Novel planar reconfigurable circularly polarized complementary antenna for unidirectional end‐fire radiation

Abstract

In this article, a novel planar reconfigurable circular polarization (CP) complementary antenna for unidirectional end-fire radiation is proposed. Its radiator is the combination of a shorted quarter wavelength patch and an electric dipole, which provide the vertical and horizontal polarizations, respectively. By adding a 90° phase delay line, the proposed antenna radiates CP electromagnetic waves in the unidirectional end-fire direction. Four p-i-n diodes are also inserted at joints of the electric dipole and the phase delay lines, and two orthogonal CP states, left-hand (LH) and right-hand (RH) CPs, can be switched. In order to reduce the number of DC bias lines, electric dipole arms on both sides of the substrate are connected by metal via-holes, which simplifies the DC bias lines. The proposed antenna at 2.45 GHz is designed and fabricated. Its measured impedance bandwidth with |S11| < −10 dB and 3-dB axial ratio bandwidth are 2.1% and 10.7%, respectively. Additionally, its maximum half power beamwidth in xoz plane is 196°. Reasonable agreement between the measured and simulated results validates the polarization reconfigurability of the proposed antenna.