Metamaterial for Low Cost Electronic Scanning, Wideband Conformal Antennas, Cloaking (The Invisible Man), Stealth and Waim

Metamaterials have gained much interest in recent years because they offer the potential to provide low cost electronic scanning antennas and to provide target stealth. Metamaterials are man-made materials in which an array of structures having a size less than a wavelength are embedded. These materials have properties not found in nature, like a negative index of refraction. Much progress has been made using metamaterials.

For Cloaking and Stealthing of Targets: Target cloaking (making them invisible) has been demonstrated at microwaves over a narrow bandwidth using metamaterials. Cloaking has been demonstrated over a 50% bandwidth at L-band using fractal metamaterials. Work on cloaking at optical frequencies will be summarized.Stealthing by absorption using a thin flexible and stretchable metamaterial sheet has been shown to provide 6 dB absorption over an 8 to 10 GHz band, with greater absorption over a narrower band. Using fractals sheets < 1 mm thick simulation has shown a 20dB absorption over a band from 10-15 GHz and 10 dB from 2-20 GHz. Good absorption was achieved for all incident angles and polarizations. It looks very promising for stealthing aircraft and other military targets over a wide band for all aspect angles and polarizations.

For Communication Antennas: Kymeta demonstrated transmission to satellites and back using Ku band antennas which use metamaterial resonators in a very novel way to realize electronic steering potentially at low cost. Echodyne and Metawave (formerly Xerox’s PARC) have developed metamaterial arrays for radar. How Kymeta and Echodyne antennas work is given. The Army Research Laboratory funded the development of a metamaterial 250 to 505 MHz low profile antenna with a lambda/20 thickness for replacement of the very visible tall whip antennas on HMMWVs thus providing greater survivability. Complementing this, a conventional tightly coupled dipole antenna (TCDA) has been developed which provides a 20:1 bandwidth with a lambda/40 thickness. The two together could be employed in escort jammer aircraft like the USA Next Generation Jammer on the Ea-1G Growler covering the band from VHF to Ku band. They could serve as conformal or low profile antennas on the aircraft.

Other Applications: Metamaterial has been used in cell phones to provide antennas that are 5X smaller (1/10th lambda) having 700 MHz to 2.7 GHz bandwidth. Under Army funding isolation equivalent to 1 m separation has been achieved for transmit and receive antennas with 2.5 cm separation allowing simultaneous transmission and reception on a small relay platform. Metamaterial has the potential for use in phased array for wide angle impedance matching (WAIM) by placing metamaterial between the radiating elements to reduce mutual coupling. Using metamaterial one can focus 6X beyond diffraction limit at 0.38 μm (Moore’s Law marches on); 40X diffraction limit, lambda/80, at 375 MHz demonstrated.