In this paper, a novel compact hexagonal shaped ultra-wideband multiple-input multiple-output (UWB-MIMO) Koch fractal antenna is designed with penta-band rejection characteristics for portable devices. The antenna rejects the C-band downlink frequency from 3.7-4 GHz, the C-band uplink frequency from 5.75-6.05 GHz and the satellite bands from 7.45 to 8.4 GHz. The band 7.45-7.55 GHz is used by the meteorological satellite service for the geostationary satellite services. The band 7.75-7.9 GHz is used by the meteorological satellite service for non-geostationary satellite services. The band 8.025-8.4 GHz is used by the Earth exploration satellites for geostationary satellite services. The C-band and satellite bands interfere with the UWB and have been rejected using a band reject filter. A spiral shaped slot is introduced inside the fractal hexagonal monopole to introduce band reject characteristics. The band suppression and widening of the impedance bandwidth are achieved by using defected ground structures. The antenna has wideband impedance matching with S11 < -10 dB in the UWB frequency range from 3.1 to 13.6 GHz and has a low mutual coupling with S21 < -19 dB. The antenna has very low envelope correlation coefficient of less than 0.17 and low capacity loss of 0.254, which proves that the MIMO antenna shows good diversity performance.
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