Dyadic Green's function for an electric current source in the unit cell of a periodic structure

A dyadic Green's function for rectangular waveguides has been derived and discussed in [1–5]. None of these works, however, discusses the Green's function for a unit cell of a periodic structure. In this work the dyadic Green's function for an electric current source in a Floquet phase-shift-wall waveguide (unit cell) is derived using the magnetic vector potential. Complete solutions for the electric and magnetic fields in the unit cell, including the source region, are obtained in the form of known waveguide modes with periodic boundary conditions. To validate the theory the scattered field from an array of z-directed strips is computed using the new Green's function and compared with results obtained by the HFSS code. This dyadic Green's function can be used to analyze various periodic structures such as large array antennas and metamaterials.