Design and Characterization of 10-Elements MIMO Antenna With Improved Isolation and Radiation Characteristics for mm-Wave 5G Applications

A ten-elements MIMO antenna with improved isolation and reduction of X-polar radiation (XPR) in millimeter (mm) wave region of n258 (24.25-27.5 GHz) is presented. The individual antenna element consists of stub loaded coplanar waveguide (CPW) structure with elliptical shaped radiator. Elliptical shaped Defected ground structure (DGS) has been incorporated at ground to reduce the mutual coupling effect between the adjacent antenna pairs and the minimum isolation obtained 35 dB. The backside of the substrate has a metallic plane with defects which is not connected to the coplanar ground of the antenna and it acts as a reflector to improve the radiation characteristics by lowering of XPR as well as improving the co-pol to X-pol isolation up to 20 dB and 28 dB in the boresight direction in both the XZ and YZ planes respectively. The diversity performances in terms of Envelope Correlation Coefficient (ECC), Diversity Gain (DG) and Channel Capacity Loss (CCL) are obtained as
$0.1\times 10^{-6}$
, 10 dB and 0.005 bps/Hz respectively which are within the acceptable limits. Mean effective gain (MEG) values with respect to the excited port 2 and port 3 is identical and approximately −3 dB and the multiplexing efficiency of the proposed MIMO antenna is satisfactory over the bandwidth. The group delay is investigated and found to be almost constant with a variation of 1.2 ns thus indicating linear phase characteristic of the antenna. The proposed structure is compared with other mm-wave MIMO antennas and found to be advantageous. A prototype of the proposed 10-elements MIMO is fabricated, and the measured results resemble with the simulated results.