A Compact Broadband Cross-Shaped Circularly Polarized Planar Monopole Antenna With a Ground Plane Extension

This letter presents a new broadband circularly polarized (CP) planar monopole antenna with a simple structure and compact size. Broadband CP operation is achieved by vertically extending one side of the ground plane, while a cross-shaped monopole structure and the presence of a slot in the ground plane assure a broad impedance bandwidth. The antenna is successfully simulated, and a prototype is fabricated. Measurement results indicate that the 3 dB axial-ratio bandwidth is about 42.6% (2.6 GHz, 4.8-7.4 GHz), fully covered by a -10 dB impedance bandwidth of 55.5% (3.35 GHz, 4.36-7.71 GHz). Furthermore, the proposed antenna can be used together with a metallic reflector to obtain directive radiation patterns with enhanced broadside gain.