Circularly polarized broadband antenna with circular slot on circular ground-plane

A novel circularly polarized antenna with a circular radiating aperture and circular ground plane for broadband characteristics is presented in this paper. The vertical and horizontal components of the L-shaped probe are separated and placed at the front and back sides of the substrate. The antenna is excited by a microstrip line which is connected to the vertical component of the L-shaped probe and electromagnetically couples the signal to the horizontal component of the L-shaped probe. The concept of placing an appropriate stub in the slot, by observing the electric field vector behaviour in the slot, is proposed to enhance the axial ratio (AR) bandwidth by around 15%. The fabricated antenna shows wideband impedance and circular polarization characteristics of 48% along with a maximum gain of 6 dBic. The measured and simulated antenna characteristics are in good agreement.