Compact two-element UWB fractal monopole MIMO antenna using T-shaped reflecting stub for high isolation

Abstract

In this paper, a compact 2-element ultra wideband MIMO antenna system measuring 20×32 mm2 is proposed. The radiating element of the monopole antenna configuration is fractal shaped, and is fed by a coplanar waveguide independently. A T-shaped reflecting stub is placed between the two antennas to reduce mutual coupling and hence to improve isolation. The antenna performance is studied in terms of impedance matching, isolation, radiation pattern, and Envelope Correlation Coefficient (ECC). The measured result shows that the proposed antenna operates in the UWB frequency range of 3.1-7.5 GHz with S11 ≤ -10dB (S11 ≤ -8dB for 7.5-10.6 GHz) and S21 ≤ -15dB. The antenna exhibits an ECC of less than 0.06. The proposed antenna configuration provides beam tilting over the operating frequency due to the presence of the T-shaped stub, thus creating pattern diversity.