Polarization-Agile Circular Polarized Antenna Based on Proximity Feeding Technique

In this letter, the design and experimental validation of polarization-agile circular polarized antenna are presented. The antenna is comprised of a patch antenna with truncated slits and two proximity feedlines. The antenna produces a vertical linear polarized wave when it is fed by a proximity feedline. Horizontal linear polarized wave is then generated by applying a potential difference between two proximity feedlines. The quadrature phase difference between two orthogonal polarized waves is created by adding truncated slits into the patch antenna. By swapping the polarity of the proximity feedlines, polarization sense can be changed. The distributed circuit model is presented to describe the working mechanism of the antenna. Patch antenna with circular polarization agility is then validated through passive-type and active-type switching circuits. The measured axial ratio bandwidth is 4.085% (100 MHz), and the fractional impedance bandwidth is greater than 7% for the left-handed and right-handed circular polarized radiations.