Theoretical analysis of nonreciprocal electromagnetic surface wave devices

An investigation of the possibility of building a low applied magnetic field isolator or nonreciprocal phase shifter at 90 GHz or at higher frequencies is given. The structure consists of a ferrite slab backed by a metal plate. A magnetic field is applied in the plane of the ferrite slab. By solving Maxwell's equations, including the equation of motion of magnetization, we show that under appropriate conditions surface waves on the structure can exist. We further show that for different ferrite slab thicknesses and different applied magnetic fields, only waves traveling along the slab traverse to the applied magnetic field can exist.