Broadband Circularly Polarized Slot Antenna Array Fed by Asymmetric CPW for C-Band Applications

ABSTRACT In this manuscript, a new design of broadband circularly polarized (CP) array antenna is presented. A 2 × 2 planar array antenna is accomplished using the proposed CP diamond-shaped slot element with an L-shaped patch. The feed network employs a 180-degree rat-race hybrid coupler to realize a −3 dB power split, equal in magnitude, 180-degree difference in phase. Two branch-line couplers then divide the signal energy into two paths and give the signal to each of the output branches with the same amplitude, but phase-shifted by 90 degrees, wherein the relative phases at four feed points are 0, 90, 180, and 270 degrees. The final dimensions of the 2 × 2 element array are 112 × 97 × 0.8 mm3. The simulated result shows that the impedance bandwidth for a voltage standing wave ratio (VSWR) < 2 is around 39.86% (4.78–7.16 GHz), and the 3-dB simulated AR (axial ratio) bandwidth is about 24.2% (4.83–6.16 GHz), and the antenna has a peak gain of 7.69 dBi over the bandwidth.