antenna axis (circularly symmetric), with the near field focal point of the feed lying on the axis.
  • the invention utilizes a corrugated, profiled horn where the wall of the horn in longitudinal cross section is generally S-shaped.
  • the corrugations and shaping provide substantially equal E and H plane feed patterns. over a broad band width at a low VSWR, low cross-polarization, and a good spherical phase pattern down to a low energy level.
  • the antenna is a near field design with the near field focal point of the feed deep within the horn.
  • the antenna is "dual shaped" such that the subreflector and main reflector are shaped in accordance with the horn pattern to provide substantially uniform energy distribution and high efficiency.
  • the near field design and profiled horn allow use of a much smaller subreflector placed substantially closer to the main reflector than is otherwise possible.
  • the antenna of this invention utilizes a large F/D ratio, preferably in excess of .5, to provide low crossed-polarization and economy of labor and materials in making the main reflector.
  • the subreflector and main reflector are shaped to provide nulls in the radiation pattern in accordance with satellite spacings every two degrees.
  • Major portions of the antenna are uniquely constructed of molded plastic to greatly reduce the cost. These portions include the horn, and the superstructure of the main reflector, and may also include the subreflector.
  • the antenna of this invention is preferably a C-band TVRO Cassegrain antenna, in a broader sense many of the same design characteristics may be used to varying degrees with other types of antennas, for other uses, and for other frequency bands.
  • the antenna generally includes a main reflector 12, a subreflector 14, and a horn 16, all of which are circularly symmetric.
  • the main reflector 12 includes a superstructure 18 with a mesh covering 20 on the reflective side thereof ( Figures 3 and 4).
  • the superstructure 18 is of a honeycomb configuration having a large number of openings 22 of hexagonal shape.
  • the main reflector has a central panel 24 symmetric about its center, and a multiple of generally triangular panels or petals 26 extending radially from the central panel.
  • the petals 26 are identical and are attached at their inner ends at the periphery of the central panel 24. Each petal is also attached at its side edges to the side edges of adjacent petals.
  • the central panel and each of the petals is double curved such that when assembled there is provided a smoothly shaped superstructure with a hexagonal perimeter as shown in Figure 1.
  • extender panels which may be either of the configuration shown at 30 or the configuration shown at 32 of Figure 8.
  • the extender panels effectively increase the aperture of the main reflector and are also of a honeycomb configuration as with the central panel and petals.
  • the extender panels are attached at the perimeter of the petals, and depending on the configuration of the extender panels used, the resultant main reflector may have a circular perimeter (extender panels 30) or a hexagonal perimeter (extender panels 32).
  • the main panel, petals, and extender panels are all formed of plastic by injection molding.
  • the subreflector may be changed to optimize the increased aperture of the main reflector, and is positioned a nominal two inches (5.08 cm) further away from the main reflector. Even with the same subreflector, the antenna's performance is improved as the extender panels act as noise shields.
  • the mesh covering 20 is of die-cut aluminum, flattened, and powdered coated and with a weather protective coating of polyester.
  • the mesh covering is attached to the superstructure by suitable fasteners 34.
  • the mesh may be of molded plastic and plated with copper and nickel to provide the reflective surface.
  • each spar has a round portion 38 and an outer flattened portion 40.
  • the subreflector 14 may be of one piece plastic molded construction having a smoothly shaped reflective surface 42 facing the main reflector with reinforcing ribs 44 at the side of the subreflector opposite the reflective surface.
  • the central portion of the subreflector functions as a vertex plate for low VSWR and minimum blockage effect by the subreflector.
  • the vertex plate is an integral part of the subreflector so that optically no energy is wasted by unnecessary scattering from the subreflector.
  • the subreflector includes cap portions 46 that fit over the ends of the spars and are attached thereto for mounting the subreflector at the outer end of the spars and spaced away from the main reflector.
  • the spars may be of aluminum. Alternately, the subreflector may have a circular perimeter, rather than hexagon as shown, and may be of spun or stamped aluminum with a protective coating.
  • the horn 16 extends through the center of the central panel 24 of the superstructure toward the subreflector with the mouth of the horn facing the reflective surface 42 of the subreflector.
  • the horn is a corrugated, profiled horn. It has a throat portion 50 and a mouth portion 52 of larger diameter than the throat, each of which are of a stove pipe or generally straight configuration. Between the throat and mouth portions is a curved intermediate portion 54. The transitions between the throat, intermediate, and mouth portions, are smooth such that the shape of the horn wall viewed in longitudinal cross section as in Figure 4 is generally S-shaped.
  • the horn is circularly symmetric about its longitudinal axis and is corrugated as shown substantially along its entire length.
  • the horn has equilaterally spaced radial webs 60 extending outwardly from the horn wall to the spars 36. Also near the throat and mouth of the horn are horizontal webs 61 and ring clamps 62 and 63 that clamp onto the spars to support the horn.
  • the horn also includes rearwardly extending flanges 64 for connecting the horn to the central panel 24 of the superstructure with fasteners 65. Slots 66 allow axial adjustment of the horn.
  • each section includes a wall portion 67 representing one-third of the horn wall; two radial web portions 68 each representing half a web 60; horizontal web portions 69 representing one-third of the horizontal webs 61; half ring portions 70 and 71 at the outer edge of each radial web portion and representing half the ring clamps 62 and 63, respectively; half flange portions 72 each representing half a flange 64; and ears 74 each representing half a wing clamp 56.
  • Each horn section, including the wall portion, half web portions, half ring portions, half flange portions, and ears, is of one piece molded construction. The three sections are joined, such as by solvent welding, to form the horn.
  • the inner surface of the horn and reflective surface 42 of the subreflector are of an electromagnetic conductive material which may comprise a first coating of copper and an outer coating of nickel. These coatings may be forty-millionths and ten-millionths, respectively.
  • the horn and subreflector are then both painted with a weather protective coating such as polyurethane.
  • the horn also includes a weather cap 78 of an electromagnetic energy transparent material.
  • the main reflector, subreflector, and horn are supported by a spider 80 secured to the nonreflective side of the main reflector.
  • the spider has a central portion 82 with a hexagonal opening therein, and radial arms 84 extending outwardly therefrom.
  • the spider has a shape that conforms to that of the superstructure.
  • the superstructure is mounted to the spider by means of fasteners 86 which extend through holes in the spider and holes 88 in the central panel 24 and holes 90 in the petals 26.
  • the spars 36 extend through openings 91 in the spider.
  • the spider has portions 92 with arcuate surfaces 94 to define a track for declination adjustment.
  • a generally U-shaped connector 100 is located rearwardly of the spider and has a pivot pin 102 extending therethrough. Mounted on the pivot pin outwardly of each end of the U-connector is a spider pad 104. These spider pads have arcuate surfaces 106 that mate with the arcuate surfaces 94.
  • an azimuth drive assembly 110 including a worm drive and housing 112, the housing of which captures the U-connector 100, and an annular gear track 114 surrounding the U-connector with the ends of the track mounted at 116 to the central portion of the spider.
  • the combination of the annular track and worm drive housing hold the U-connector and spider pads in place so that the arcuate surfaces 106 of the spider pads engage the arcuate surfaces 94 of the spider.
  • a pivot yoke 120 is mounted at the upper end of a mast 122 with the top of the yoke pivotally mounted at 124 near the bottom of the U-connector and rearwardly of the pivot pin 102.
  • a threaded rod 126 extends through a sleeve 128 pivotally mounted at the bottom of the pin 102 with the end of the threaded rod pivotally connected near the lower end of the yoke.
  • Suitable adjusting nuts 130 allow adjustment of the threaded rod to provide an elevation adjust for the antenna.
  • Azimuth adjust is provided by the drive 110 which pivots the spider and all the components mounted thereto, as well as the spider pads, about the axis of the pin 102. Declination adjustment is provided by positioning the spider relative to the spider pads along the arcuate surfaces.
  • the horn is held in a selected axial position by the fasteners 65, and the subreflector is held in a selected axial position by the fact that it is mounted to the spars 36 which in turn are held in a fixed axial position by the horn which is clamped to the spars.
  • the horn and subreflector may each be axially adjusted independently of the other.
  • the subreflector may.be positioned by loosening the clamps 62 and 63 and sliding the spars in or out as desired of the openings 38 and 91 in the superstructure and spider.
  • FIG. 9 is a schematic diagram showing the geometry of the Cassegrain antenna 10 where:
  • Appendix A attached hereto as Appendix A are the Xl, Y coordinates for the shaping of the main reflector including the extender panels; attached hereto as Appendix B are the X2, Y coordinates for the shaping of the subreflector, one set for a 43 inch (109.22 cm) radius optical edge, and another set for a 44 inch (111.76 cm) radius optical edge; and attached hereto as Appendix C are inside and outside radii versus Y axis coordinate for the shaping of the horn.
  • the overall length of the horn is 28.4 inches (72.136 cm).
  • Figure 10 shows computed principal polarization and cross-polarization radiation patterns taken at forty-five degrees where the maximum cross-polarization occurs, making an allowance for wind loading at 20 mph. From the patterns it can be seen that the gain of the antenna at zero degrees at center band, f - 3.95 GHz, is approximately 39 DB. Nulls between the main and side lobes occur substantially at two degree intervals as shown.
  • the Cassegrain antenna of the present invention is particularly adapted for mass production to provide a low cost antenna. While it is designed primarily as a TVRO antenna, and more particularly as a C-band antenna, certainly its unique design features offer significant advantages for other uses and at other frequency bands including Ku-band.
  • the main reflector, subreflector, and horn are all circularly symmetric.
  • the antenna utilizes a near field design such that the near field focal point is deep within the horn, the near field focal point representing the phase and amplitude origin for shaping the main reflector and subreflector.
  • Both the main reflector and subreflector are shaped in the sense that the main reflector is not a true parabola and the subreflector is not a true hyperbola.
  • the antenna is "dual shaped" in that both the main reflector and subreflector are shaped in accordance with the horn pattern to optimize the energy distribution over the aperture of the main reflector for high efficiency.
  • the corrugations and shaping of the horn provide substantially equal E and H plane feed patterns over a broad bandwidth at a low VSWR, and allows for a com- pact design placing the near field focal point, and hence the subreflector, closer to the main reflector.
  • the near field design itself allows use of a much smaller subreflector placed substantially closer to the main reflector than is otherwise possible where the far field focal point is used.
  • the horn configuration also has low cross-polarization, and a good spherical phase pattern down to a low energy level.
  • the invention utilizes a large F/D ratio, for example, .55, and preferably in excess of .5, to provide low cross-polarization and economy of labor and materials in making the main reflector.
  • the subreflector and main reflector are shaped to provide nulls in the radiation pattern at -4°, -2°, 2° and 4° to coincide with satellite spacing.
  • the effective aperture of the antenna can be increased. While it has been known to provide extender panels for a parabolic reflector, to do so created amplitude and phase error that moving the feed would not completely correct. With the dual shaped Casse- grain design of the present invention, the extender panels are also properly shaped, and any phase and amplitude distortion created by the addition of the panels is corrected merely by adjusting the location and shape of the subreflector. Thus, with the present invention the effective aperture of the antenna can be increased with the addition of the extender panels and a relatively simple and inexpensive replacement and adjustment of the subreflector.
  • the performance of the antenna can be optimized by changing the subreflector and moving it when the the extender panels are mounted to the main reflector, it is not necessarily required to change the subreflector to realize an increased performance.
  • the extender panels When the extender panels are added to increase the size of the main reflector dish, they effectively increase the noise shielding if the subreflector is not changed. This lowers the background noise, or T in a G/T gain-to-noise ratio, so that an improved performance is realized.
  • the gain portion of the antenna is only minimally improved, there is no substantial change in the null spacings of the main reflector antenna design.
  • the extender panels may be utilized either with a different subreflector, or even without a different subreflector to improve the performance of the base antenna.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Aerials With Secondary Devices (AREA)
  • Waveguide Aerials (AREA)
EP86300149A 1985-03-28 1986-01-10 Cassegrain-Antenne für Fernsehempfang Withdrawn EP0196734A3 (de)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US71751485A 1985-03-28 1985-03-28
US717514 1985-03-28
US74024185A 1985-05-31 1985-05-31
US740241 1991-08-05

Publications (2)

Publication Number Publication Date
EP0196734A2 true EP0196734A2 (de) 1986-10-08
EP0196734A3 EP0196734A3 (de) 1988-08-03

Family

ID=27109719

Family Applications (1)

Application Number Title Priority Date Filing Date
EP86300149A Withdrawn EP0196734A3 (de) 1985-03-28 1986-01-10 Cassegrain-Antenne für Fernsehempfang

Country Status (2)

Country Link
EP (1) EP0196734A3 (de)
AU (1) AU5241886A (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2231445A (en) * 1989-04-18 1990-11-14 Anthony Edgar Sale Aerial system
EP1825567A1 (de) * 2004-08-12 2007-08-29 The Boeing Company Verfahren und vorrichtung zur montage einer drehreflektorantenne zur minimierung des schwenkwinkels

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2240893A1 (de) * 1972-08-19 1974-03-07 Gruenzweig & Hartmann Spiegelantenne, insbesondere fuer das 12 ghz-band
US3897294A (en) * 1974-05-06 1975-07-29 Gen Dynamics Corp Method of forming a parabolic antenna
DE2551545A1 (de) * 1975-11-17 1977-05-26 Siemens Ag Drehsymmetrische cassegrain-antenne
JPS55147005A (en) * 1979-05-04 1980-11-15 Mitsubishi Electric Corp Corrugated cone horn
EP0105007A1 (de) * 1982-09-28 1984-04-04 Thomson-Csf Verfahren zur Herstellung eines Kunststoffreflektors und nach dem Verfahren hergestellter Reflektor
EP0108515A1 (de) * 1982-10-11 1984-05-16 Cambridge Electronic Industries plc Parabolspiegelantenne

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2240893A1 (de) * 1972-08-19 1974-03-07 Gruenzweig & Hartmann Spiegelantenne, insbesondere fuer das 12 ghz-band
US3897294A (en) * 1974-05-06 1975-07-29 Gen Dynamics Corp Method of forming a parabolic antenna
DE2551545A1 (de) * 1975-11-17 1977-05-26 Siemens Ag Drehsymmetrische cassegrain-antenne
JPS55147005A (en) * 1979-05-04 1980-11-15 Mitsubishi Electric Corp Corrugated cone horn
EP0105007A1 (de) * 1982-09-28 1984-04-04 Thomson-Csf Verfahren zur Herstellung eines Kunststoffreflektors und nach dem Verfahren hergestellter Reflektor
EP0108515A1 (de) * 1982-10-11 1984-05-16 Cambridge Electronic Industries plc Parabolspiegelantenne

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, vol. 5, no. 19 (E-44)[691], 4th February 1981; & JP-A-55 147 005 (MITSUBISHI DENKI K.K.) 15-11-1980 *
ZEITSCHRIFT F]R FLUGWISSENSCHAFTEN UND WELTRAUMFORSCHUNG, vol. 4, no. 5, September/October 1980, pages 255-267, Köln, DE; W. SCH[FER: "Stand der Technik auf dem Gebiet grösserer entfaltbarer Parabolantennen-Strukturen für Raumfluggeräte" *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2231445A (en) * 1989-04-18 1990-11-14 Anthony Edgar Sale Aerial system
EP1825567A1 (de) * 2004-08-12 2007-08-29 The Boeing Company Verfahren und vorrichtung zur montage einer drehreflektorantenne zur minimierung des schwenkwinkels

Also Published As

Publication number Publication date
AU5241886A (en) 1986-10-02
EP0196734A3 (de) 1988-08-03

Similar Documents

Publication Publication Date Title
US6919855B2 (en) Tuned perturbation cone feed for reflector antenna
US7626557B2 (en) Digital UHF/VHF antenna
US10756422B2 (en) Antenna isolation shrouds and reflectors
US4788554A (en) Plated plastic injection molded horn for antenna
US4673945A (en) Backfire antenna feeding
US7737903B1 (en) Stepped-reflector antenna for satellite communication payloads
US20080094298A1 (en) Antenna with Shaped Asymmetric Main Reflector and Subreflector with Asymmetric Waveguide Feed
US6844862B1 (en) Wide angle paraconic reflector antenna
EP2577802A1 (de) Segmentierter antennenreflektor mit abschirmung
US4876554A (en) Pillbox antenna and antenna assembly
WO1989006446A1 (en) Multimode dielectric-loaded multi-flare antenna
JPH10276004A (ja) アンテナを電気的にダウンティルトする連続可変位相シフタ
US6331839B1 (en) Satellite antenna enhancer and method and system for using an existing satellite dish for aiming replacement dish
CA1205556A (en) Grid antenna
EP0196734A2 (de) Cassegrain-Antenne für Fernsehempfang
US4423422A (en) Diagonal-conical horn-reflector antenna
US4710777A (en) Dish antenna structure
TWI715284B (zh) 天線組件
AU2020204437A1 (en) Wide Band Log Periodic Reflector Antenna for Cellular and Wifi
CA2604405A1 (en) Digital uhf/vhf antenna
US5191350A (en) Low wind load parabolic antenna
US6215453B1 (en) Satellite antenna enhancer and method and system for using an existing satellite dish for aiming replacement dish
US4636801A (en) Multiple reflector system with dielectric support webs and foam body
US5999143A (en) Antenna system parabolic reflector, flat plate shroud and radome
CN86211074U (zh) 多焦距抛物面平板形卫星地面站天线

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

PUAL Search report despatched

Free format text: ORIGINAL CODE: 0009013

AK Designated contracting states

Kind code of ref document: A3

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19880801

RIN1 Information on inventor provided before grant (corrected)

Inventor name: RAHMAT-SAMII, YAHYA

Inventor name: GALINDO, VICTOR

Inventor name: IMBRIALE, WILLIAM ANTHONY

Inventor name: SMITH, EDWARD W.

Inventor name: ROTHBARTH, JAMES N.