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// Example no 4.7
// To compute diffraction loss and identify Fresnel zone within which tip of obstruction lies for a)h=25m b)h=0 c)h=-25m
// Page no. 132
clc;
clear;
// Given data
lambda=1/3; // Wavelength in meter
d1=1*10^3; // Distance between transmitter and obstructing screen in m
d2=1*10^3; // Distance between receiver and obstructing screen in m
// a) For h=25m
h=25; // Effective heigth of obstruction screen in m
v=h*sqrt((2*(d1+d2))/(lambda*d1*d2)); // Fresnel diffraction parameter
printf('\n a) For h=25m Fresnel diffraction parameter v = %0.2f',v);
printf('\n From the plot of Knife-edge diffraction gain as a function of Fresnel diffraction parameter, diffraction loss is 22dB.');
Gd=-20*log10(0.225/v); // Diffraction loss for v>2.4 in dB
printf('\n Using numerical approximation, diffraction loss for v > 2.4 = %0.1f dB',Gd);
delta=(h^2/2)*((d1+d2)/(d1*d2)); // Path length difference between direct and diffracted rays
n=(2*delta)/lambda; // Number of Fresnel zones in which the obstruction lies
printf('\n Fresnel zone within which tip of obstruction lies = %0.2f',n);
printf('\n Therefore, the tip of obstruction completely blocks the first three Fresnel zones.');
// b) For h=0
h=0; // Effective heigth of obstruction screen in m
v=h*sqrt((2*(d1+d2))/(lambda*d1*d2)); // Fresnel diffraction parameter
printf('\n \n b) For h=0 Fresnel diffraction parameter v = %0.0f',v);
printf('\n From the plot of Knife-edge diffraction gain as a function of Fresnel diffraction parameter, diffraction loss is 6dB.');
Gd=-20*log10(0.5-0.62*v); // Diffraction loss for v=0 in dB
printf('\n Using numerical approximation, diffraction loss for v=0 = %0.0f dB',Gd);
delta=(h^2/2)*((d1+d2)/(d1*d2)); // Path length difference between direct and diffracted rays
n=(2*delta)/lambda; // Number of Fresnel zones in which the obstruction lies
printf('\n Fresnel zone within which tip of obstruction lies = %0.0f',n);
printf('\n Therefore, the tip of obstruction lies in middle of first Fresnel zone.');
// c) For h=-25m
h=-25; // Effective heigth of obstruction screen in m
v=h*sqrt((2*(d1+d2))/(lambda*d1*d2)); // Fresnel diffraction parameter
printf('\n \n c) For h=-25m Fresnel diffraction parameter v = %0.2f',v);
printf('\n From the plot of Knife-edge diffraction gain as a function of Fresnel diffraction parameter, diffraction loss is approximately 1dB.');
Gd=0; // Diffraction loss for v<-1 in dB
printf('\n Using numerical approximation, diffraction loss for v < -1 = %0.0f in dB',Gd);
delta=(h^2/2)*((d1+d2)/(d1*d2)); // Path length difference between direct and diffracted rays
n=(2*delta)/lambda; // Number of Fresnel zones in which the obstruction lies
printf('\n Fresnel zone within which tip of obstruction lies = %0.2f',n);
printf('\n Therefore, the tip of obstruction completely blocks the first three Fresnel zones but diffraction loss is negligible.');
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