A broadband CPW-fed dual circularly polarized slot antenna with modified L-shaped monopoles

In this letter, a novel broadband dual circularly polarized (CP) square slot antenna based on coplanar waveguide (CPW) feed is presented. Two orthogonal modified L-shaped monopoles fed by the CPW structure are designed to achieve dual circularly polarization. Through digging several rectangular notches while adding extra needle shaped tuning strip between two monopoles, wide impedance bandwidth (IMBW), wide axial ratio bandwidth (ARBW) and high port isolation are realized. Finally, in order to verify the analysis, a prototype is fabricated and measured. The measured available -10 dB IMBW of each port is 76% (from 1.8 GHz to 4.0 GHz), which covers the whole 3 dB ARBW of 67% (from 1.87 GHz to 3.75 GHz). Besides, the port isolation is below -25 dB and the cross polarization level is over -15 dB across the entire operating band, which proves the proposed antenna a good candidate for communication systems.