Compact antenna arrays for MIMO applications

We use antenna-antenna interactions to reduce spatial correlations among antenna elements. which allows for closely packed arrays for MIMO applications in small portable devices. The reduction in spatial correlations is a result of the modification of the antennas' radiation pattern when the elements are brought close to each other. We show how a particular dielectric antenna element can be manipulated so that closely placed elements have either nearly isotropic radiation patterns or more anisotropic ones. Accordingly, we find that in a multiple-scattering environment the correlation between antennas with isotropic pattern has an oscillatory behavior with period /spl sim//spl lambda/ expected for a 3D Rayleigh fading environment. On the other hand, antennas with an anisotropic pattern show a low degree of spatial correlation of /spl sim/0.2 independent of the antenna separation. Electromagnetic simulations confirm our experimental observation and provide a path for a systematic design and optimization of compact antenna arrays.