Ultra-wideband Circularly Polarized Wide-slot Antenna Fed by Three-stub Hybrid Coupler

In this paper, a three-stub hybrid coupler fed circularly polarized wide-slot antenna is presented and studied for ultra-wideband (UWB) applications. The proposed antenna is composed of a pair of orthogonally positioned radiating slots and a three-stub hybrid coupler which is used as the feeding network to excite the orthogonal slots in quadrature phase. The antenna is investigated experimentally in frequency domain in terms of impedance matching, gain, axial ratio, radiation patterns, and group delay, as well as in time domain in terms of pulse waveform and fidelity. The results show that the proposed antenna features desirable performance over 2.8-5.2 GHz, which is in particular suitable for lower UWB band (3.1-5.0 GHz) applications.