Non-Uniform Metasurface-Integrated Circularly Polarized End-Fire Dipole Array Antenna

This paper presents a high-gain wideband circularly polarized antenna composed of an end-fire dipole array antenna integrated with a metasurface. The antenna consists of a two-layer cascaded non-uniform metasurface made up of 4 x 4 circular patches with cross-slots of unequal lengths placed above an end-fire dipole array antenna with an air gap between the structures. The end-fire dipole array antenna comprises four equally spaced dipole elements, and each dipole is connected to a parallel stripline printed on the front and back sides of the substrate. The metasurface, which is made up of a circular patch with 2 x 2 center patches that have a different radius than the outer patches, and the cross-slots of unequal lengths are used for the polarization conversion of a linearly polarized wave to a circularly polarized wave. The measured reflection coefficients for |S11| <-10 dB yielded an impedance bandwidth of 25.6-31.8 GHz (21.5%), a 3-dB axial ratio (AR) bandwidth of 26.1-30.5 GHz (15.5%), a 3-dB gain bandwidth of 26.0-31.1 GHz (17.4%) with a peak gain of 11.0 dBic, and a radiation efficiency of more than 80% in the axial ratio bandwidth.