Frequency selective surface (FSS)

• US 5,208,603 A
• Filed: 06/15/1990
• Issued: 05/04/1993
• Est. Priority Date: 06/15/1990
• Status: Expired due to Term

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Yee, James S.
• Primary Examiner(s): Hille, Rolf
• Assistant Examiner(s): BROWN, PETER T
• Application Number:
  US07/539,018
• Time in Patent Office: 1,054 Days
• Field of Search: 343/700, 343/909, 343/872, 343/753, 343/754, 343/755, 343/767, 343/770, 343/771, 343/778
• US Class Current: 343/909
• CPC Class Codes: H01Q 1/286 substantially flush mounted with the skin of the craft
• CPC Class Codes: H01Q 15/0026 said selective devices having a stacked geometry or having multiple layers

Abstract

A frequency selective surface (FSS) for incorporation into the outer skin of an aircraft, for transmitting electromagnetic energy in a predetermined frequency band. The FSS includes three layers sandwiched together with a dielectric material. Arrays of apertures are formed in the two outer layers, which are conductive. The inner layer consists of patches of conductive material. The apertures and patches are in substantial alignment with one another. The apertures and patches can have the shapes of crossed-dipoles, circles, squares, tripoles and Jerusalem crosses. In a preferred embodiment, the shapes of the apertures and patches are geometrically congruent. A dual-band FSS, having apertures and corresponding patches in two different sizes and spacings, can transmit two separate frequency bands.

Claims

1. A frequency selective surface for transmitting a discrete frequency of incident electromagnetic energy, comprising:

slots in spaced conductive sheets aligned with one another and separated by a solid dielectric material, the slots being tuned at a discrete frequency to function as a high pass filter; and

a patch element within the dielectric material tuned to the discrete frequency and functioning as a low pass filter for passing energy received by one slot to the other slot through the dielectric material.

2. A frequency selective surface element for transmitting a discrete frequency of incident electromagnetic energy, comprising:

(a) a first conductive ground plane including a first aperture of a predetermined size and shape tuned to receive energy at the discrete frequency and functioning as a high pass filter;

(b) a layer of solid dielectric material attached to the ground plane;

(c) a patch shaped and sized to substantially match the first aperture for coupling with the discrete frequency and functioning as a low pass filter, the patch being positioned on the dielectric layer aligned with and remote from the first aperture;

(d) a second layer of dielectric material overlying the patch; and

(e) a second conductive ground plane having a second aperture of a predetermined size and shape tuned to the discrete frequency, the second aperture being aligned with and remote from the patch and first aperture on the second dielectric layer so that incident electromagnetic energy at the discrete frequency is transmitted through the surface from the first aperture to the patch to the second aperture.

3. A frequency selective surface comprising a plurality of the elements of claim 2 arranged in a predetermined geometric pattern.

4. A frequency selective surface element for transmitting two discrete frequencies of incident electromagnetic energy comprising a sandwich structure having outer ground planes of conductive material around a central patch plane, the ground planes being isolated from the patch plane and from each other by a solid dielectric material and having analogous, high pass apertures aligned with one another, each ground plane including a first aperture of predetermined size and shape tuned to a first frequency and a second aperture of different size and shape tuned to a second frequency, the patch plane functioning as a low pass filter and including a first patch element being the inverse of the first aperture and a second patch element being the inverse of the second aperture, the patch elements being aligned with the respective apertures of the ground planes and being electrically isolated from one another.

5. A frequency selective surface tuned to pass either or both of two predetermined frequencies comprising a plurality of elements of claim 4 arranged in a predetermined geometric pattern.