Design of a dual-band dual-sense circularly polarized annular-ring slot antenna

This paper investigates an annular-ring slot antenna loaded by reactive components to generate dual-band dual-sense circular polarization. The antenna consists of two microstrip-line-fed and concentric annular-ring slots. Each annular-ring slot can obtain specific circularly polarized (CP) radiation through introducing an appropriate reactive component, i.e. distributed capacitor/inductor, at a preselected location. The design concept has been explained, which is validated by numerical analysis. The 3-dB axial ratio (AR) bandwidths of nearly 6.7% and 4.2% have been achieved, respectively, for the lower and upper bands.