Polarization-Reconfigurable and Frequency-Tunable Dipole Antenna Using Active AMC Structures

A polarization-reconfigurable and frequency-tunable mechanism based on an active artificial magnetic conductor (AMC) structure is proposed. The active AMC unit cell consists of a four-corner-cut inner patch and four triangles loaded with four varactors, and it can realize polarization-reconfigurable and frequency-tunable reflection characteristics by adjusting the capacitance of the varactors. By employing it as a ground plane of a pair of linearly-polarized dipole antennas, a multi-functional antenna can be well designed with polarization reconfigurability and frequency-tuning capability. By controlling the DC bias of the varactors accordingly, the three polarization states of right-/left-handed circular polarization (R/LHCP) and linear polarization (LP) can be switched, respectively, while the operating frequency of each polarization can be flexibly tuned. The measured tuning frequency ratio for the LP state (|S11