Asymmetrically printed low-profile artificial magnetic conductor 4-port circularly polarized MIMO antenna with bi-directional radiation modes for lower sub-6 GHz (n77/n78/n48) 5G NR bands

A printed low-profile Asymmetrical Artificial Magnetic Conductor (AAMC) with Circular Polarization (CP) characteristics is presented in this article. The desired asymmetrical arrangement offers inherent advantages of manipulating the electromagnetic waves of high impedance surfaces with bandwidth and radiation improvement characteristics reminiscent of standard AMC symmetric cells. Orthogonally rotational slotbased quarter mode stubs have been strategically used to develop a 4-port multipleinput multiple-output (MIMO) antenna that imitate bi-directional radiation modes (+Z : Left-hand circular polarization (LHCP) and -Z : Right-hand circular polarization (RHCP)). Additionally, the MIMO layout has been retained ground connected topology with no additive isolation network, ensuring an effective isolation response in the operational band and good 10-dB impedance response. Experimental validation has shown with a fabricated prototype MIMO antenna is capable of operating from(2.64 -4.28) GHz with a 10-dB impedance bandwidth of 47.4%, a 3-dB axial ratio (2.48 -4.76) GHz with 63% 3-dB ARBW, a peak gain of 5.6 dBic, and inter-element port isolation > 20 dB. Good polarimetric purity or effective polarization contrasts are illustrated by the bi-directional LHCP and RHCP radiation patterns, indicating effective far-field diversity parameters with low ECC < 0.01 and high DG ≈ 9.994 values. The proposed 4-port MIMO antenna's performance perspectives indicate its viability in lower Sub-6 GHz (n77/n78/n48) 5G NR frequency band applications.