Metamaterial circular spiral antennas

A single-arm circular spiral antenna with metamaterial properties in its arm is proposed. Taking into consideration the left-handed and right-handed property of metamaterials, it is predicted that this antenna will produce left-handed circularly polarized radiation and right-handed circularly polarized radiation at two different frequency bands. Moreover, circular configuration will yield in better impedance matching and axial ratio than its rectangular counterpart. Simulation results confirm with prediction with overlapping LHCP and RHCP bandwidth of 9.4% and 9.9% respectively and peak gains of 2.34 dBi and 7.27 dBi. A comparative study on the effect of reflectors on the performance of spiral antenna is also conducted. The reflectors include a PEC, PMC and HIS. It is predicted that when the spiral antenna is backed by the HIS reflector at a height of 0.04 times the wavelength of 7.5 GHz, a wide bandwidth with high unidirectional gain will be achieved as opposed to the other reflectors. Simulation results confirm the prediction with a 28% return loss bandwidth, 19% 3-dB axial ratio bandwidth and a 6dBi gain. Comparison with two other reflectors and without reflector is also provided.