Four-element quad-band multiple-input-multiple-output antenna employing split-ring resonator and inter-digital capacitor

In this study, a novel four-element multiple-input-multiple-output (MIMO) antenna having quad-band characteristics is proposed. A coplanar waveguide-fed monopole is loaded with a split-ring resonator and an inter-digital capacitor to achieve miniaturisation and quad-band operation. These quad-band elements are arranged properly to implement a four-element MIMO configuration which provides both spatial and pattern diversities. The achieved isolation performance is better than 20 dB. Measurement results confirm that the proposed MIMO antenna operates at 1.95, 2.39, 2.64 and 3.27 GHz with impedance bandwidths of 2.66, 6.57, 8.8 and 4.09%, respectively. The proposed antenna exhibits quasi-monopolar radiation pattern and measured envelope correlation coefficient <0.01 is obtained in all the operating bands. The proposed antenna can be useful for MIMO applications in global system of mobile/Bluetooth/wireless local area network/worldwide interoperability for microwave access operating bands.