Energy propagation model for UHF radio positioning systems

Single and dual Yagi arrays are normally used in UHF radio positioning systems which operate over distances up to few hundreds of kilometres. The Yagi possesses several nulls around the antenna axis and applications of Yagi are found in the areas where unidirectional and linearly polarized radiation is required. The energy propagation from a single Yagi is represented by energy flow lines which give the direction of energy propagation at any point, phase center and velocities of propagation are modelled based on the concept of energy flow.