Wideband Tri-Polarization Reconfigurable Magneto-Electric Dipole Antenna

A wideband polarization reconfigurable magneto-electric (ME) dipole antenna is presented. The proposed ME dipole is able to work in three different polarization states including one linear polarization and two orthogonal circular polarizations. The linearly polarized operation mode is based on a Γ-probe-fed ME dipole of four-sectional structure. And perturbation is introduced by connecting the +45° (or -45°) diagonal parts of the four sections with a diode embedded line to realize circularly polarized (CP) radiation. A simple biasing network driven by one 1.5 V dc source is designed to manipulate the state of four p-i-n diodes and hence switch the polarization. The presented reconfigurable ME dipole demonstrates distinctive features such as stable gain, high front-to-back ratio, and symmetric radiation pattern. Furthermore, a wide effective bandwidth (BW) in terms of the overlapped frequency region within which the impedance BW (S₁₁ < -10 dB) for all polarization states and the axial ratio (AR) BW(AR < 3) for both CP states are sustained simultaneously is obtained. An antenna prototype based on the proposed design is fabricated and tested for verification. Measured results show an effective BW of 7.9% (with an overlapped impedance BW of 31% and overlapped AR BW of 7.9%), comparatively high gain of 9 ± 0.8 dBi, and high efficiency of 80%-90% for all polarizations across the operating band.