On the feasibility of microwave produced Bragg reflector for the OTH radar application

Summary form only, given. A series of chamber experiments was conducted to investigate three major issues concerning the feasibility of using microwave-produced atmospheric plasma layers as a supplemental reflector for the OTH radar. These include (1) the effectiveness of the plasma layers as a Bragg reflector, (2) the propagation of high-power microwave pulse, and (3) the lifetime of the plasma. Experiments were conducted in a large chamber made of a 2-ft cube of Plexiglas and filled with dry air to a pressure comparable to the upper atmosphere. Two microwave beams (3.27 GHz) generated by a single magnetron tube were fed into the cube, with parallel polarization direction, by two S-band microwave horns placed at right angles to the adjacent sides. A set of parallel plasma layers was then generated in the central region of the chamber where the two beams intersect. A Bragg scattering experiment was then performed using the plasma layers as a Bragg reflector. The experiment results were found to agree very well with the theory, which predicts effective Bragg scattering. The results show that after the first 70 μs the attachment rate is balanced by the detachment rate and the loss of free electrons is mainly determined by the acceptable electron ion recombination rate