Research may yield more compact antennas for military use

While tall, bulky antennas seem like relics in an era of sleek, modern smartphones, they're still an unfortunate necessity for American soldiers. "One of the problems that many military systems have is that they use low frequencies — anywhere from 2 MHz to below 1 GHz," says Nader Behdad , an assistant professor of electrical and computer engineering at the University of Wisconsin-Madison. "As a result, very often you see huge antennas sticking off of their vehicles." Behdad thinks that those enormous antennas could be scrapped for low-profile, broadband antennas — thanks to a different approach to antenna design that replaces large dipole antennas with a more compact and conformal multi-mode radiator. The Office of Naval Research agreed, giving Behdad a three-year, $510,000 research award through its young-investigator program, allowing his to develop the next generation of antennas for its vehicles. With traditional dipole antennas, the lower the operating frequency of an antenna, the larger it needs to be. Rather than fighting the laws of physics and trying to lower the operating frequency of a single antenna, Behdad's concept involves tuning multiple parts of the same antenna structure to radiate at different frequencies, using synthetic "metamaterials" to shape their radiation patterns so that they won't interfere with one another. Composed of metals, dielectrics and other materials, metamaterials react to electromagnetic waves differently, based on their index of refraction, making it possible to manipulate two competing radiation patterns and make them work in tandem within one antenna.