Electronically steerable plasma mirror for surveillance radar applications

An alternative to using a phased array to steer a radar beam is to electronically control the orientation of an inertialess broadband microwave reflector. Recent experiments have demonstrated that a planar plasma mirror immersed in a magnetic field, can be formed with electron densities high enough to reflect X-band microwaves. The plasma sheet can be steered in elevation using the magnetic field, and steering in azimuth may be accomplished by designating cathode initiation sites. Retargeting could be achieved in 20 /spl mu/s or less, and a plasma mirror based radar system could be quite affordable. The measured radiation pattern for a 90/spl deg/ reflection from a 50 cm/spl times/60 cm plasma mirror is very similar to that obtained from a metal mirror of comparable dimensions. As a reflector, the plasma mirror exhibits extremely low loss, the reflectivity is very nearly 100%, and the sidelobes are down by >20 dB. A conceptual design for a plasma mirror based radar configuration shows that a -5/spl deg/ to +60/spl deg/ elevation coverage and a 180/spl deg/ azimuthal coverage is obtainable without blockage using a single 1.5 m diameter X-band illuminating dish. Coverage may be extended to +90/spl deg/ elevation angles with minimal blockage, and 360/spl deg/ azimuthal coverage may be obtained with two dishes.