Linearly Polarized and Circularly Polarized Wideband Dipole Antennas With Reconfigurable Beam Direction

Abstract

Linearly polarized (LP) and circularly polarized (CP) dipole antennas with switchable beams are presented. The beam-switchable reconfigurability is realized by electronically controlling the state of switches on the side apertures of a square substrate integrated waveguide (SIW). Four wide dipoles are loaded in front of the four apertures. To generate one desired unidirectional radiation beam, the corresponding aperture is switched ON, which excites the corresponding dipole. Meanwhile, the other three apertures are switched off and perform as electric walls in the SIW. In this way, the other three dipoles work as reflectors of the excited dipole. Wide bandwidths and good directional radiation patterns can be obtained. Two fully functional LP and CP antenna prototypes with more than 47% bandwidths are developed and tested. The measurement result demonstrates antennas with measured gains of approximately 4.5 dBi and radiation efficiencies of approximately 80% over the operating band. Owing to the symmetrical antenna structures, the two designs are capable of switching the radiation beam at every 90° in the azimuth plane with identical patterns. In addition, the proposed designs possess compact antenna sizes, i.e., $0.51\lambda _{0}\times 0.51\lambda _{0}\times 0.39\lambda _{0}$ for the LP antenna and $0.95\lambda _{0}\times 0.95\lambda _{0}\times 0.46\lambda _{0}$ for the CP antenna, where $\lambda _{0}$ represents the free-space wavelength at the center frequency of 2.2 GHz.