Frequency reconfigurable multiple-input multiple-output antenna with high isolation

A frequency reconfigurable multiple-input multiple-output (MIMO) antenna is presented. The proposed MIMO antenna consists of two reconfigurable printed monopole antennas with coupled conductors and an isolation improvement structure located between the two antennas. In order to change the operating frequency, PIN-diodes are embedded in the antennas. According to the on/off state of the PIN-diode, the resonant frequency is changed between the WLAN band (2400-2483 and 5150-5350-MHz) and the m-WiMAX band (3400-3600-MHz). The proposed isolation technique produces an S21 of less than -20-dB for both service bands. Simulation and measurement results confirm the antenna performance. Peak gains of 3.81-dBi at 2.4-GHz, 1.87-dBi at 5.2-GHz and 5.15-dBi at 3.5-GHz are found. Radiation efficiencies are greater than 58.85- over all of the operating frequency bands. The measured envelope correlation coefficient (ECC) and the mean effective gain (MEG) are suitable for use in MIMO antenna systems.