US3509576A - Collapsible parabolic antenna formed of a series of truncated fabric cones - Google Patents

Description

April 28, 1970 E. M LAIN 3,

CULLAPSIBLE PARABOLIC ANTENNA FORMED OF A SERIES 0F TRUNCATED FABRIC CONES 3 Sheets-Sheet 1 Filed Dec. 4, 1967 :EEEEIE ar f ..6 g J, F T.

FIG 3 INVENTOR. GEORGE E. MCLAIN Agent Apri G; E. MOLAIN 3,509,576

COLLAPSIBLE PARABOLIC ANTENNAFORMED OF A SERIES OF TRUNCATED FABRIC CONES Filed Dec. 4. 1967 3 Sheets-Sheet 2 INVENTORI. GEORGE E. MCLAIN Agent a; E; M LAIN 3 9 576 COLLAPSIBLE PARABOLIC ANTENNA FORMED A SERIES 7 April 28, 1970 OF TRUNCATED FABRIC CONES 3 Sheets-Sheet 5 Filed D80. 4, 1967 INVENTOR. GEORGE E. MCLAIN Agent United States Patent Ofice 3,509,576 Patented Apr. 28, 1970 U.S. Cl. 343840 2 Claims ABSTRACT OF THE DISCLOSURE The approximation of a. parabolic electromagnetic re,

cal arrangements necessary to produce an extenda'bl weight and flexible sheet of material to form a space reflector. Schemes have been developed for deploying objects such as antennas, radar reflectors and other similar devices into the earths upper atmosphere and the regions of outer space. Antennas and the like are highly important in the communications field, since electromagnetic waves of radio, television and radar can be transmitted from one point of the earths surface to the antenna and they reflected or bounced back to another point of the earths surface. By this method of transmission the range of communications can be greatly increased.

It is well known that a paraboloidal reflector for use with electromagnetic energy is highly desirable but as yet a large, collapsible, truly paroboloida-l reflector for space application has not been built. A truly paraboloidal. reflective surface will permit a greater amount. of. fin phase electromagnetic energy to reach the feedcone and:

related electronic systems. Also, to increase the gain of an'antenna, it is desirable to increase. its surface tareazas;

well as. to correctlyvposition the feed cone at the igeoa metric focal point of the parabola.

Typically, to form and support a par-aboloidal reflector,

a large mass of support structure is required which would be unsuitable for space application because of the weight antenna design engineers wonldil then provide a great number of truncatei cones which would more closely ap supported on extendable boo-ms or flex-iblenribs or else are made from flat surface materials fastened between shaped supports in an attempt to approximate a parabolic reflector. As increasingly large antennas are required to fulfill the requirements of space missions, present extendable antennas are not acceptable because as surface areas of the antenna increases, additional support members are needed to hold the antenna shape thereby increasing weight. It is also known that differences in thermal expansion between the support members and the reflective material distorts the reflective surface, and an increase in the number of support members compounds this problem.

It is therefore the object of the present invention to provide a close approximation of an extendable, para boloidal reflector by using a plurality of interconnected.

truncated cones supported by extendable members.

One object of the present invention is to provide an extendable antenna for space application which will have a greater gain to weight ratio than any existing space antenna of comparable size.

Another object of the present invention is to provide an extendable antenna for space application which will have a greater gain to weight ratio than any existing space antenna of comparable :size.

Another object of the present invention is to provide a method of supporting the reflective surface on a plurality of support members without actual physical contact thereby reducing. reflective surface thermal distortion.

show an antenna structure encompassed by the present invention. A radiator 3 is mounted on a center support hub 12 from which electromagnetic energy is fed via radiator support member 4. A foldable reflector 11 is operably connected to and supported by a plurality of ex tendable reflector support members 14. Reflector support members 14 could be of the so called lazy tong type as shown, or other extendable mechanisms which are available.

Reflector 11 is made from a foldable, electromagnetic reflective material capable of being formed into the shape of a truncated cone. A plurality of truncated cones 13a, 13b, 13c 13d, 132 and 13 are fashioned together to produce a large integral reflector 11. The exact number of truncated cones used and their sizewould depend upon the ultimate size. of reflector 111 aswell as the electrical 1 characteristics and. bandwidth of i electromagnetic. signal: to be re e The center portion or baseuls of ee. madelof a so rdireflective material aS lti lS not necessja-yufor base 1 5,;to extend.-1"heuse of a solid base 15 will also provide a firm anchor for. the center of the flexible fabric from which reflector 11 is made. If a very short wave length electromagnetic signal is to be reflectedfromreflector 111 it would be desirable. to have as perfect a paraboloidal reflector as possible. The

proximate a parabcloidal reflector increasing reflectance perfection. On the other hand, if a relatively long wave length signal is to be reflected, the design engineer could select fewer. (and larger) truncated cones since a high degree of reflectance perfection is not necessary.

Reflector 11 is attached to extendable members -14 by carefully manipulated rigging 16 to insure that each truncated cone section 13a, 13b, 13c and so on will remain true. In many instances double rigging for a particular truncated cone will be necessary to insure the needed tautness, as well as the needed alignment to maintain a true truncated cone. Each adjacent truncated cone which together forms an integral reflector 11 is sewn or fastened together. The outer portion or edge of one cone is operably securedor fastened to the inner portion or edge of the next adjacent cone. At the junction 20 between adjacent comes, as .best zseen in FIGURES 4 and 5, a plurality of outwardly extending semicircular support por-w tions 18 made ota cloth or mesh s prov ed. The inner.

area of semicircular portions 18 is secured by sewing or tying semicircular portions 18 to reflector 11 at junctions 20. The outer regions of semicircular portion 18 form a plurality of apex points 19 which are operatively received to respective support members 14. The result of this type of support is that an equal load distribution at the junction 20 of adjacent truncated cones is provided by the outwardly extending semicircular support portions 18. By utilizing this type of support for reflector 11, a close approximation of a paraboloidal reflector can be constructed and maintained with a minimum of support members 14. Also, since the surface of reflector 11 does not directly corne into contact with support members 14, any

thermal, distortion in the support member will be more evenly distributed over the surface pt reflector 11, there by reducing overall distortion. Thermal distortion could be further reduced by the use of springs (not shown) as an interconnect between apex points 19 and supports 14. In addition to the semicircular shaped material supporting each cone, additional rigging lines 16 may be needed, especially on the extreme outer and inner cones to maintain a true shape.

The number of support members 14 and their length would of course be determined by the size of the antenna to be launched into space. In any event, a fewer number of support members 14 is needed to support a large extendable antenna than with other known schemes of extendable antenna by using the rigging system as shown.

FIGURE 3 shows the entire system in its folded configuration, housed in a space vehicle. It may be desirable to secure the entire system with a wire 21 which can be severed on command from a remote location.

It is also envisioned that large extendable antennas of the type herein described could be stowed on the back of small land vehicles for use in emergency when it would be desirable to set up communication links in the event of disasters, for example, floods or hurricanes.

While a particular arrangement of the present invention has been illustrated above by Way of example and the invention could be modifiedby using equivalent st1 uc- .ture from that .described to support a series of truncated cones for a large extendable antenna for use in space application.

What is claimed is: 1. An extendable antenna structure comprising: a foldable reflector having a plurality of truncated cone members of an electromagnetic reflective material; interconnect means for operably interconnecting said plurality of truncated cone members at junctions at opposing edges to form an integral reflective surface which closely approximates a paraboloid;

support means comprising a radial array of extensible links; and, securing means extending between and securing said reflector to said extensible support means for UNITED STATES PATENTS 2,325,765 8/1943 Gartenmeister 343-9l5 3,174,397 3/1965 Sanborn 343-915 3,337,871 8/1967 Greenberg et al. 343-915 3,406,404 10/1968 Maier 343-915 ELI LIEBERMAN, Primary Examiner U.S. Cl. X.R. 3439l5

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