Metaspiral antenna system

A metaspiral has a negative phase constant within a specific frequency band and a positive phase constant within a different frequency band. The circularly polarized (CP) beams radiated within these different bands have different gains. It is found that placing a dielectric plate above the metaspiral contributes to yielding a desirable situation where the gains for left-handed and right-handed CP waves are almost the same. It is also found that the input impedance is not deteriorated by the presence of the dielectric plate. The effects of removing the inner part of the dielectric plate on the antenna characteristics are also discussed.