Circular Loop Antennas with Quasi-Two Sources for Broadband Circular Polarization

Three loop antennas are analyzed using the moment method for an increase in a 3 dB axial ratio bandwidth. Each antenna is excited with a branched feedline vertical to the ground plane. First, circular and square (reference) loop antennas are investigated to compare the radiation characteristics. It is found that the present and reference antennas have axial ratio bandwidths of 17% and 12%, respectively. Subsequently, the present wire loop is replaced with a plate one. It is revealed that the plate-loop antenna shows an axial ratio bandwidth of 28%, wider than the reference antenna by a factor of two.