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United States Patent   Patent Number: 5,313,221
Denton, Jr.  Date of Patent: May 17,1994
 SELF-DEPLOYABLE PHASED ARRAY RADAR ANTENNA
 Inventor: Robert J. Denton, Jr., Rome, N.Y.
 Assignee: The United States of America as represented by the Secretary of the Air Force, Washington, D.C.
 Appl. No.: 902,107
 Filed: Jun. 22,1992
 Int. CI.* H01Q 1/48
 U.S. CI 343/846; 343/881;
 Field of Search 343/846, 877, 825, 826,
343/827, 829, 848, 880, 881, 900, 888; H01Q
 References Cited
U.S. PATENT DOCUMENTS
1,689,400 3/1922 Manley 343/866
1,696,402 8/1924 Horton 343/866
3,509,570 4/1970 Lindsey et al 343/888
3,978,410 8/1976 Fletcher et al 343/705
4,220,956 9/1980 Sanford 343/806
4,412,221 10/1983 Stapleton 343/708
Primary Examiner—Donald Hajec
Assistant Examiner—Hoanganh Le
Attorney, Agent, or Firm—Stanton E. Collier; Donald J.
A phased array monopole antenna has a single layer membrane upon which a plurality of antenna units are attached. Each antenna unit has a flexible curved antenna blade which bends over or springs up when the membrane is rolled or unrolled on a drum.
2 Claims, 2 Drawing Sheets
U.S. Patent May 17, 1994 Sheet 2 of 2 5,313,221
SELF-DEPLOYABLE PHASED ARRAY RADAR
STATEMENT OF GOVERNMENT INTEREST 5
The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment of any royalty thereon.
BACKGROUND OF THE INVENTION 10
The present invention relates to phased array radar technology, and, more particularly, relates to a spacefed phased array radar antenna employing the window shade deployment technique for use in a space-based 15 radar.
The current state-of-the-art technology includes a window shade deployed space-fed phased array radar antenna which is particularly suited for use in space. The rolled antenna is advantageous because it mini- 20 mizes storage space aboard a spacecraft, such as a satellite, where available space is at a minimum. This is because, when in a stowed position, it minimizes the amount of space required in a launch vehicle. When the spacecraft achieves a selected orbit, the antenna is de- 25 ployed and the window shade structure is unrolled to a fully expanded operative condition. Such an antenna may consist of a low to medium power RF feed which illuminates a lens aperture membrane. Active transmit/receive (T/R) modules in the aperture membrane re- 30 ceive radar pulses from the feed, perform beam-steering phase shifts, amplify them and re-transmit the signal towards a target of interest on the ground or in the air.
The reflected energy is received in reverse order, being amplified by the T/R modules and then focused ^ back into the space feed. Radar processors and the supporting subsystems are part of the satellite bus and may be located in the feed or at the base of a feed mast. In line with current technology, the aperture consists of a tensioned membrane consisting of three separate equally spaced layers, which provides for a very lightweight, yet sufficiently flat, aperture plane. Array flatness requirements for the space-fed approach are less severe than for corporate-fed approaches by an order of 4J magnitude. The membrane aperture can be rolled up onto a drum, resulting in a simple, compact, and repeatable method for deployment and retraction of the antenna.
Although this technique may seem appropriate, there J0 are several potential problems with the technology. First of all, although the three-layer membrane conforms to the weight and flatness requirements necessary for a space-fed lens space-based radar, it is extremely complex to manufacture. This is due primarily to the 55 three separate layers inherent in the design, as well as the many different parts and connections necessary between these parts. The layers are equally spaced on depoloyment (separated by J wavelength) and come together when stowed. Electronics embedded in the 60 middle layer must be connected to the antenna elements on the outside layers. This also adversely affects the performance reliability of the radar. Another area of concern is the type of antenna radiating element used—a dipole. The antenna pattern of a monopole is much 65 more applicable for a space-based radar mission. Thus, there is a need to develop a monopole antenna structure for use in space-based radars.
SUMMARY OF THE INVENTION
The present invention provides a phased array monopole antenna for use in a space-based radar design, incorporating a space-fed aperture membrane.
The invention comprises a flexible single-layer membrane, (This single layer may and generally will be a composite of several layers of material) upon which are mounted a plurality of monopole antenna units. Each of these antenna units has a ground plane, an antenna mounting base mounted thereon, and a flexible monopole antenna blade mounted in the base. In actuality, the ground planes of each of the antenna units would form one large, common ground plane. The antenna may be connected to a RF connector or directly into a T/R module, as in the space-fed arrangement previously discussed. The membrane with these monopole antenna units thereon may be rolled up or rolled out using a window shade-like apparatus. The antenna blades, which are perpendicular to the membrane, bend over upon retraction of the membrane and spring up upon deployment of such.
Therefore, one objective of the present invention is to provide an improved space-based radar antenna using monopole antennae.
Another objective of the present invention is to provide a phased array antenna structure using monopole antennae.
Another objective of the present invention is to provide an improved antenna structure having monopole antennae and a single-layer membrane for support thereof.
Another objective of the present invention is to provide an improved antenna structure wherein the antenna blade self-deploys and/or retracts with the deployment/retraction movement of the membrane.
Another objective of the present invention is to provide an improved antenna structure having fewer electrical connections and simpler construction considerations.
These and many other objectives and advantages of the present invention will be readily apparent to on skilled in the pertinent art from the following detailed description of a preferred embodiment of the invention and the related drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates, by perspective view, the present invention.
FIG. 2 is a side view of the present invention. FIG. 3A is a top view of the antenna blade showing its curvature.
FIG. 3B is cross section through the antenna mounting base with the antenna blade mounted thereon of the present invention.
FIG. 3C illustrates the antenna blade counter-sunk in the antenna mounting base with a bending surface therein.
FIG. 4 illustrates the deployment of the present invention by the window shade technique.
DESCRIPTION OF THE PREFERRED
Referring to FIG. 4, a flexible single layer membrane 10 is shown partially deployed. The membrane 10 is stored on a drum 12 that operates like a window shade. Electromechanically operated telescoping towers 14 have a cross beam 16, attached thereon which is at