Slotted patch antennas with wide axial ratio beamwidth for passive keyless entry system

The design of circularly polarized microstrip patch antenna (MPA) with wide axial ratio beamwidth working at 2.4GHz band is proposed. The wide axial ratio beamwidth is achieved by a 45° rotated slot cut in the center of the square MPA. By placing two back-to-back MPAs on intelligent door lock, the function of indoor-outdoor recognition has been successfully realized.