Multipath Modelling for Terrestrial VHF Radio Direction Finding

摘要

This report details the development of computer models to investigate and explainthe effects of multipath on VHF radio direction finding (DF). The motivation for this development was to help explain the large and small scale multipath effects which occur for changes in transmitter and receiver position, or for changes in frequency. Particularly important in the analysis of current wide and narrow band DF approaches and the development of better ones. The new approach is based on representing the terrain and vegetation, which effect the signal path, by a large number of small (relative to the signal wavelength) isotropic reradiators. Polarization effects are not accounted for. Although this kind of approach can quickly become a computationally daunting task, a number of simplifications are introduced which greatly simplify the calculations. Two examples have been included illustrating the use of the proposed approach in the analysis and modelling real world measurements.