Low-Profile Wideband Conjoined Open-Slot Antennas Fed by Grounded Coplanar Waveguides for $4\times4\,\,5$ G MIMO Operation

Four grounded coplanar waveguide (GCPW)-fed open-slot antennas conjoined into a cross shape with a central circular slot are presented for 4 × 4 fifth-generation (5G) multiinput multi-output (MIMO) operation in 3.3-4.2 GHz. The four conjoined slot antennas have a 1 mm low profile (about 0.01λ at 3.3 GHz) and a compact size of 42 mm × 42 mm (about 0.46λ × 0.46λ at 3.3 GHz) to provide four wide operating bands (about 24% centered at 3.75 GHz) with antenna efficiency better than 40%. The conjoined circular slot leads to enhanced operating bandwidth of the four slot antennas and good decoupling thereof. Owing to the 1 mm low profile, the conjoined slot antennas are promising to be integrated within the dielectric back cover of the 5G terminal device, thereby decreasing the antennas' volume inside the device. Details of the GCPW-fed conjoined slot antennas for 5G-MIMO operation are presented.