Frequency selective surface (FSS) filter for an antenna

• US 5,949,387 A
• Filed: 04/29/1997
• Issued: 09/07/1999
• Est. Priority Date: 04/29/1997
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Bever, Mark E., Macek, John J., Wu, Te-Kao
• Primary Examiner(s): Kim, Robert H.
• Assistant Examiner(s): Lauchman, Layla G.
• Application Number:
  US08/841,185
• Time in Patent Office: 861 Days
• Field of Search: 343/909, 343/754, 343/753, 343/781, 343/893, 343/912, 343/841, 343/725, 343/705, 343/708, 343/910, 333/134, 333/202
• US Class Current: 343/909
• CPC Class Codes: H01Q 15/0026 said selective devices having a stacked geometry or having multiple layers
• CPC Class Codes: H01Q 19/08 for modifying the radiation pattern of a radiating horn in which it is located corrugated horns H01Q13/0208; producing a circular polarisation H01Q13/0241

Abstract

A frequency selective surface filter (20 or 50) particularly useful in connection with a transmit antenna (10) for passing and rejecting signals in multiple frequency bands. According to one embodiment, the frequency selective surface filter (20) has a single conductive screen (24) disposed on a dielectric medium (22). The single-conductive screen (24) includes an array of parallel intersecting lines (26) and (28) providing low frequency filtering. The single-conductive screen (24) also includes an array of double-loop conductive elements each made up of an inner conductive loop (32) and an outer conductive loop (30). According to a second embodiment, the frequency selective surface filter (50) contains two dielectrically separated conductive layers including a first conductive layer (52) having an array of double-slots made up of an inner slot (64) and an outer slot (66). The double-slot configuration further includes a second conductive layer (60) made up of an array of single conductive loops (62).

Claims

1. A frequency selective surface filter for providing multiple frequency rejection bands, said frequency selective surface filter comprising:

a dielectric substrate that is substantially transparent to electromagnetic signal transmission;

a square grid disposed on said dielectric substrate including a first plurality of conductors extending in a first direction and intersecting a second plurality of conductors extending in a second direction which is substantially perpendicular to the first direction, said square grid providing a first frequency rejection band; and

a plurality of double-loop conductive elements, each of said double-loop conductive elements including an inner loop and an outer loop located in each region of the square grid, said outer loop encircling the inner loop, and said first loop providing a second frequency rejection band and said second loop providing a third frequency rejection band.

2. The frequency selective surface filter as defined in claim 1 wherein said dielectric substrate is provided as a thin substantially planar medium.

3. The frequency selective surface filter as defined in claim 1 wherein said inner and outer loops are each configured as square loops.

4. The frequency selective surface filter as defined in claim 1 wherein said frequency selective surface filter is disposed in communication with a multibeam phased array antenna.

5. The frequency selective surface filter as defined in claim 1 wherein said frequency selective surface filter is disposed in communication with a transmit antenna, said frequency selective surface filter filtering out higher frequency harmonics produced by non-linear characteristics of circuitry components in the transmit antenna.

6. A frequency selective surface filter comprising:

a dielectric medium that is substantially transparent to electromagnetic signal transmission and having a top surface and a bottom surface;

an array of double-loop slots provided in a first conductor material on one of the top and bottom surfaces of said dielectric medium, each of said double loop slots including an inner radiating slot encircled by an outer radiating slot for passing signals in a first frequency band and a second frequency band while rejecting signals in a first rejection band; and

an array of conductive loop elements disposed on the other of said top and bottom surfaces of the dielectric layer, for rejecting signals in a second rejection band.

7. The frequency selective surface filter as defined in claim 6 wherein said frequency selective surface filter is disposed in communication with a multibeam phased array antenna.

8. The frequency selective surface filter as defined in claim 6 wherein said frequency selective surface filter is disposed in communication with a transmit antenna, said frequency selective surface filter filtering out higher frequency harmonics produced by non-linear characteristics of circuitry components in the transmit antenna.

9. The frequency selective surface filter as defined in claim 6 wherein said dielectric medium has substantially planar top and bottom surfaces.

10. The frequency selective surface as defined in claim 6 wherein each of said conductive loop elements comprises a single conductive loop.

11. The frequency selective surface as defined in claim 6 wherein said conductive loop elements are configured as square loops.

12. The frequency selective surface as defined in claim 6 wherein said slots each are configured as square loop slots.

13. The frequency selective surface as defined in claim 6 wherein said dielectric medium comprises:

a first thin dielectric substrate providing the top surface; and

a second thin dielectric substrate providing the bottom surface.

14. The frequency selective surface as defined in claim 13 wherein said dielectric medium further comprises a dielectric isolation layer disposed between the first and second thin dielectric substrates.

15. An antenna comprising:

one or more radiating elements for radiating electromagnetic radiation;

transmit circuitry for generating signals for transmission from said one or more radiating elements; and

a frequency selective surface disposed in communication with the one or more radiating elements so as to provide selective frequency filtering, said frequency selective surface filter including a thin dielectric medium that is transparent to electromagnetic signal transmission said frequency surface further including frequency dependent elements for providing multiple frequency rejection bands to reject unwanted signals within the multiple frequency bands.

16. The antenna as defined in claim 15 wherein said frequency selective surface further comprises:

a square grid including a first plurality of conductors extending in a first direction and intersecting a second plurality of conductors extending in a second direction which is substantially perpendicular to the first direction, said square grid providing a first frequency rejection band; and

a plurality of double-loop conductive elements, each of said double-loop conductive elements including an inner loop and an outer loop located in each region of the square grid, said outer loop encircling the inner loop, and said first loop providing a second frequency rejection band and said second loop providing a third frequency rejection band.

17. The antenna as defined in claim 15 wherein said frequency selective surface further comprises:

an array of double-loop slots provided in a first conductor material on one of the top and bottom surfaces of said dielectric medium, each of said double loop slots including an inner radiating slot encircled by an outer radiating slot for passing signals in a first frequency band and a second frequency band while rejecting signals in a first rejection band; and

an array of conductive loop elements disposed on the other of said top and bottom surfaces of the dielectric layer, for rejecting signals in a second rejection band.

18. The antenna as defined in claim 15 wherein said one or more radiating elements comprises a multibeam phased array.