This paper introduces an innovative transparent, flexible, and fish-tail shaped antenna specifically tailored for ultra-wideband multiple-input multiple-output (MIMO) systems. The antenna, terephthalate (PET) substrate to enhance antenna radiation performance, transparency, and flexibility. We employ a fishtail radiator along with a hollow ground fed by coplanar waveguide (CPW) to realize broadband impedance matching. Additionally, by implementing a vertical arrangement of units and neutral line connections, we achieve notable isolation for
MIMO antennas in ultra-wideband scenarios. The fabricated MIMO antenna exhibits a minimum transparency of 71.1% and 85.9% with and without reflectors, respectively.
Measurement results confirm the antenna's operation within the 3-20 GHz frequency range, showcasing isolation levels surpassing 30 dB, a peak gain of 2 ± 2 dBi, and radiation efficiency ranging from 45 ± 5%. These findings underscore the suitability of the proposed antenna for ultra-wideband communication applications.