Semi-Infinite Array

This is a problem in which a structure repeats periodically to infinity. It is closely related to the Infinite Array problem but is much more challenging due to the fact that the solution cannot be assumed periodic. The standard method is to solve for the Infinite Array and to subtract this solution from the solution for the semi-infinite array. Additional diffculties arise if the structure supports Rayleigh-Bloch Waves because this needs particular attention.