Wideband Horizontally Polarized Omnidirectional Cylindrical Dielectric Resonator Antenna for Polarization Reconfigurable Design

Abstract

A compact horizontally polarized omnidirectional cylindrical dielectric resonator antenna (DRA) excited in the TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{011+\delta }$ </tex-math></inline-formula> mode is presented. It deploys a planar feed which comprises a cross-shaped feed line, four coupled strips, and four curved arms with end-shorted stubs. The TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{011+\delta }$ </tex-math></inline-formula> mode of the DRA is excited by the curved arms. Its intrinsically narrow impedance bandwidth is enhanced by using the coupled strips, and the cross-polar field is suppressed by the end-shorted stubs. The antenna has a measured −10 dB impedance bandwidth of 18.1%, which is much wider than the conventional bandwidths of 4.5%–7.4%. Its cross-polar level is lower than the co-polar level by 15 dB. This basic DRA is used to design the first polarization reconfigurable omnidirectional DRA with diodes. By controlling the states of the diodes, the DRA can be switched between TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{011+\delta }$ </tex-math></inline-formula> and TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{01\delta }$ </tex-math></inline-formula> modes to obtain horizontal and vertical polarizations, respectively. To verify the idea, a prototype was fabricated and tested. Reasonable agreement between the measured and simulated results is obtained. The measured impedance bandwidths of the TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{011+\delta }$ </tex-math></inline-formula> and TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{01\delta }$ </tex-math></inline-formula> modes are 16.8% (2.18–2.58 GHz) and 16.0% (2.25–2.64 GHz), respectively. The antenna has stable omnidirectional radiation patterns in both states