Planar Antenna with Combined Structure of Annular Slot Array and Patch for Improvement of Radiation Efficiency

In this paper, a novel planar antenna with combined annular leaky-wave structure and patch is proposed for improvement of radiation efficiency. The antenna is constructed by a circle of slots with constant interval outside and a patch antenna in the center. The residual energy after the radiation of slot array is fed to the patch antenna again, so the more input energy can be radiated. Therefore, the radiation efficiency of this combined structure antenna is significantly improved compared with that obtained by the planar annular leaky-wave antenna only. The simulation results show that the radiation efficiency of this antenna is improved from 33.2% to 53.6%, and the variation of gain around the beam axis (in the conical surface of
$\theta=31^{\circ}$
) is within 3 dB.