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This study aims to propose a two-element multi-input-multi-output (MIMO) antenna for cognitive radio MIMO applications to avoid the complexities involved in reconfigurable antennas and improve the spectrum utilization efficiency.

The proposed MIMO antenna system comprises a wideband antenna that operates at 2 GHz–12 GHz for sensing the spectrum and four pairs of antennas for communication, which are single and dual-band antennas. Each pair of antennas meant for communication consists of two similar antennas. Moreover, the antennas meant for communication cover 93% of the bandwidth of the sensing antenna.

The first pair of antennas accessible at ports P2 and P6 and the second pair of antennas accessible at ports P4 and P8, which are dual-band antennas, operate at 3.05 GHz–3.85 GHz, 5.8 GHz–8 GHz and 2.05 GHz–2.55 GHz, 4.7 GHz–6.1 GHz, respectively. While the third pair of antennas accessible at ports P3 and P7 and the fourth pair of antennas accessible at ports P5 and P9 are single-band antennas and operate at 3.85 GHz–4.7 GHz and 8 GHz–11 GHz, respectively. Minimum isolations of 20 dB and 15 dB are attained between every two similar antennas for communication and between the sensing antenna and the antennas meant for communication, respectively. The correctness of the proposed antenna is verified with a fine match between the results obtained from simulations and measurements.

The proposed MIMO antenna possesses salient features, such as polarization diversity and performing a maximum of four communication tasks when all the white spaces are detected.