Characteristic Mode Analysis: Putting Physics back into Simulation

Characteristic-mode analysis (CMA) enables a systematic approach to antenna design and antenna placement. The approach is based on insight in the fundamental resonance characteristics of antenna geometries and of the structures on which they are mounted. This insight aids in choosing the locations of excitations on an antenna and of the antennas on a platform. Furthermore, knowledge of the coupling between excitations and modes enables a design engineer to synthesize the desired antenna pattern by exciting a linear combination of modal patterns. This is a deterministic approach, which is based on insight in physics. It contrasts with an approach in which an optimization routine is used to explore a large many-dimensional design space with few constraints. This paper offers a refresher on the theory of characteristic modes and presents practical examples that all use CMA in the design process and in the interpretation of results.