Circular Loop Antennas Reactively Loaded for a Uniform Traveling-Wave Current Distribution

Abstract

It is demonstrated that a uniform traveling-wave current distribution on a circular loop of one-wavelength circumference can be obtained by loading the loop with a lumped reactance at a position of 45/spl deg/ away from the feed point. To achieve a uniform traveling-wave current distribution, the loading reactance and the input impedances of the loaded and unloaded loop antennas need to satisfy certain relations from which the loading reactance can be predicted theoretically. It is shown that the circular loop antenna with uniform traveling-wave current distribution results in a lower profile, a more symmetrical circularly polarized radiation pattern, and a much better input impedance matching.