WP 1, D2 – Functional System Parameters description

BROADWAY, IST-2001-32686 WP1-D2 version 1, date 10-10-02 Programme: ISTwhere k0= 2πλ0denotes the wave number and λ0the wavelength of the wave.1∆z2θiθiθiθiAB2'1'Due to the fact that the height irregularity ( x y)Fig. 2.2-1: Geometry for roughness criterion.z , of the surface is a stochastic function of the horizontaldimensions x and y only the square root of the mean square of the phase differences ∆ ϕ can bedetermined.The operator ( )( )∆ ϕ2 = 2 k 0σ cosθ i.2⋅ denotes the average of the enclosed quantity and σ = ∆z is the surface roughness. Forsmall surface roughness σ the phase deviation between reflected or scattered ray becomes small. Hence thecomplex field strengths in the far field of the two rays are nearly in phase. The resultant far field nearlycoincides with the one from a perfectly smooth plane surface.2.2.1.1. Rayleigh CriterionAccording to Rayleigh, the average phase errorHence2∆ ϕ must remain smaller the 222 0( θ )πR i∆ϕ = k σ cos