United Staes Patent / US 4999637 A / 1991
A method for forming a cloud of artificial ionization above the earth by initially heating the resident plasma at a desired altitude with electromagnetic radiation having a frequency approximately the same as that of the ambient plasma. As the plasma frequency increases due to heating, the radiation frequency is also increased until the final maintenance frequency is attained.
Self-focusing antenna system
US 3174150 A
SELF-FOCUSING ANTENNA SYSTEM March 16, 1965 Filed June 29, 1962