A reconfigurablecircularly polarized antenna is proposed and developed in this letter. Theproposed circularly polarized antenna consists of two linearly polarizedinverted-L antenna elements with double-folded arms. To improve impedancematching and radiation characteristics the double-folded structure plays asignificant role. Circular polarization is achieved by properly adjusting thelengths of two arms, quadrature currents can be produced on two orthogonalelements. The proposed linearly polarized antenna elements are low-profile andsmall in size, the proposed circularly polarized antenna is about 34.5mm inlateral size and 18mm in height. The feeding configuration is simplified byusing coaxial probe instead of an external polarizer. Better values areobtained between the simulated and measured results, which validate our designconcept.
The measured results show that the circularly polarized antenna has awide impedance bandwidth of 6% and a 3-dB axial ratio (AR) bandwidth of 1.16%. Index Terms—Circularlypolarized antenna, double folded arm antenna, inverted-L antenna. The circular polarization provides reduction inmultipath effect and flexibility in the orientation angle between a transmitterand a receiver hence CIRCULARLYpolarized (CP) antennas are compatible for radar tracking, global positioningsystem, satellite communication, radio frequency identification, and sensorsystems. various CIRCULARLYpolarized antennas with compact size have been developed for portable andmobile terminal applications In recent years.
Most of them are circularly polarizedmicrostrip antennas (CPMAs) with high-dielectric material substrate owing totheir low profile, easy manufacture, and light weight. Slotted andfolded patch structures are also introduced to construct small CPMAs. However,their main disadvantages are extremely narrow bandwidth and decreased radiationefficiency 1–5.