Measurements and modeling of wave propagation over irregular terrain for signals in the VHF band

This paper presents a ray method for determining wave propagation over hilly terrain. Terrain profiles between the transmitting and receiving antennas are obtained from digital maps, and a profile linearization method is developed to simplify those terrain profiles into 2-D wedges and trapezoids. A heuristic uniform theory of diffraction (UTD) solution including multiple-edge transition zone diffractions is then applied to determine path losses for waves propagating through those 2-D structures. All forward diffracting contributions, plus a ground reflection near the receiving antenna, are included to evaluate the field distributions. Measurements of VHF TV signals in northern Taiwan have been performed to compare with the UTD simulations. Good agreements are obtained, considering the complexity of wave propagation through irregular terrain.