[1] Viaducts over roads are common in many cities. In this paper, a three-dimensional multiray tracing model for in-vehicle mobile digital TV was used to explore the propagation properties of ultrahigh frequency waves under viaducts, subject to the transmitting antenna being higher than viaduct deck. The model is based on geometrical optics, physical optics, geometrical theories of diffraction, and especially the uniform theory of diffraction. The model takes into account direct propagation, ground reflection, transmission, as well as wedge diffraction to reveal the law of signal path gain under viaducts. Validation results show good agreement between calculated and measured data. The prediction for linearly, especially vertically polarized wave propagation provided by a six-ray model may be more helpful than that provided by a four-ray model.
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