The traveling-wave linear antenna with nondissipative loading

An approximate theory for a doubly impedance loaded, traveling-wave linear antenna is presented. The distribution of current on the thin, cylindrical antenna is determined approximately in terms of its dimensions and the impedance and position of the lumped impedance loading. From this result, the optimum loading required to excite an outward traveling current wave along most of the cylinder is determined. Significantly, it is indicated that a purely reactive loading may be utilized if its location is properly chosen. Expressions for the input impedance and radiation fields of the traveling-wave antenna are presented. An experimental study is made of a traveling-wave cylindrical antenna utilizing a purely nondissipative loading. Numerical results from the theory are compared with experimental data, and an excellent agreement is noted. The technique described may be utilized to realize a high-efficiency traveling-wave antenna.