Meander-line-loaded circularly polarized square-slot antenna with inverted-L-shaped feed line for C-band applications

A compact broadband circularly polarized square-slot antenna based on an offset-fed inverted-L-shaped microstrip feed line is proposed. A rectangular slot beneath the feed line and an inverted-L-shaped grounded strip on the left bottom corner of the wide square slot produce dual-wideband circular polarization (CP) coverage in a compact size. Meander lines with a square slot loaded at the right bottom corner of the ground plane result in broadband CP through overlapping of the dual-wideband axial ratio (AR) bandwidths. The magnitude and phase differences between two field components can be controlled effectively with proper tuning of the square slot dimensions (4.5 x 4.5 mm(2)), which is helpful for broadening AR bandwidth over the C-band by minimizing AR values (<= 3 dB). The overall dimensions of the prototype are only 26 x 26 x 1.6 mm(3). The antenna prototype has been validated experimentally. The measured results indicate an impedance bandwidth of 104% (3.56-11.22 GHz) and a 3 dB AR bandwidth of 76% (3.90-8.72 GHz). A peak gain of 3.4-4.42 dBi is achieved within the AR bandwidth. The proposed antenna is suitable for CP applications in the C-band.