Heptaband swastik arm antenna for MIMO applications

In this study, a two-element multiple-input-multiple-output (MIMO) antenna with heptaband characteristics is proposed. The total size of the proposed antenna is 82 x 40 x 0.8 mm(3). The geometry of the radiating element is derived from a hybrid Quadric-Koch island fractal for size miniaturisation. The antenna operates at the bands of 0.95-1.02 GHz (GSM 900), 1.73-1.79 GHz (GSM 1800), 2.68-2.85 GHz (LTE-A), 3.66-3.7 GHz [ultra-wideband (UWB)], 4.20-4.40 GHz (UWB), 5.50-5.65 GHz [worldwide interoperability for microwave access/high-performance radio local area network] and 5.93-6.13 GHz (UWB). The spacing between the two radiating elements is maintained at 5 mm. The proposed heptaband swastik arm MIMO antenna exhibits an S-11 <= -6 dB and S-21 <= -17 dB over the entire bands of operation. It provides high isolation without requiring any additional structures. The antenna also offers stable radiation characteristics with circular polarisation at the operating bands of 3.66-3.7 GHz and 5.93-6.13 GHz and linear polarisation at 0.95-1.02 GHz, 1.73-1.79 GHz, 2.68-2.85 GHz, 4.20-4.40 GHz and 5.50-5.65 GHz bands. The diversity performance of the antenna is studied in terms of the envelope correlation coefficient which is <0.05, and capacity loss which is <0.5 bits/s/Hz at all the operating frequencies, making it suitable for use in fifth generation communication systems incorporating the existing bands.