Bandwidth and gain improvement of a circularly polarized dual-rhombic loop antenna

We present a novel way to improve the performance of a circularly polarized (CP) dual-rhombic loop antenna. The bandwidth is enhanced by adding a pair of parasitic rhombic loops inside the dual-rhombic loop while the gain is increased with the help of a short backfire antenna (SBA). Good impedance matching is obtained by introducing a broadband balun. The addition of the parasitic elements leads to a bandwidth of 46% for $ axial ~ratio ~( AR) leq 2~ dB$ with an impedance bandwidth of 50% for $ VSWRleq 2$. The dual-rhombic loop excited SBA achieves an AR ( $leq 3~ dB$ ) bandwidth of 45% with an antenna gain of 11 dBi.