Design of bezel antennas for multiband MIMO terminals using Characteristic Modes

Designing decorrelated MIMO antennas in small mobile terminals at frequencies below 1 GHz is challenging since more than one antenna tend to excite the single resonant mode available to a typical chassis structure. This challenge increases even further when multiple frequency bands are required from each antenna. Recently, a design framework to obtain efficient and decorrelated MIMO antennas based on the Theory of Characteristic Modes was proposed. By slightly modifying the chassis, multiple orthogonal resonant modes may be created and excited to facilitate low correlation at frequencies below 1 GHz. In addition, multiband operation per antenna can be achieved by correlating the characteristic currents of different modes across different frequency bands. In this work, we apply the proposed framework to make opportunistic use of the bezel structure popular in mobile terminal designs to achieve efficient and uncorrelated multiband MIMO antennas.