High-performance circularly polarized antenna array using metamaterial-line based feed network

This communication presents a 2x2 circularly polarized (CP) antenna array composed of H-shaped patches. The uniqueness of this CP array is its feeding network, where state-of-the art metamaterial transmission lines (MMLs) are built to obtain the required quadrature phases. Experimental results show that the feed network has excellent power distribution and progressive phases over a wide bandwidth. As a consequence, the MML-based array exhibits excellent performance, viz. 85% impedance bandwidth (SWR ≤ 2), 89% axial-ratio (3-dB) bandwidth, 80% efficiency at a center frequency of 2.5 GHz and 55% pattern bandwidth with a criterion of 8-dBic gain level. The axial-ratio bandwidth is validated with cross-polar discriminations obtained from radiation patterns.