A compact 30×30 mm2 high performance four elements ultra-wide band multi-input multi-output (UWB MIMO) diversity antenna is proposed. The prototype antenna consists of four symmetrical antenna elements which are orthogonally placed on top surface of the substrate with partial slotted ground plane. The isolationamong the antenna elements is improved by placing antenna elements orthogonally without any additional decoupling structure. The various antenna characteristic parameters, i.e. return loss (< -10 dB), isolation parameter (<-22 dB), radiation patterns near omnidirectional, and maximum realized gain 4.8 dB, were measured. The MIMO performances of prototype antenna were also measured in terms of various MIMO diversity parameters and found ECC<0.06, DG>9.98 dB, TARC<-10 dB and MEG<-3 dB throughout the frequency band. This design provides an operational bandwidth from 2.15 to 16.75 GHz which covers the whole UWB spectrum and is suitable for portable devices.
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