New interpretation of wave propagation in high impedance surfaces

A general framework based on a 4-port, 2-layer circuit model has been developed to describe surface wave propagation in periodic surfaces. For the specific case of high impedance surfaces, a new mechanism for the occurrence of electromagnetic band gaps is presented based on eigenmode analysis. It is shown that the eigenmode of a surface electromagnetic wave at any given frequency can be written as a linear combination of two "pure" modes: a backward wave mode that propagates primarily within the surface, and a forward wave mode that resides primarily on the surface. At the band gap frequencies, the two pure modes couple so as to result in no propagation. It is anticipated that the circuit model developed as part of this work will be a powerful tool fore understanding and exploration of a large class of periodic systems.