Low-Profile Circularly Polarized Staircase Curl Antenna Array With 2:1 Impedance and 50% AR Bandwidths for 5G mmW Communications

In this communication, a low-profile circularly polarized (CP) staircase curl antenna array with 2:1 impedance bandwidth and 50% axial ratio (AR) bandwidth is proposed for fifth-generation (5G) millimeter-wave (mmW) communications. It overcomes a vital drawback of complex multilayer structure of the wideband CP antenna array. By fully taking advantage of 3-D staircase layout, the curl element achieves 2:1 impedance bandwidth, 57.9% AR bandwidth, and a maximum gain of 7.4 dBic. Accordingly, benefiting from the tapered matching transformer, a single-layer full-corporate microstrip feeding network with 111.4% impedance bandwidth is constructed. For demonstration, an
$8\times8$
staircase curl antenna array is designed on three-layer PCB laminates. The proposed antenna array is measured with an impedance bandwidth of 76.9% (20.0–45.0 GHz) and an AR bandwidth of 53.6% (23.1–40.0 GHz), demonstrating a promising candidate to be used in 5G mmW communications.