Experimental investigation on the effect of user's hand proximity on a compact ultrawideband MIMO antenna array

An experimental study of the interaction between user's hand and an ultrawideband multiple-input multiple-output (MIMO) antenna array is presented for mobile terminals. The dual-element array covers the frequency ranges 698–990 MHz and 1710–5530 MHz with a good efficiency in free space. Depending on the standard, it can be used for channel sensing in cognitive radio networks or for communications in cellular networks. Hand phantoms for three usage scenarios are used for the investigation, namely, personal digital assistant (PDA) right hand, PDA left hand, and two hands. The absorption in the immediate located hand is the main factor causing degradation of the total efficiency (slightly affected by the hand induced changes in the S-parameters), reduction and imbalance in the antennas mean effective gain contributing to a deteriorated diversity gain (DG). The user caused changes in the antennas radiation patterns reduce the correlation in the lower band which enhance the DG and multiplexing efficiency. The exposure of the hand in each scenario is studied by the specific absorption ratio.