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US3587098A - Lightweight reflecting material for radar antennas - Google Patents

Lightweight reflecting material for radar antennas Download PDF

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Publication number
US3587098A
US3587098A US766888A US3587098DA US3587098A US 3587098 A US3587098 A US 3587098A US 766888 A US766888 A US 766888A US 3587098D A US3587098D A US 3587098DA US 3587098 A US3587098 A US 3587098A
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laminate
radio frequency
set forth
dacron
frequency reflective
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US766888A
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Charles N Gosnell
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US Department of Navy
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US Department of Navy
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    • 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

Definitions

  • the present invention relates to the structure of fabric used in an inflatable antenna, and more particularly relates to a laminated fabric which is used in constructing the parabolic reflector of an inflatable antenna.
  • the best prior art material was a glass cloth, coated with silver powder and covered with a vinyl facing.
  • the glass cloth is heavy, and the final composite weighed 15 to 17 ounces per square yard.
  • glass yarns are adversely sensitive to folding, so a stronger and heavier cloth was required to compensate for weakening of the fabric due to bending.
  • the general purpose of this invention is to provide an RF. reflective material for an antenna which is lightweight, resists weakening due to folding, has a low tendency to elongate under the loads imposed on it, is very flexible, has excellent reflectivity, even after severe handling and folding, and has good tear and rip resistance.
  • the present invention provides a laminated fabric, the typical construction of which is organic film-metallic film-woven material-metalic film-organic film.
  • FIG. ll illustrates a diagrammatic view of the laminate structure of the fabric
  • FIG. 2 shows a diagrammatic view of a modification of the invention.
  • FIG. 3 illustrates the structure of FIG. 2 in a parabolic reflector.
  • FIG. 4 is a side view of FIG. 3.
  • an important factor to be considered is the strength to weight ratio of the material. This ratio is a paramount consideration since the major reason for the existence of an inflatable antenna is its very light weight in comparison to an equivalent rigid antenna. Another important consideration is the dimensional stability of the material, since the material will .have sustained loads imposed on it due to the inflation of the antenna. A reasonable degree of elongation would be acceptable in a radome material because its dimensional requirements are not critical. However, a good lens material should have relatively low elongation since it is required to balance and position loads on the frame of the reflector.
  • the reflector material should have very low elongation at its design loading because a secondary type of elongation, known as creep, could introduce an uncontrolled dimensional change and cause the parabolic reflector to change its shape. This type of change could defocus the reflector and cause a marked degradation in antenna performance.
  • the selected material must also be flexible so the antenna may be folded for compact stowage prior to inflation, but the folding should not degrade either the strength or the reflectivity of the material.
  • the material should have a high resistance to both the initial starting of a tear and tear propagation, once the rip has been initiated.
  • a laminated fabric which has as its exterior coatings organic polyester films I2 and 20, which may be Mylar. Beneath each of the exterior coatings l2 and 20 are layers of aluminum foil 14 and 18, and sandwiched in between the aluminum foil layers 14 and 18 is a Dacron leno weave material 16.
  • the organic films l2 and 20 have good dimensional stability and a high strength to weight ratio. They also have high resistance to the initial starting of a tear, but once the tear is initiated, they have very low resistance to tear propagation.
  • the open weave material which in the preferred embodiment is a Dacron leno weave, rectifies this deficiency of the polyester films, and effectively resists tear propagation.
  • the addition of the open weave material has the additional advantage of allowing much thinner and lighter organic films to be used, since the material will carry a good portion of the loading due to inflation of the antenna.
  • Polyester fibers of Dacron were chosen as the yarn for the leno weave materials since they are not damaged by folding.
  • Aluminum foil was chosen as the reflective material because of its light weight.
  • Alternatives, such as a fine silver pigment in a polyester resin base, are undesirable because of their relatively heavy weight.
  • the preferred laminate is constructed in the following manner: 0.000] 8 inch aluminum film isjoined to 0.00035 inch Mylar to form a sublaminate. Two pieces of this sublaminate are then sandwiched around 0.6 ounce per square yard, 12X4 count, high tenacity Dacron leno weave, with the Mylar faces being on the outside of the finished laminate. The sublaminates are joined to the leno weave material by adhesive bonding, although thermal heat sealing or dielectric sealing might also be used.
  • the finished laminate is very light weight, at less than 3.6 ounces per square yard, and has a power reflectivity of greater than 97 percent.
  • the material for the radome and lens, which do not require R.F. reflectivity, was chosen to be a 12x4 count high tenacity Dacron leno weave laminated between two 0.25 mil Mylar films.
  • the wires 24 and 22 may be woven as if the Litz wires were conventional textile yarns, or may simply be laid together in a rectangular pattern without weaving. Dimensional stability is high since the wire carries most of the load imposed on the laminate, and the laminate is not adversely effected by folding since the fine strands which comprise each individual Litz wire bend easily without kinking.
  • FIG. 3 illustrates a front view of a parabolic reflector 30, while FIG. 4 illustrates a side view of the same reflector 30.
  • the reflector is composed of I2 gores of laminated material joined at seams 32.
  • One important construction feature to be noted is that one set of the Litz wires, either 22 or 24, must run in the direction of polarization of the radar beam being tracked.
  • a lightweight radio frequency reflective laminate for use in a collapsible antenna comprising:
  • said first and second polyester films providing the laminate with good dimensional stability and a high strength to weight ratio
  • Dacron Yarn material sandwiched between said first and second polyester film said Dacron material providing good dimensional stability, a high strength to weight ratio, and also resistance to tear propagation;
  • said first and second polyester films, said Dacron material and said aluminum reflective material all being joined together to form a unitary laminate.
  • a lightweight radio frequency reflective laminate as set forth in claim 1 wherein:
  • said open weave material has a leno weave.
  • said at least one layer ofradio frequency material comprises a thin layer of aluminum foil. 4.
  • a lightweight radio frequency reflective laminate as set forth in claim 3 wherein:
  • each of said first and second polyester films is comprised of Mylar. 5.
  • a lightweight radio frequency reflective laminate as set forth in claim 4 wherein:
  • said at least one layer of radio frequency reflective aluminum foil comprises two layers, each of which is sandwiched between said Dacron leno weave material and one of said layers of Mylar. 6.
  • a lightweight radio frequency reflective laminate as set forth in claim 5 wherein:
  • each of said layers of aluminum foil is 18 mils thick; each of said layers of Mylar is 35 mils thick; and
  • said laminate composes the reflector of a collapsible antenna.
  • a lightweight radio frequency reflective laminate as set forth in claim 1 wherein:
  • said at least one layer of radio frequency reflective material comprises two layers of material, each of which sandwiched between said open weave material and one of said layers of polyester film.
  • said laminate composes the reflector ofa collapsible anten-

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Aerials With Secondary Devices (AREA)

Abstract

A lightweight R.F. reflecting material for an inflatable antenna comprising a laminate of Mylar-aluminum foil-Dacron leno weavealuminum foil-Mylar.

Description

United States Patent Filed Inventor Appl. No.
Patented Assignee LIGHTWEIGHT REFLECTING MATERIAL FOR RADAR ANTENNAS -9 Claims, 4 Drawing Figs.
US. Cl 343/915 Int. Cl ..1-10lq 15/20 Field of Search 343/840, 872, 897, 915
References Cited UNITED STATES PATENTS Mcllroy et al. Price R0ttmayer.. Pessin Tipton Primary Examiner-Eli Lieberman Attorneys-R. S. Sciascia, T-. E. Hodges and W. F. McCarthy ABSTRACT: A lightweight R.F. reflecting material for an inflatable antenna comprising a laminate of Mylar-aluminum foil-Dacron leno weave-aluminum foil-Mylar.
POLYESTER FILM ALUMINUM FOIL ALUMINUM FOIL POLYESTER FILM DACRON LENO WEAVE MATERIAL PATENTEDJUHZZIHYI 3 5 7,09
POLYESTER FILM l4 ALUMINUM FOIL DACRON LENO WEAVE MATERIAL l8 ALUMINUM FOIL 2 POLYESTER FILM INVENTOR .F/G. 4. F7613.
CHARLES N. GOSNELL ATTORNEY LIGHTWEIGHT REF LECTING MATERIAL FOR RADAR ANTENNAS The present invention relates to the structure of fabric used in an inflatable antenna, and more particularly relates to a laminated fabric which is used in constructing the parabolic reflector of an inflatable antenna.
The best prior art material was a glass cloth, coated with silver powder and covered with a vinyl facing. However, the glass cloth is heavy, and the final composite weighed 15 to 17 ounces per square yard. Additionally, glass yarns are adversely sensitive to folding, so a stronger and heavier cloth was required to compensate for weakening of the fabric due to bending.
The general purpose of this invention is to provide an RF. reflective material for an antenna which is lightweight, resists weakening due to folding, has a low tendency to elongate under the loads imposed on it, is very flexible, has excellent reflectivity, even after severe handling and folding, and has good tear and rip resistance. To attain this, the present invention provides a laminated fabric, the typical construction of which is organic film-metallic film-woven material-metalic film-organic film.
The exact nature of this invention as well as other advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawings in which:
FIG. ll illustrates a diagrammatic view of the laminate structure of the fabric;
FIG. 2 shows a diagrammatic view of a modification of the invention.
FIG. 3 illustrates the structure of FIG. 2 in a parabolic reflector.
FIG. 4 is a side view of FIG. 3.
In the selection of a material for construction of an inflatable antenna, an important factor to be considered is the strength to weight ratio of the material. This ratio is a paramount consideration since the major reason for the existence of an inflatable antenna is its very light weight in comparison to an equivalent rigid antenna. Another important consideration is the dimensional stability of the material, since the material will .have sustained loads imposed on it due to the inflation of the antenna. A reasonable degree of elongation would be acceptable in a radome material because its dimensional requirements are not critical. However, a good lens material should have relatively low elongation since it is required to balance and position loads on the frame of the reflector. In addition, the reflector material should have very low elongation at its design loading because a secondary type of elongation, known as creep, could introduce an uncontrolled dimensional change and cause the parabolic reflector to change its shape. This type of change could defocus the reflector and cause a marked degradation in antenna performance. The selected material must also be flexible so the antenna may be folded for compact stowage prior to inflation, but the folding should not degrade either the strength or the reflectivity of the material. Additionally, the material should have a high resistance to both the initial starting of a tear and tear propagation, once the rip has been initiated.
Referring to FIG. 1 in which the preferred embodiment is illustrated, there is shown a laminated fabric which has as its exterior coatings organic polyester films I2 and 20, which may be Mylar. Beneath each of the exterior coatings l2 and 20 are layers of aluminum foil 14 and 18, and sandwiched in between the aluminum foil layers 14 and 18 is a Dacron leno weave material 16. The organic films l2 and 20 have good dimensional stability and a high strength to weight ratio. They also have high resistance to the initial starting of a tear, but once the tear is initiated, they have very low resistance to tear propagation. The open weave material, which in the preferred embodiment is a Dacron leno weave, rectifies this deficiency of the polyester films, and effectively resists tear propagation.
The addition of the open weave material has the additional advantage of allowing much thinner and lighter organic films to be used, since the material will carry a good portion of the loading due to inflation of the antenna. Polyester fibers of Dacron were chosen as the yarn for the leno weave materials since they are not damaged by folding. Aluminum foil was chosen as the reflective material because of its light weight. Alternatives, such as a fine silver pigment in a polyester resin base, are undesirable because of their relatively heavy weight.
The preferred laminate is constructed in the following manner: 0.000] 8 inch aluminum film isjoined to 0.00035 inch Mylar to form a sublaminate. Two pieces of this sublaminate are then sandwiched around 0.6 ounce per square yard, 12X4 count, high tenacity Dacron leno weave, with the Mylar faces being on the outside of the finished laminate. The sublaminates are joined to the leno weave material by adhesive bonding, although thermal heat sealing or dielectric sealing might also be used. The finished laminate is very light weight, at less than 3.6 ounces per square yard, and has a power reflectivity of greater than 97 percent.
The material for the radome and lens, which do not require R.F. reflectivity, was chosen to be a 12x4 count high tenacity Dacron leno weave laminated between two 0.25 mil Mylar films.
Referring to FIG. 2, a second embodiment of the invention is illustrated. A pattern of Litz wire, with wires 24 running perpendicular to wires 22, is laminated between two plastic films 26 and 28, which may be Mylar. The wires 24 and 22 may be woven as if the Litz wires were conventional textile yarns, or may simply be laid together in a rectangular pattern without weaving. Dimensional stability is high since the wire carries most of the load imposed on the laminate, and the laminate is not adversely effected by folding since the fine strands which comprise each individual Litz wire bend easily without kinking.
FIG. 3 illustrates a front view of a parabolic reflector 30, while FIG. 4 illustrates a side view of the same reflector 30. The reflector is composed of I2 gores of laminated material joined at seams 32. One important construction feature to be noted is that one set of the Litz wires, either 22 or 24, must run in the direction of polarization of the radar beam being tracked.
A lightweight R.F. reflective material has been disclosed which folds easily without weakening, has good dimensional stability, has excellent reflectivity, even after severe handling, and is resistant to tearing. Obviously, many modifications and variations are possible in the light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically disclosed.
Iclaim:
ll. A lightweight radio frequency reflective laminate for use in a collapsible antenna comprising:
a first polyester film as a protective outer layer on one side of said laminate;
a second polyester film as a protective outer layer on the other side of said laminate;
said first and second polyester films providing the laminate with good dimensional stability and a high strength to weight ratio;
an open weave of Dacron Yarn material sandwiched between said first and second polyester film said Dacron material providing good dimensional stability, a high strength to weight ratio, and also resistance to tear propagation;
at least one layer of radio frequency reflective aluminum material adjacent said Dacron material and also sandwiched between said first and second polyester films;
said first and second polyester films, said Dacron material and said aluminum reflective material all being joined together to form a unitary laminate.
2. A lightweight radio frequency reflective laminate as set forth in claim 1 wherein:
said open weave material has a leno weave.
3. A lightweight radio frequency reflective laminate as set forth in claim 2 wherein:
said at least one layer ofradio frequency material comprises a thin layer of aluminum foil. 4. A lightweight radio frequency reflective laminate as set forth in claim 3 wherein:
each of said first and second polyester films is comprised of Mylar. 5. A lightweight radio frequency reflective laminate as set forth in claim 4 wherein:
said at least one layer of radio frequency reflective aluminum foil comprises two layers, each of which is sandwiched between said Dacron leno weave material and one of said layers of Mylar. 6. A lightweight radio frequency reflective laminate as set forth in claim 5 wherein:
each of said layers of aluminum foil is 18 mils thick; each of said layers of Mylar is 35 mils thick; and
said Dacron leno weave material is 0.6 ounces per square yard and is l2 4 count. 7. A lightweight radio frequency reflective laminate as set forth in claim 6 wherein:
said laminate composes the reflector ofa collapsible antenna. 8. A lightweight radio frequency reflective laminate as set forth in claim 1 wherein:
said at least one layer of radio frequency reflective material comprises two layers of material, each of which sandwiched between said open weave material and one of said layers of polyester film. 9. A lightweight radio frequency reflective laminate as set forth in claim 8 wherein:
said laminate composes the reflector ofa collapsible anten-

Claims (9)

1. A lightweight radio frequency reflective laminate for use in a collapsible antenna comprising: a first polyester film as a protective outer layer on one side of said laminate; a second polyester film as a protective outer layer on the other side of said laminate; said first and second polyester films providing the laminate with good dimensional stability and a high strength to weight ratio; an open weave of Dacron Yarn material sandwiched between said first and second polyester film said Dacron material providing good dimensional stability, a high strength to weight ratio, and also resistance to tear propagation; at least one layer of radio frequency reflective aluminum material adjacent said Dacron material and also sandwiched between said first and second polyester films; said first and second polyester films, said Dacron material and said aluminum reflective material all being joined together to form a unitary laminate.
2. A lightweight radio frequency reflective laminate as set forth in claim 1 wherein: said open weave material has a leno weave.
3. A lightweight radio frequency reflective laminate as set forth in claim 2 wherein: said at least one layer of radio frequency material comprises a thin layer of aluminum foil.
4. A lightweight radio frequency reflective laminate as set forth in claim 3 wherein: each of said first and second polyester films is comprised of Mylar.
5. A lightweight radio frequency reflective laminate as set forth in claim 4 wherein: said at least one layer of radio frequency reflective aluminum foil comprises two layers, each of which is sandwiched between said Dacron leno weave material and one of said layers of Mylar.
6. A lightweight radio frequency reflective laminate as set forth in claim 5 wherein: each of said layers of aluminum foil is 18 mils thick; each of said layers of Mylar is 35 mils thick; and said Dacron leno weave material is 0.6 ounces per square yard and is 12 X 4 count.
7. A lightweight radio frequency reflective laminate as set forth in claim 6 wherein: said laminate composes the reflector of a collapsible antenna.
8. A lightweight radio frequency reflective laminate as set forth in claim 1 wherein: said at least one layer of radio frequency reflective material comprises two layers of material, each of which sandwiched between said open weave material and one of said layers of polyester film.
9. A lightweight radio frequency reflective laminate as set forth in claim 8 wherein: said laminate composes the reflector of a collapsible antenna.
US766888A 1968-10-11 1968-10-11 Lightweight reflecting material for radar antennas Expired - Lifetime US3587098A (en)

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0010711A1 (en) * 1978-11-02 1980-05-14 Bayer Ag Use of a metallised fabric as a microwave reflector
US4733246A (en) * 1985-09-20 1988-03-22 Eastman Kodak Company Plastic antenna structure having a laminated reflector
EP0298060A3 (en) * 1987-06-30 1989-11-29 Sparbanken Syd A reflector for parabolic antennae
US4987848A (en) * 1987-06-18 1991-01-29 Todd David P Radar reflecting safety flag
US5959595A (en) * 1997-12-04 1999-09-28 Marconi Aerospace Systems, Inc. Antenna metalized fiber mat reflective applique
FR2787244A1 (en) * 1998-12-14 2000-06-16 Cit Alcatel ELECTROMAGNETIC WAVE REFLECTOR FOR TELECOMMUNICATION ANTENNA
US6344835B1 (en) * 2000-04-14 2002-02-05 Harris Corporation Compactly stowable thin continuous surface-based antenna having radial and perimeter stiffeners that deploy and maintain antenna surface in prescribed surface geometry
US6501350B2 (en) 2001-03-27 2002-12-31 Electrolock, Inc. Flat radiating cable
US20040051666A1 (en) * 2001-02-16 2004-03-18 Integral Technologies, Inc. Low cost antennas using conductive plastics or conductive composites
US20040222938A1 (en) * 2003-05-05 2004-11-11 Paul Gierow Inflatable antenna
US6873516B1 (en) * 2001-05-14 2005-03-29 Barry M. Epstein System for protecting a person from the effects of ESD
US20130141307A1 (en) * 2010-05-06 2013-06-06 Michael W. Nurnberger Deployable Satellite Reflector with a Low Passive Intermodulation Design
WO2018094415A1 (en) * 2016-11-21 2018-05-24 eXClaim IP, LLC Environmental sleeve for portable electronic devices

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0010711A1 (en) * 1978-11-02 1980-05-14 Bayer Ag Use of a metallised fabric as a microwave reflector
US4733246A (en) * 1985-09-20 1988-03-22 Eastman Kodak Company Plastic antenna structure having a laminated reflector
US4987848A (en) * 1987-06-18 1991-01-29 Todd David P Radar reflecting safety flag
EP0298060A3 (en) * 1987-06-30 1989-11-29 Sparbanken Syd A reflector for parabolic antennae
AU600147B2 (en) * 1987-06-30 1990-08-02 Sparbanken Syd A reflector for parabolic antennae
US5959595A (en) * 1997-12-04 1999-09-28 Marconi Aerospace Systems, Inc. Antenna metalized fiber mat reflective applique
FR2787244A1 (en) * 1998-12-14 2000-06-16 Cit Alcatel ELECTROMAGNETIC WAVE REFLECTOR FOR TELECOMMUNICATION ANTENNA
EP1014490A1 (en) * 1998-12-14 2000-06-28 Alcatel Electromagnetic wave reflector for telecommunication antenna
US6344835B1 (en) * 2000-04-14 2002-02-05 Harris Corporation Compactly stowable thin continuous surface-based antenna having radial and perimeter stiffeners that deploy and maintain antenna surface in prescribed surface geometry
US20040051666A1 (en) * 2001-02-16 2004-03-18 Integral Technologies, Inc. Low cost antennas using conductive plastics or conductive composites
US6870516B2 (en) * 2001-02-16 2005-03-22 Integral Technologies, Inc. Low cost antennas using conductive plastics or conductive composites
US6501350B2 (en) 2001-03-27 2002-12-31 Electrolock, Inc. Flat radiating cable
US6873516B1 (en) * 2001-05-14 2005-03-29 Barry M. Epstein System for protecting a person from the effects of ESD
US20040222938A1 (en) * 2003-05-05 2004-11-11 Paul Gierow Inflatable antenna
US6963315B2 (en) 2003-05-05 2005-11-08 Srs Technologies, Inc. Inflatable antenna
US20130141307A1 (en) * 2010-05-06 2013-06-06 Michael W. Nurnberger Deployable Satellite Reflector with a Low Passive Intermodulation Design
US9112282B2 (en) * 2010-05-06 2015-08-18 The United States Of America, As Represented By The Secretary Of The Navy Deployable satellite reflector with a low passive intermodulation design
WO2018094415A1 (en) * 2016-11-21 2018-05-24 eXClaim IP, LLC Environmental sleeve for portable electronic devices

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