Wideband Vertically Polarized Endfire Metasurface Antenna Fed by Tightly Coupled Monopole Probe Array

In this article, we proposed a wideband and vertically polarized endfire 2-D tapered metasurface (MS) antenna, which is fed by a tightly coupled monopole probe array (TCMPA). The TCMPA is a configuration consisting of a top-loaded short vertical monopole within a printed circuit board (PCB) stack between two ground planes. When appropriately designed, it exhibits a wideband characteristic by exploiting the operation principle of the tightly coupled dipole array (TCDA), which is well-suited for thin aperture-sized fifth-generation (5G) millimeter-wave (mmWave) antennas. In addition, the MS-based radiating structure was investigated through a dispersion diagram, which is imperative for impedance matching to the thin TCMPA in a PCB stack. A wideband operation of the TCMPA with the MS was demonstrated. A significant advantage of this is that the wideband operation of a very thin endfire antenna can be achieved using only a PCB: it was shown that the thickness of the proposed array is
$0.06\lambda $
low at the lowest operating frequency. The impedance matching bandwidth of
$1\times4$
array is 22.5–42.1 GHz (60.7%) for uniform excitation and 24.3–42.1 GHz (53.6%) for a scan angle of 45°. Experimental results, including total active reflection coefficient (TARC), realized array gain, and radiation pattern, were compared with simulated results, which were in good agreement. Finally, the comparative advantages of the proposed array were demonstrated compared to state-of-the-art 5G endfire linear array antennas.