The performance of an antenna cancellation technique for a multipleinput-multiple-output (MIMO) full-duplex system that is based on null-steering beamforming and antenna polarisation diversity is investigated. A practical implementation of a symmetric antenna topology comprising three dual-polarised patch antennas operating at 2.4 GHz is described. The measurement results show an average of 60 dB self-interference cancellation over 200 MHz bandwidth. Moreover, a decoupling level of up to 22 dB is achieved for MIMO multiplexing using antenna polarisation diversity. The performance evaluation of the proposed technique was performed by simulation and measurement and the results have good agreement.

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 dualelement 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. The user caused changes in the antennas radiation patterns reduce the correlation in the lower band which enhance the diversity gain and multiplexing efficiency. The exposure of the hand in each scenario is studied by the Specific Absorption Ratio (SAR).

The paper presents an antenna system with combined full-duplex and 2-order multiple-input-multiple-output (MIMO) functionalities, i.e., a system capable of spatially multiplexing and spatially demultiplexing 2 datastreams in the same frequency and in the same time. By exploiting symmetries in the construct and the feed, simple corrective beamforming weights can be applied at the transmitter (Tx) ports in order to selectively cancel the Tx signal at the receiver (Rx) ports, thus guaranteeing a large amount of isolation necessary for fullduplex (i.e., simultaneous and in-band Tx and Rx) operation. On the other hand, the 2 MIMO ports (either at the Tx or at the Rx) are sufficiently decoupled thanks to polarization diversity. The proposed antenna system exhibits a remarkable level of fullduplex isolation over a wide bandwidth while maintaining low coupling between its MIMO ports and can serve as a concrete implementation of an antenna system equipped with both MIMO as well as full-duplex capabilities.

With the future long term evolution (LTE) auction for television white spaces at 600 MHz, there is a strong need for efficient handset antennas operating at very low frequencies. This communication shows a tunable antenna covering the LTE bands from 600 MHz to 2.6 GHz. The antenna uses state-of-the-art microelectromechanical system tunable capacitors in order to reconfigure its operating frequency. In this communication, the design mitigates the tuning loss with a tunable extended ground plane. The resulting dual-resonant antenna exhibits a peak total efficiency of −3.9 dB at 600 MHz.

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