Design and Evaluation of Full-Duplex Terminal Antennas in Realistic User Scenarios

In this letter, a two-port antenna system based on orthogonal excitation of the ground plane modes is presented for full-duplex (FD) mobile device applications. An antenna isolation method based on employing a balanced and unbalanced antenna is used to achieve a high level of antenna decoupling. Moreover, the theory of characteristic modes is used as a systematic tool to analyze the orthogonal modal behavior of the antenna system. A prototype consisting of a balanced dipole antenna and a monopole antenna on a 120 × 55-mm² chassis is fabricated and measured. The measurement results verify the simulation results and show a high isolation value of 40 dB between the ports in free space. Furthermore, to evaluate the antenna system performance in realistic scenarios, the prototype was measured in three different user scenarios. The isolation level between the ports in user scenarios varies from 42 to 33 dB in the worst scenario. The proposed design can be applied in an FD system to suppress the self-interference as the first stage of interference cancelation.