the plate. Perfect Electric Conducting (PEC) bodies can be recast This touches one of the problems of Physical Optics into a one-dimensional integral but involving relatively (PO) for large objects or close transmitters or receivers: easy to compute Fresnel integrals. This method has been the plane-wave approximation is not valid any more, applied to the computation of both ideal theoretical leading to fields that continue to grow if the size of the cases like a smooth sloping wedge at 100 MHz and scatterer is increased. Therefore, other solutions have to 1 GHz (for both co- and crosspolar fields), as well as to be found. Paper [LCDC02] is using a parabolic phase IE-copolar IE-copolar IE-crosspolar IE-crosspolar Measurement-copolar Measurement-copolar 2D-IE 2D-IE 10000 12000 10000 12000 Range in metres Range in metres (a) 144 MHz. (b) 435 MHz. Figure 4.7-2 Co- and crosspolar fields for Danish terrain. CHAPTER 4.7 Propagation modelling and channel characterisation Horizontal postion of scanner (m) Horizontal postion of scanner (m) (a) Measured results. (b) Simulated results. Figure 4.7-3 Amplitude of the reflected field of a 0.35 X 0.5 X 0.02 m Plexiglass plate at 5.8 GHz. approximation for this purpose, which has been de- simulations and measurements in an anechoic room on veloped in a previous COST Action, namely COST a flat plate also agree very well, both in amplitude, Action 259 -Wireless Flexible Personal Communications Figure 4.7-3, and in phase, Figure 4.7-4. (COST 259). This paper investigates many further re- finements of this Fresnel method such as Modal expansion models 1. the use of near-field formulas; Since this method is specially suited for closed areas, 2. using internal reflections in a reflecting plate of finite one contribution [Kyri03] has applied this method for thickness and material properties (permittivity and the evaluation of the K-factor of a hallway. Indeed, the permeability); Ray-Tracing (RT) methods are less appropriate to this kind of problem, since the number of reflections on the