A transform space filtered, wide frequency-range implementation of the parabolic equation method

Modelling of point-to-point radio propagation over terrain is of interest in the design of radio systems working over obstructed radio paths, or which may be subject to sub-refractive fading, or in estimating the visibility of radar targets close to terrain. Practical implementation of Fourier split-step PEM to provide accurate prediction of field-strength deep into the terrain diffraction region, over a wide frequency range, faces significant challenges. At high frequencies a large transform size is required, and at low frequencies the artificial upper boundary must be sufficiently high and the absorber layer sufficiently thick, to prevent spurious reflections from the upper boundary interfering with the weak terrain diffracted field. An adaptation to the PE method is described, and tested for the canonical problems of wedge and smooth-Earth diffraction over the frequency range of 10 MHz to 100 GHz, and compared with path measurements from 150 MHz to 1.5 GHz.