Polarization Agile Circular Wire Loop Antenna

In this letter, we show that the inclusion of a pin diode suitably positioned in a circular wire-loop antenna mounted over a ground plane can be used to electronically control the polarization radiation properties of the antenna. Specifically, we use a gapped circular wire loop of circumference 1.13 lambda(c) at 1 GHz positioned 0.3 lambda(o) above a 33 cm x 33 cm ground plane. Inclusion of a pin diode into a 2.7-mm gap, suitably positioned with respect to the generator, allows the antenna current distribution to be electronically controlled such that the loop produces linearly polarized radiation VSWR of 1.8 or circularly polarized radiation VSWR of 2.5, boresight axial ratio less than 2.5 dB.