Mitigation of mutual coupling in 2 × 2 dual slant polarized MIMO antennas using periodic array of SRRs loaded with transmission line for LTE band 40

摘要

2 × 2 dual slant polarized multiple input multiple output (MIMO) antennaswith reduced mutual coupling is presented for polarization and spatial diversity.The design of printed periodic array of split ring resonators (SRRs) loadedwith horizontal strip transmission line is proposed to mitigate the mutual couplingamong the MIMO antenna elements. An equivalent circuit model, characterizesthe effect of coupling between the array of SRRs and the loadedtransmission line, which together reduces the near field coupling between theadjacent antenna elements. The additional horizontal strip at the bottom is utilizedto seek the return current path to the ground plane. Polarization and spatialdiversity is achieved by utilizing dual slant 45~0 polarized antenna elementswith eight independent channels. All four dual polarized antenna elements aredesigned to operate with a VSWR of <2 for (2.3-2.4 GHz) Band 40. Dual slant45~0 polarization is achieved by utilizing two printed planar bow-tie antennasin orthogonal orientation. Measured and simulated results shows by incorporatingperiodic array of SRRs loaded with transmission line a considerablemutual coupling reduction of 25 to 50 dB is achieved in E-plane, H-plane, andD-plane over the required band 40. An isolation of 30 dB and an average gainof 7.5 dB is measured for dual slant 45~0 polarized antenna elements. MIMOperformance metrics in terms of envelope correlation coefficient and diversitygain are also investigated.