Wideband Water Helical Antenna of Circular Polarization

Abstract

This paper describes a novel helical antenna made of pure water. The water helical antenna is realized by replacing the metallic arm of a conventional helical antenna with a plastic tube of circular cross section filled with pure water. The axially symmetric TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> mode is excited along the water arm and accounts for the wave propagation and radiation. Circular polarization (CP) is achieved by choosing a proper dimension of the water helix. The measured results show that the proposed water helical antenna has an overlapping impedance bandwidth (|S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB) and an axial ratio (AR) bandwidth from 1.27 to 2.13 GHz, or 50.6% fractional bandwidth. A water helix antenna with polarization reconfigurability is also designed and demonstrated. The measured results show that the proposed helix antenna exhibits polarization-reconfigurable capability over a wide frequency band.