Theoretical analysis on radiation and reception characteristics of an oblate spheroidal antenna for electron plasma waves

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Abstract
The radiation and reception characteristics of the oblate spheroidal antenna for electron plasma waves are theoretically investigated. The analysis is carried out as a boundary‐value problem. The formulas for the radiation and reception characteristics such as radiation impedance, electron charge distributions, radiated wave potential, directional properties, and receiving voltage of the oblate spheroidal antenna are analytically obtained. As a result, it is concluded that the radiation and reception characteristics of the antennas are not uniquely determined by kpa (kp is the wave number of an electron plasma wave, and a is the radius of the circular‐plate antenna), but are determined by two out of three factors, kpa, ζ (radius divided by Debye length), and ω/ωp (angular signal frequency to angular plasma frequency). This conclusion is in marked contrast to the conventional theory in which the charge distribution on the antenna is assumed a priori as uniform and, thus, the antenna characteristics are uniquely determined by kpa. It is claimed that the experimental results obtained hitherto support the present new theory.