Low-profile dual-loop antennas with a straight wire for circular polarization

Using the method of moments, we analyze a novel dual-loop antenna backed by a conducting plane reflector. Special attention is paid to the bandwidth for a 3-dB axial-ratio criterion. First, a reference dual loop having a symmetric antenna configuration is investigated with a balanced feed. On the basis of the radiation characteristics, a dual loop having an asymmetric antenna configuration is designed. It is found that the bandwidth is twice as wide as that of the reference dual loop. Second, an asymmetric dual loop with an unbalanced feed is realized. Finally, a planar array of the two asymmetric dual loops with an unbalanced feed is constructed, and the radiation characteristics are demonstrated with experimental results.