Omnidirectional Circularly Polarized Reconfigurable Antenna Using Endfire Elements Based on SIW

In this paper, an omnidirectional circularly polarized reconfigurable antenna has been designed. The antenna consists of five H-plane horn structures and five parallel strips. There are phase shift lines between the horn structures and parallel strips to achieve the circular polarization radiation. Several slots are etched on the parallel strips to solder the PIN diodes. Through controlling the on/off state of the diodes, the left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) antenna can be reconfigured. Finally, the both 3-dB VSWR bandwidths and 3-dB axial ratio bandwidths of the proposed antenna are about 2.9 % (2.42 ~ 2.49 GHz) for LHCP mode and RHCP mode. And the antenna has an omnidirectional pattern with the non-roundness of 1.12 dB in the horizontal plane at 2.45 GHz. With the omnidirectional and circularly polarized reconfigurable characteristics, the proposed antenna is a good candidate for the polarization diversity and wireless communication of unmanned aerial vehicles (UAVs).