A Dual-Band Circularly Polarized Complementary Antenna

A dual-band circularly polarized complementary antenna loaded with adjusting stubs is presented. The antenna consists of a semi-circle shaped printed monopole fed by a 50- $\Omega$ microstrip and the complementary metal structure part connected to the ground plane. Due to the complement structure, this antenna can work in dual-band linearly. To achieve dual-band circular polarization, rectangular and L-shaped adjusting stubs are added. By adjusting the parasitic elements appropriately, the conventional complementary antenna can be converted into a dual band circularly polarized antenna. The antenna impedance bandwidths are 400 MHz centered at 2.5 GHz and 2000 MHz centered at 5.8 GHz. The 3-dB axial ratio (AR) bandwidths are 40 MHz centered at 2.41 GHz and 640 MHz centered at 5.38 GHz. The measured results agree well with the simulated results.