Hybrid thin-slot algorithm for the analysis of narrow apertures in finite-difference time-domain calculations

A technique to incorporate a half-space aperture integral equation into a finite-difference time-domain (FDTD) code based on the offset Yee mesh (see K.S. Yee, ibid., vol. AP-14, p.302-7, 1966) is presented. To introduce the technique, linear apertures that are electrically narrow in both width and depth are discussed. The method incorporates an independent time-marching solution for the aperture problem into the FDTD code so that the aperture formally does not exist within the main FDTD mesh. A feedback scheme is introduced so that full exterior and interior coupling is included in the aperture solution. The technique is particularly useful for the analysis of apertures that are narrow both in width and depth with regard to the FDTD spatial cell. Previous thin-slot methods are shown to significantly underestimate the transverse gap electric field for this case, and an explanation for this is provided with the aid of the hybrid algorithm