A High-Efficiency Electrically Reconfigurable Circular Polarizer and Its Array Application

A novel electrically reconfigurable circular polarizer with high efficiency is proposed in this letter. The combination of a linearly polarized antenna and a metal strip inclined at a certain angle could achieve circularly polarized radiation. Therefore, the polarization of the antenna can be changed by controlling the metal strip. The proposed circular polarizer structure is simple, which is realized by two crossed dipoles printed on the top and bottom of the printed circuit board (PCB), respectively. A microstrip coupled slot antenna is used to feed the polarizer. By controlling the PIN diode in the middle of the dipole, switching between two circular polarizations is realized. Based on the proposed antenna element, a 2×2 antenna array is implemented with a sequentially rotated feeding network. With the difference in the feeding phase, the radiation beam of the array can be changed while switching the polarization state. Measured results show that the antenna element achieves a peak gain of 6.4 dBic with an overall axial ratio (AR) bandwidth of 2.44–2.5 GHz for both right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) with radiation efficiency of about −1 dB. The antenna array achieves 7.5 dBic (RHCP) and 10.8 dBic peak gains in the two pattern diversity states. The AR bandwidth of the array can cover the range from 2.28 to 2.5GHz. The proposed antenna features high efficiency, electronically reconfigurable polarization, and low cost, which is well suited for base station applications.