Application of characteristic modes analysis in the design of multi-access antennas for an opportunistic radio system

A new design method for multi-access antennas is presented. This method is based upon characteristic modes analysis assuming the microstrip antennas as a resonant cavity, independently of its geometry. The principle is illustrated by the design of a multi-ports hexagonal patch antenna. After identifying the proper resonant modes of the structure, two access ports are positioned, and the spatial distribution of the two excited modes are accurately analysed for recovering perfect matching and isolation conditions at the same frequency band. A spatial diversity is consequently achieved, with potential applications such as MIMO or opportunistic radio systems.