INVESTIGATION OF THE PADE APPROXIMANT-BASED WIDE-ANGLE BEAM-PROPAGATION METHOD FOR ACCURATE MODELING OF WAVE-GUIDING CIRCUITS

An analytical and numerical study of the accuracy of the beam propagat ion method that includes approximate treatments of wide-angle propagat ion based on Pade rational functions is presented. The investigation i dentifies the error terms associated with a sequence of higher order o perators and the range of validity of different approximant operators is studied through examination of two-dimensional (2-D) waveguide stru ctures. An analytical model for the general error in Pade-based wide-a ngle schemes is developed and compared with numerical simulations of s imple waveguiding devices for which the exact solution is known. Guide lines for determining the range of error pertinent to the Pade operato r are established.