Compact Broadband Linearly Polarized Quincunx Metasurface Antennas Using Embedded Fractal Design

A quincunx metasurface (MTS) structure is presented and exploited to design compact broadband metasurface antennas (MTAs). The MTS patch unit is constructed by connecting five same-size quincunx-arrangement squares with strip lines. Since it is a fractal structure and structurally embedded with other units, the gap between adjacent units is prolonged, increasing the edge capacitance. Meanwhile, the surface current is adjusted to flow along the diagonal of quincunx patches, producing a large strip inductance. Hence, the resonance responding to the MTS radiator can be shifted to the low frequencies, while a compact radiating aperture can be obtained accordingly. With the help of characteristic mode analysis (CMA), the quincunx MTS array is modified for further miniaturization. Jerusalem cross aperture and four rectangle apertures are etched on the ground plane, generating aperture modes. Subsequently, the modified quincunx MTS is coupled to a U-shaped feeding network through apertures, forming a horizontally polarized MTA and realizing an operating bandwidth of 37.92% and a peak gain of 7.36 dBi with a compact radiating aperture of 0.34\lambda _{0} \times 0.34\lambda _{0} . Ultimately, a 45° linearly polarized quincunx MTA using a double U-shaped feeding network is also proposed, obtaining a broader operating bandwidth of 44.60% and 6.43 dBi peak gain with 0.34\lambda _{0} \times 0.34\lambda _{0} radiating aperture.