Dual-Loop Arrays Fed by Coplanar Parallel Lines for Wideband Circular Polarization

Using the method of moments, we analyze three types of series-fed array antennas for circular polarization. First, we present a reference antenna's radiation characteristics with symmetrical dual loops fed by balanced parallel lines. Next, we modify the symmetrical dual loops into asymmetrical ones to enhance a circularly polarized (CP) wave bandwidth. It is found that the modified antenna has a bandwidth of 35% for a 3 dB gain-drop criterion, where the axial ratio is less than 3 dB. Finally, we use unbalanced parallel lines for feeding the asymmetrical dual loops to simplify the feed system. It is revealed that the antenna shows a CP wave bandwidth of 19%, which is twice as wide as that of the reference antenna.

Automated summary

By utilizing the method of moments, three types of series-fed array antennas for circular polarization were analyzed. The modification of symmetrical dual loops to asymmetrical ones, along with the use of unbalanced parallel lines for feeding, successfully increased the bandwidth of circularly polarized waves.