Design of a Quad-Polarization-Agile Antenna Using a Switchable Impedance Converter

This letter presents a novel quad-polarization-agile aperture-coupled antenna using a reconfigurable impedance converter. The designed reconfigurable converter can achieve impedance and phase changes under the control of p-i-n diodes. Based on this converter, a quad-mode switchable feeding network can be produced. Utilizing the feeding network to excite a dual-polarized aperture-coupled patch antenna, polarization reconfigurability is realized. By switching the p-i-n diodes, two orthogonal linear polarizations (LPs) and two orthogonal circular polarizations can be generated. Measurement results show that its return-loss bandwidth is wider than 2.5% at LP modes, its axial-ratio bandwidth is better than 1.8%, and its cross polarizations are below -20 dB for all the states.