A Compact Koch Fractal UWB MIMO Antenna with WLAN Band-Rejection

In this letter, a compact octagonal shaped fractal ultrawideband multiple-input-multiple-output antenna is presented, and its characteristics are investigated. In order to achieve the desired miniaturization and wideband phenomena, self-similar and space filling properties of Koch fractal geometry are used in the antenna design. These fractal monopoles are placed orthogonal to each other for good isolation. Moreover, grounded stubs are used in the geometry to provide further improvement in the isolation. The band rejection phenomenon in wireless local area network band is achieved by etching a C-shaped slot from the monopole of the antenna. The proposed antenna has compact dimensions of 45mm × 45mm and exhibits quasi-omnidirectional radiation pattern. In addition, it shows an impedance bandwidth (S¹¹ < 10dB) from 2 to 10.6 GHz with isolation better than 17 dB over the entire ultra-wideband range. Diversity performance is also evaluated in terms of envelope correlation coefficient and capacity loss. The measured results show good agreement with the simulated ones.