Polarization-Sense Reconfigurable Circular Polarized Antenna

A single fed circular polarized microstrip patch antenna excited through near field coupling is proposed. L-shape near-field feed line is used to feed the microstrip patch antenna as it is useful to control the direction of the current, and change the polarization sense of the circularly polarized wave. By using near field coupling technique, the size of the microstrip patch antenna is reduced to be less than a half-wavelength of the guided wave. Along with the size reduction, slits must be inserted into the antenna to achieve good axial ratio. Its length has been optimized numerically to generate axial ratio that cover 2.4 GHz ISM band. Experiment results shows that the proposed antenna possesses an axial ratio bandwidth of 4.1% and 10-dB return loss covers 2.35 to 2.54 GHz. The proposed antenna is eligible for a communication network that uses right- and left-handed circularly polarized wave spatially.