Broadband Polarization-Reconfigurable Water Spiral Antenna of Low Profile

This letter presents a novel circularly polarized water spiral antenna with polarization reconfigurability and low profile. It is basically an Archimedean spiral antenna with two water arms and fed by a parallel stripline. A conducting plate is used as the reflecting plane for unidirectional radiation. A glass container with two water channels, the upper one for left-hand circular polarization and the lower one for right-hand circular polarization, is mounted above the reflecting plane. By controlling the water flow among the water channels, the polarization of the antenna can be switched. A prototype is fabricated and tested. Measured results show that the proposed antenna has an overall bandwidth (vertical bar S-11 vertical bar < -10 dB, AR < 3 dB) of 40% for the two polarization states.