Advanced Antennas Enabled by Electromagnetic Metamaterials

Much attention has been given to electromagnetic metamaterials over the past decade, as researchers have investigated promises of invisibility cloaks and flat lenses, along with other dramatic claims. More recent work has focused on improving existing devices by employing metamaterials in their design and construction. These recent efforts have begun to show truly practical applications of metamaterials in real-world devices, giving such benefits as increased operating bandwidth and reduced weight. Specifically, metamaterial surfaces, or mctasurfaccs show great promise in improving the performance of radio-frequency RF and microwave antennas. Properly designed mctasurfaces can be included as liners for horn antennas to support hybrid modes, which yield rotationally symmetric radiation patterns with minimal cross-polarization. Such radiation characteristics arc desirable for satellite reflector antennas, where reducing the size and weight of antennas corresponds to a dramatic reduction in costs. These satellite antennas often use separate polarizations as separate communication channels, effectively providing nearly double the communications data bandwidth through a single antenna. Traditionally, corrugated horns provide low cross-polarization, but they arc very expensive to manufacture and arc very heavy. Here we show a conical horn antenna with metamaterial liners operating over an octave bandwidth including the i-band with cross-polarization better than 30 dB. The metamaterials add virtually no loss to the horn, while exceeding the bandwidth of a corrugated horn and requiring a fraction of the weight. To achieve this excellent performance, we developed the metamaterial surface designs, mode analyses for circular mctasurfacc-lined waveguides, as well as an analysis of mctahorns with various methods for tapering the inhomogencous metamaterial properties along the length of the horns.