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A Novel Microstrip-CPW Fed Planar Slot Antenna With Broadband and Circular Polarization

A novel broadband circularly polarized planar slot antenna with microstrip-CPW fed is proposed in this paper. It consists of a wide rectangular slot and a coplanar waveguide (CPW) feedline, both etched on the ground plane of a dielectric substrate, as well as a microstrip to CPW transition on the reverse plane of the substrate. The microstrip-CPW feed structure is appropriately designed so that the even and odd modes of the CPW are excited with 90° phase difference, and are then fed to the slot antenna to realize wideband circular polarization operation. The mechanism of circular polarization in this design is explained and the detailed parametric study of the antenna is carried out. The measured 3-dB axial-ratio bandwidth is 39.4% (1.98 ~ 2.95 GHz), and -10 dB reflection coefficient bandwidth is 57% (1.73 ~ 3.11 GHz).