The Effect of Antenna Physics on Fading Correlation and the Capacity of Multielement Antenna Systems

In this paper, we investigate the effects of antenna directivity and antenna orientation on fading correlation and, therefore, the channel capacity in multiple-input-multiple-output communication systems by means of a spherical simulation model. The correlation is caused by the mutual interaction of the scattering environment and antenna elements. To study the effect of antenna directivity and orientations on the correlation and channel capacity in a more realistic environment, we extend the ldquoone-ringrdquo model to a spherical scattering environment, which is appropriate for narrowband 3D Rayleigh fading. In our model, scatterers around a subscriber unit are distributed over a sphere centered on the antenna array in the subscriber unit. Antenna directivity is included in a precise way, and the antenna array can be placed in any orientation. Any type of antenna can be studied in the model. Through simulation, we find that directive antenna elements in linear broadside arrays make the channel capacity more strongly directive than when antenna elements are isotropic. Moreover, different antenna patterns and orientations have different outage capacities depending on the interaction of antenna directivities and the incident waves, which shows that the antenna pattern and orientation affect the channel capacity to some extent. In the uniformly scatter-rich environment, the microstrip antenna array can have 10% higher outage capacity than that of the dipole antenna array.