Abstract: Traditional central differential discrete mixed Fourier transform (DMFT) algorithms suffer from numerical oscillation when computing the mixed dynamic impedance boundary conditions, and from increased errors for neglecting backward-propagation and diffraction waves. A recursive two-way DMFT (TW-DMFT) algorithm is proposed in this paper using a mixed forward-backward difference method which is based on the traditional algorithm. The first order forward-backward difference equation is used to substitute for traditional central difference equation to fit the impedance boundary condition,and the recursively two-way parabolic equation model is used to improve the traditional one-way models. Compared with the traditional algorithm and geometrical theory of diffraction (GTD), the stability and accuracy which make up the deficiency and applicability of the traditional algorithm are improved by the TW-DMFT algorithm, which are verified by the simulation results that calculated in complex environments including single knife-edges and real terrain for different boundaries and media.

Key words: radio propagation, propagation algorithm, discrete mixed Fourier transform algorithm, geometrical theory of diffraction, irregular terrain, difference equations