This article proposes a novel circularly polarized microstrip antenna supported with bidirectional opposite-sense radiation using a dual-layered arrow-shaped slot perturbation. Unlike a conventional perturbation which is etched only on one side, the arrow-shaped slot perturbation of the proposed antenna is divided into two diagonal half-arrows and etched on both the top and bottom side. Consequently, the counter-clockwise rotation of electric surface currents at the radiator side for right-handed circular polarization and the clockwise rotation of those at the ground side for left-handed circular polarization are successfully achieved. The measurement results of the proposed antenna show good agreement with the simulations of reflection coefficients, axial ratios, antenna gains, and radiation patterns.
