Application of backward difference algorithm in radiowave prediction above earth surface

Using split-step fourier transform method solving parabolic equation is an effective method for predicting radiowave propagation above earth surface. In this paper the backward difference is adopted to improve the discrete mixed fourier transform algorithm, shift map method is also introduced to consider irregular terrains. Radiowave propagation is then predicted under vacuum and non-vacuum air conditions. Calculated results show clearly the effect of non-vacuum air condition to the radiowave propagation above earth surface.