MIMO antenna with improved isolation for 5G millimeter wave applications

Abstract In this research, an 8-element multi-input multi-output (MIMO) antenna is presented for millimeter wave communication systems. The present design incorporates two circular rings cojoined with a monopole. Both the rings are cross-coupled for better radiation and less interference properties. The present MIMO structure is designed from the reference antenna by placing antenna elements along X and Y axis. The overall dimensions of the presented MIMO structure are <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>50</mml:mn> <mml:mspace width="0.14em"/> <mml:mi mathvariant="normal">mm</mml:mi> <mml:mo>×</mml:mo> <mml:mn>70</mml:mn> <mml:mspace width="0.14em"/> <mml:mi mathvariant="normal">mm</mml:mi> <mml:mo>×</mml:mo> <mml:mn>1.6</mml:mn> <mml:mspace width="0.14em"/> <mml:mi mathvariant="normal">mm</mml:mi> </mml:math> . The bandwidth of the proposed antenna ranges from 25.4 to 29.5 GHz, which covers the mm-wave frequency spectrum of n257 and n261 bands. The present MIMO antenna is a self-isolated MIMO antenna and provides the isolation of better than −27 dB which is desirable for the MIMO communication systems. To evaluate the diversity characteristics different parameters are examined like total active reflection coefficient (TARC), channel capacity loss (CCL), envelope correlation coefficient (ECC), and Diversity gain (DG). ECC of &lt; .003, DG &gt; 9.9999, TARC &lt; −19.8 dB at 28 GHz, and CCL less than 0.4 is obtained for the proposed MIMO structure in the specified frequency range. With the acceptable radiation pattern, the gain achieved by this antenna is 6.6 dBi at 28 GHz. The proposed structure is fabricated and it is found that the Simulated and measured results agree closely.