Antenna having electrically controllable radar cross-section

• US 6,300,894 B1
• Filed: 07/09/1999
• Issued: 10/09/2001
• Est. Priority Date: 07/09/1999
• Status: Expired due to Term

• Current Assignee: North South Holdings Incorporated (Spherix Incorporated)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Walley, George M., Lynch, Michael J., Newton, Charles M.
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US09/350,482
• Time in Patent Office: 823 Days
• Field of Search: 342/1, 342/2, 342/3, 342/4, 342/5, 342/6, 342/7, 342/11, 342/13
• US Class Current: 342/13
• CPC Class Codes: G01S 7/38 Jamming means, e.g. producing false echoes
• CPC Class Codes: H01Q 15/148 with means for varying the reflecting properties H01Q15/147 takes precedence

Abstract

An RF interface is configured as a laminate structure having a core layer of a ferromagnetic ceramic material, such as barium strontium titanate, whose permitivity is electrically controllable to modify the behavior of impinging electromagnetic energy, as one of minimally attenuated transmission, maximally attenuated absorption, and highly unattenuated reflection. Opposite surfaces of the ceramic core are coated with an electrically lossy material, such as indium tin oxide, to which a differential DC voltage is applied, and thereby imparting a DC electric field to the core layer. For an antenna application, during transmit/receive mode, the differential voltage has a magnitude that renders the laminate'"'"'s core highly conductive, and thereby reflective to the RF wavelength being sourced from or received by an associated feed horn. During other times, the differential voltage renders the laminate effectively transparent to RF wavelengths in a prescribed band of interest (e.g., a search radar emanating from a threat platform, such as an aircraft).

Claims

1. An RF energy interface comprising a laminate structure of a core layer of ferromagnetic ceramic material, having a permitivity that is electrically controllable to modify the behavior of impinging electromagnetic energy, opposite surfaces of said ceramic core having an electrically conductive material thereon, and a differential DC voltage applicator coupled thereto so as to impart a differential voltage to said core layer, said applicator being operative, during transmit/receive mode of an antenna application to set said differential voltage at a first value that renders said laminate structure reflective to RF energy, and during other times, to set said differential voltage at a second value that renders said laminate structure effectively transparent to said RF energy, and during transmit/receive mode of a radome application, being operative to set said differential voltage at a third value that renders said laminate effectively transparent to RF energy, and during other times, to set said differential voltage at a fourth value that is effective to render said laminate effectively absorbent of said RF energy.

2. An RF energy interface according to claim 1, wherein said core layer comprises barium strontium titanate.

3. A radome for an antenna housed therein comprising a multi-laminate structure of plural layers of ferromagnetic ceramic material, each having a permitivity that is electrically controllable to modify the behavior of impinging electromagnetic energy, opposite surfaces of said layers of ceramic material having electrically conductive material thereon, and a differential DC voltage applicator coupled thereto so as to impart differential DC voltages across said layers, said applicator being operative, during transmit/receive mode of said antenna to set said differential voltages at a first value that renders said multi-laminate structure reflective to RF energy, and during other times, to set said differential voltages at a second value that renders said multi-laminate structure effectively transparent to said RF energy.

4. An apparatus for controllably interfacing radio waves incident upon a prescribed spatial region comprising:

an electrically controlled structure having a first and second opposite surfaces, and containing one or more layers of material therebetween whose transmissivity for said radio waves is electrically alterable by a DC electrical field applied thereacross;

a first electrode that is effectively transparent to said radio waves and having a first side thereof disposed on a layer of said material at said first surface of said structure, and wherein no layer of said material is disposed on a second side of said first electrode opposite to said first side thereof;

a second electrode that is effectively transparent to said radio waves having a first side thereof disposed on a layer of said material at said second surface of said structure, and wherein no layer of said material is disposed on a second side of said second electrode opposite to said first side thereof;

a radio wave transmissivity controller being operative to couple to said first and second electrodes a DC voltage that makes said structure selectively one of transparent, absorptive and reflective to said radio waves incident thereon.

5. An apparatus according to claim 4, wherein said radio wave transmissivity controller is operative to couple to said first and second electrodes a DC voltage that makes said structure transparent to said radio waves incident thereon.

6. An apparatus according to claim 4, wherein said radio wave transmissivity controller is operative to couple to said first and second electrodes a DC voltage that makes said structure absorptive to said radio waves incident thereon.

7. An apparatus according to claim 4, wherein said radio wave transmissivity controller is operative to couple to said first and second electrodes a DC voltage that makes said structure reflective to said radio waves incident thereon.

8. An apparatus according to claim 4, wherein said material comprises barium strontium titanate.

9. A method for controllably interfacing radio waves incident upon a prescribed spatial region comprising the steps of:

(a) providing an electrically controlled structure having

a first and second opposite surfaces, and containing one or more layers of material therebetween whose transmissivity for said radio waves is electrically alterable by a DC electrical field applied thereacross;

a first electrode that is effectively transparent to said radio waves and having a first side thereof disposed on a layer of said material at said first surface of said structure, and wherein no layer of said material is disposed on a second side of said first electrode opposite to said first side thereof;

a second electrode that is effectively transparent to said radio waves having a first side thereof disposed on a layer of said material at said second surface of said structure, and wherein no layer of said material is disposed on a second side of said second electrode opposite to said first side thereof; and

(b) applying a selected DC voltage to said first and second electrodes, by coupling thereto,

(b1) for a first mode of operation, a first prescribed DC voltage that makes said structure effectively transparent to said radio waves;

(b2) for a second mode of operation, a second prescribed DC voltage that makes said structure effectively reflective to said radio waves; and

(b3) for a third mode of operation, a third prescribed DC voltage that makes said structure effectively absoprtive of said radio waves.

10. A method according to claim 9, wherein said material comprises barium strontium titanate.