Broadband Circularly Polarized Slot Antenna Array Using Sequentially Rotated Technique for $C$-Band Applications

This letter presents the investigation results on a novel circularly polarized square-slot antenna (CPSSA) array designed to operate at a frequency of 5.5 GHz. In order to realize the proposed antenna array, four miniature circular polarized square-slot antennas are used with L-shape grounded strips located at the slots' opposite corners to reduce cross polarization. The antenna is fed by symmetric coplanar waveguide. The CPSSA element achieves a bandwidth of 16.6% for an axial ratio <formula formulatype="inline"><tex Notation="TeX">$\leq 3~$</tex></formula>dB. The CPSSA's performance is further enhanced with the construction of a novel 2<formula formulatype="inline"><tex Notation="TeX">$\,\times\,$</tex> </formula>2 antenna array that is designed using sequentially rotated feed technique. The 3-dB axial ratio of the array extends to approximately 2 GHz with an impedance bandwidth of 31%. The CPSSA array was designed to operate over the frequency range between 4 and 6.825 GHz corresponding to an impedance bandwidth of 52% for <formula formulatype="inline"><tex Notation="TeX">${\rm VSWR}< 2$</tex></formula> (1.71:1). Acceptable agreement between the simulation and measured results validates the proposed design.