A Design of Reconfigurable Patch Array Antenna with Dual Circular Polarizations

In this paper, we present a 2 x 2 microstrip array antenna with dual circular polarizations. To switch the polarization states, the radiating patch is fed by a branch-line coupler and two T-junction power dividers. The array antenna can be reconfigured to radiate electromagnetic waves with either the right-handed or left-handed circular polarizations by controlling the branch-line coupler. A prototype is fabricated with a 0.4 mm thick FR4 top layer for radiating elements and a 0.8 mm thick FR4 bottom layer for a feeding network with a 5 mm air gap between the two layers. Simulated and measured results are compared, which show good agreements. Also, the properties of the reconfigurable array antenna with dual circular polarizations and high radiation efficiency are demonstrated.