BACKGROUND

So-called horn antennas—which may be considered as flared waveguides—are commonly used in many RF application, as they afford a number of benefits. These benefits include simple construction, relatively adequate directivity of beam pattern, bandwidth of about 10%, and the potential relatively high gain when used in conjunction with a parabolic reflector.

Horn antennas, however, are subject to a number of significant disadvantages. For example, horn antennas typically radiate energy having a spherical wave front shape. As a result, such horn antenna produces beams (radiation lobe patterns) with limited or poor directivity. Moreover, such horn antennas typically have limited gain—unless used with a large form-factor parabolic reflector. The typical gain limit of a horn antenna is approximately 20 dB due to the fact that in order to increase the gain, the whole size of the horn is increased. Increasing the size of the horn opening produces a commensurate increase in the length of the horn. At some point the length of the horn becomes excessive or impractical.

SUMMARY

The present disclosure is directed to systems and techniques that provide for enhanced gain and radiation characteristics of antennas. The systems and techniques employ layers or cards of fractal plasmonic surfaces (“FPS cards”) to provide gain to the antennas. The fractal plasmonic surfaces each include a close-packed arrangement of resonators having self-similar or fractal shapes, which may be referred to as “fractal cells.” The fractal cells are placed sufficiently close to one another (e.g., less than ⅙ wavelength, ⅛ wavelength, 1/10 wavelength, 1/12 wavelength, 1/15 wavelength, 1/16 wavelength, 1/20 wavelength) so that a surface (plasmonic) wave causes near replication of current present in one fractal cell in an adjacent fractal cell. A fractal of such a fractal cell can be of any suitable fractal shape and may have two or more iterations. The fractal cells may lie on a flat or curved sheet or layer and be composed in layers for wide bandwidth or multi-bandwidth transmission. The area of a surface (e.g., sheet) and its number of fractals determines the gain relative to a single fractal cell. As each cell is fed plasmonically (via plasmonic coupling) rather than directly, “dead” or covered or out of resonance cells do not alter the ability of the other cells to work. The boundary edges or faces of the surface may be terminated resistively so as to not degrade the cell performance at the edges. These surfaces may be referred to as fractal plasmonic surfaces and can provide benefits for gain, field emission, directivity, increased bandwidth, power delivery, and/or heat management. The one or more FPS cards are positioned near or adjacent to one or more antennas so as to provide improved gain and/or directivity for the one or more antennas. A frame can be used to hold the one or more FPS cards. One or more layers or cards of dielectric material may be used with the FPS card(s) in some embodiments. The one or more FPS cards, and the one or more dielectric cards (when present), may be used with the frame as a retrofit apparatus, system, or kit for application to one or more preexisting antennas in exemplary embodiments of the present disclosure.

Exemplary embodiments of the present disclosure can provide techniques, including systems and/or methods, for improving the gain and directivity of preexisting antennas. Representative frequencies of operation can include, but are not limited to, those over a range of 500 MHz to 1.3 GHz, though others may of course be realized: e.g., 5.9 GHz, 600 MHz to 6 GHZ; 3.3 GHz to 4.2 GHz; in millimeter-wave bands, e.g., 24-86 GHz, including 26 GHz, 28 GHz, 38 GHz, and 42 GHz, 27.5-28.35 GHz, 27-40 GHz, 26.5-29.5 GHz, 27.5-28.28 GHz, 24.25-27.f GHz, 37-43.5 GHz, 26.5-27.5 GHz, 24.5-27.5 GHz; as well as bands at (or bracketing) 600 MHz, 700 MHz, 800 MHz, 900 MHz, 1.5 GHz, 2.1 GHz, 2.3 GHz and 2.6 GHz, as just some examples. Operation at other frequencies, including for example those of visible light, infrared, ultraviolet, and as well as microwave EM radiation, e.g., K, Ka, X-bands, etc. may be realized, e.g., by appropriate scaling of dimensions and selection of shape of the resonator elements. In some embodiments, the effects produced by such techniques can include cloaking, obfuscation, obscuration, or invisibility of an object at the noted wavelengths or bands.

It should be understood that other embodiments of FPS systems and methods according to the present disclosure will become readily apparent to those skilled in the art from the following detailed description, wherein exemplary embodiments are shown and described by way of illustration. The systems and methods of the present disclosure are capable of other and different embodiments, and details of such are capable of modification in various other respects. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive.

These, as well as other components, steps, features, objects, benefits, and advantages, will now become clear from a review of the following detailed description of illustrative embodiments, the accompanying drawings, and the claims.

