Circularly Polarized Monopole L-Shaped Slot Antenna With Enhanced Axial-Ratio Bandwidth

A wideband circularly polarized antenna with L-shaped monopole slots and rotated parasitic patches has been proposed. The measured results show that the antenna has VSWR (<; 2) and axial-ratio (AR <; 3 dB) bandwidth of 64%. A novel wideband feeding structure has been used to excite the L-shaped slot and match the structure to 50-Ω impedance. The rotated parasitic patches are devised in the close proximity of slot to further enhance the circular polarization purity. Moreover, a Bazooka (sleeve) balun is used to eliminate the currents on the shield of coaxial feeding line and degrade AR. The antenna is relatively low-profile, low-cost, and easy to fabricate.