Radio Antenna Made of Plasma

A radio antenna made of electrified gas could lead to stealthy, jamming-resistant transmitters, research now reveals.

Electrified gas, or plasma, makes up stars and lightning and is what sheds light in fluorescent bulbs. Sealed glass, ceramic or even flexible plastic tubes of plasma can behave just like conventional metal antennas.

Scientists are now developing remarkably simple and rugged plasma antenna prototypes that could soon find use in the military or telecommunications.

These antennas only work when energized, effectively vanishing when turned off, with the plasma reverting back to normal gas. This is key for stealth on the battlefield—metal antennas can scatter incoming radar signals, giving away their presence.

In addition, to counteract jamming attempts, plasma antennas can rapidly adjust which frequencies they broadcast and pick up by changing how much energy the plasma is given. This way, they avoid interference from enemy signals. Metal antennas, on the other hand, are each forced to receive and transmit only a given range of frequencies, making them vulnerable to jamming.

The fact that plasma antennas can get reconfigured to broadcast and receive a wide range of frequencies also means "you can create a kind of 'all-in-one' antenna, with one plasma antenna performing the jobs of several metal antennas," researcher Theodore Anderson, CEO of plasma antenna company Haleakala R&D in Brookfield, Mass., told LiveScience. "We're pursuing telecommunications as well as military applications."

These plasma antennas use inert noble gases such as neon, and do not get very hot when turned on. Anderson and his colleagues are currently experimenting with plasma in glass tubes, but to make them more rugged, they plan in the future to use ceramic tubes encased in heat-resistant synthetic foam "almost as hard as steel," he said.

The scientists are currently developing a "smart" plasma antenna that can steer a beam of radio waves 360 degrees to scan a region and then find and lock onto transmitting antennas. A comparable radio array using metal antennas would be much larger and heavier, Anderson said. The scientists plan to complete their commercial prototype by the end of November 2008.

The researchers detailed their findings Nov. 12 at the American Physical Society's plasma physics division meeting in Orlando.

• Quiz: Great Inventions
• The Incredible Shrinking Radio
• Gallery: Micromachines