UWB MIMO Slot Antenna with Minkowski Fractal Shaped Isolators for Isolation Enhancement

A novel compact ultra-wideband (UWB) multiple input multiple output (MIMO) slot antenna with band notch characteristics is presented for portable wireless UWB applications. The antenna comprises co-planar waveguide feed (CPW) and two radiating monopoles oriented in orthogonal orientation for providing orthogonal radiation patterns. A Minkowski fractal parasitic stub along with a Minkowski fractal grounded stub has been placed at 45 degrees between the monopoles to reduce the coupling between them which in turn establish high isolation between the radiators. An excellent band notch characteristic is obtained at 5.5 GHz by etching a modified E-shaped compact slot on the radiators. At the centre of notched band, the efficiency and gain of the antenna drop significantly which indicates a good interference suppression. Results show that the designed antenna meets -10 dB impedance bandwidth and -17 dB isolation throughout the entire operating band (3.1-12 GHz). Novelty of this design lies in improving isolation using compact fractal structures which occupy less space than conventional isolation mechanisms in MIMO structures. The simulated and measured results show that the proposed antenna is convenient for MIMO diversity systems.