Very-Low-Profile, Dual-Polarized Oblong Loop

A two-port, oblong loop antenna producing two orthogonal waves for fifth-generation (5G) operation in the 3.4–3.6 GHz band with transmission coefficient (S
12
) < −32 dB and excellent envelope correlation coefficient (ECC) < 0.002 is introduced. Unlike the conventional, probe-fed, dual-polarized patch antennas, the proposed design uses the loop antenna fed by the coaxial cables and has a coplanar structure. The loop antenna is placed 1 mm above the top edge of the display, has a compact size of 30 mm x 4 mm and two feed ports spaced merely 2 mm (about 0.02-λ at 3.4 GHz) apart. Port1 is designed as coupling feed to the loop while port2 is a direct feed in the loop, all located along the loop's central line. With this feeding arrangement, port2 is located in the current-null region when port1 is excited, whereas maximum currents of port1 excitation are located in the current nulls of port2 excitation. These properties lead to two decoupled, orthogonal radiating waves with very low ECC. Additionally, due to the oblong structure of the loop, pattern diversity is also achieved.