Compact MIMO antenna with high port isolation for triple-band applications designed on a biomass material manufactured with coconut husk

A compact two-element multiple-input multiple-output (MIMO) antenna is proposed for triple-band applications with very high port isolation. The structure is constructed in-house with a flexible biomass material which is coconut husk. Two metallic "8"-shaped antenna structures are employed manually on the substrate to serve as MIMO elements. Frequency bands of the antenna for (S-11 <= -10 dB) are obtained from 2.04 to 2.51 GHz, 4.43 to 5.35 GHz, and 6.76 to 8.78 GHz. The antenna fulfills the wireless local area network (WLAN) (2.4-2.485/5.15-5.35 GHz), fixed-mobile (4.45-5.15 GHz), and International telecommunication union (ITU) (8-8.5 GHz) application bands. A stub with three sub-sections is integrated in the ground to improve the overall triple-band port isolation characteristics. It is found that the minimum port isolation for entire application bands is greater than 20 dB. This low correlation between the elements is further confirmed by low value of envelope correlation coefficient (ECC < 0.14) and high value of diversity gain (DG > 9.98 dB). Channel capacity loss (CCL < 0.22 bit/s/Hz) and mean effective gain (MEG = +/- 0.19 dB) are also found within acceptable ranges. Characterization of the substrate material of the proposed MIMO antenna is rigorously investigated by analyzing its dielectric constant and loss tangent. Simulated and measured results ratify that the antenna is fit for triple-band MIMO applications.