Circularly Polarized Yagi-Uda Array Antenna with a One-Point-Opened Driven Loop

Abstract

This paper investigates the characteristics of a circularly polarized Yagi-Uda array. A one-point-fed circular wire loop with one open point is used as the driven element to launch circular polarization. Loops or crossed wires are used as parasitic elements. Standing wave current exists on one part of the driven loop and traveling wave current exists on the other. We found that circular polarization is produced by the rotation of these currents as a function of time. The design charts for the circumference of a 3-element Yagi-Uda loop array are calculated to obtain desired values for the axial ratio, the directional gain and the input impedance. The circumferences of the array are chosen from these charts. The array's characteristics are measured and then compared with the calculated results, which include the effects of a feed cable. An axial ratio of less than 0.1 dB and a directional gain of 9.6 dB are obtained for a 10-element Yagi-Uda loop array.