A New Broadband Circularly Polarized Monopole Antenna With Modified Ground

This letter presents a new broadband circularly polarized (CP) monopole antenna with modified ground. The proposed antenna fed by coaxial probe consists of a square ground loaded with an L-shaped branch, which is capable of generating broadband CP radiation. In addition, an I-shaped slit is embedded into the ground plane to improve the impedance matching. The presented antenna has a 10 dB return loss bandwidth from 1.82 to 4.21 GHz (79.3% centered at 3.02 GHz), and a wide 3 dB axial-ratio (AR) bandwidth from 1.84 to 3.95 GHz (72.9% centered at 2.89 GHz). The measured gains are greater than 2.0 dBic in the AR band, and the gain variation within the AR band is less than 1 dBic, which means a good flat gain feature in the broad frequency band. Both the simulated and measured results validate the proposed design.