Termination-dependent diversity performance of coupled antennas: Network theory analysis

A new analysis of mutually coupled diversity antenna systems is presented that includes the effects of coupling on the radiation pattern and received power. This analysis, based upon the network scattering parameters, makes use of the singular value decomposition to both specify the characteristics of and analyze terminated antenna networks. The approach facilitates a simplified proof of the multiport conjugate matching condition as well as development of expressions for diversity performance as a function of various impedance terminations. Application of the analysis to coupled dipole antennas characterized using full-wave electromagnetic analysis leads to a comprehensive examination of the diversity performance obtainable for such antennas under different termination conditions. The results from this paper reveal that for closely spaced antennas, the termination can play a noticeable role in determining the diversity gain offered by coupled antennas.