A plasma stealth antenna for the US Navy

Summary form only given, as follows. We have received a Phase 1 SBIR contract from the US Navy to develop a plasma stealth antenna. The concept is to use plasma discharge tubes as antenna elements. When the tubes are energized, they become conductors and can transmit and receive radio signals. When they are de-energized, they revert to nonconducting elements (in present tests, glass tubes), and do not reflect probing radio signals. The reflection problem is most acute for probing signals near the resonant frequency of the antenna, which produces a large reflection cross section. A second feature of the plasma antenna, is that it can be reconfigured during operation, by selectively energizing only some of the elements. It can therefore be "steered" electronically. This cannot be done with metal conductor antennas. A third feature of the plasma antenna, is that it can be turned off rapidly, reducing ringing on pulse transmission. Preliminary tests before receiving the SBIR successfully demonstrated both the operation of the antenna in transmission and reception, and the stealth features on a Navy test range in San Diego. The tubes used in that demonstration were modified neon sign discharge tubes filled with helium, neon, argon, and a neon-argon mixture. More detailed experiments are under way to explore such topics as optimizing the system with respect to antenna-feeder coupling, radiation-pattern peaking, and signal-to-noise ratio.