Optimization of diversity antenna directivities based on spherical mode expansion

This paper proposes a new approach for designing diversity antenna directivities based on spherical mode expansion. The antenna directivity is expanded by spherical wave functions and spherical mode coefficients. Spherical mode coefficients, which specify the antenna directivity, can be estimated from a given antenna volume and an angular profile of incident waves. In this paper, we derive the optimal antenna directivities for diversity system in order to minimize outage probability of combined channel gain in the given environment. The optimal antenna matched to a given propagation environment can be designed by using this approach.