Impact of current localization on the performance of compact MIMO antennas

In this paper, we study the influence of current localization on the isolation between two antennas in a compact terminal setting. The two antennas are chosen to be a monopole and a PIFA. The degree of current localization is controlled by the permittivity value of the PIFA´s dielectric loading. Both lossless and lossy cases are simulated in order to ascertain the underlying performance impact from current localization and its potential use in real implementation. Our results show that significant isolation enhancement is achieved with more localized currents. Moreover, the technique improves the terminal´s diversity and capacity performance both at the center frequency and over a given bandwidth. In addition, PIFAs with dielectric loadings of higher permittivity values and more localized currents are physically smaller. Antenna prototypes are fabricated, and the measured results agree well with the simulated results.