Abstract
Of great interest in the many fields of communication is the requirement to place numerous small antenna elements in close proximity or even inside one another for diversity or mutiband usage. This letter aims to describe the effects of such adjacency in terms of physical distance and operating frequencies as a function of the volume overlap of circumscribing Wheeler-Chu spheres. We investigate any potential bandwidth advantage or in shared near-field space and define tradeoffs between space minimization and acceptable degradation for electrically small antennas. We find that contrary to popular belief among many antenna designers, it is not possible for two antennas having similar modes to reuse volume without suffering degradation in performance, particularly bandwidth.