Circuit Modeling of Huygens Surfaces

Huygens surfaces are a recently proposed way of manipulating electromagnetic wavefronts using a superposition of subwavelength electric and magnetic dipoles situated on a plane. This allows for interesting phenomena such as refraction, beam manipulation, and focusing using this planar screen. In this letter, a circuit model for the unit cells comprising a Huygens surface is proposed to further understand the functionality of this screen. The equivalent circuit is a lattice network whose constituent series and shunt impedances correspond to the impedances of the magnetic and electric dipoles, respectively. We demonstrate that the corresponding voltage and current terminal relations across the lattice network correspond exactly to the electromagnetic boundary conditions across the Huygens surfaces. We also show how this model can be used to design the required unit cells and, using a two-dimensional circuit solver, how these lattice cells can be used to model an entire Huygens surface.