# [Moved]: near field to far field transformation code error

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#### rashlots

##### Newbie level 1
clc

 Code PHP (brief) - [expand] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 lambda=0.1; %----------- scanning area definition ------------------------------------ velikostX = 20*lambda; % size of the scanning area velikostY = velikostX; Nx = (velikostX/lambda)*2+3; % samples at x axis x = linspace(-(velikostX/2), (velikostX/2), Nx); dx = abs(x(2)-x(1)); Ny = Nx; % samples at y axis y = linspace(-(velikostY/2), (velikostY/2), Ny); r0 = 2*lambda; % distance of scanning surface from the AUT     %------- testing antenna (AUT) definition (nine-dipole antenna) ---------- Nd = 9; % number of dipoles dd = lambda/2; % dipole spacing d = linspace((-(Nd-1)/2)*dd, ((Nd-1)/2)*dd, Nd); I = ones(1,Nd); % currents for dipoles (1 A) l = lambda/4; % dipole lenght Fd = j*(cos(k*l)*cos(theta)-cos(k*l))/(sin(theta)); % radiation function of symetric dipole     %----------- near-field samples computation ------------------------------- E = zeros(Nx,Ny); Ehelp = zeros(1,Nd); % help vector for m=1:Ny for n=1:Nx for i=1:Nd E(n,m) = E(n,m) + 60*(cos(k*l*(x(n)/sqrt(r0^2+(y(m)-d(i))^2+x(n)^2)))-cos(k*l))/(sqrt(r0^2+(y(m)-d(i))^2)/sqrt(r0^2+(y(m)-d(i))^2+x(n)^2))*I(i)*(exp(-j*k*sqrt(r0^2+(y(m)-d(i))^2+x(n)^2))/sqrt(r0^2+(y(m)-d(i))^2+x(n)^2)); end end end Emax = max(E); maxE = max(Emax); Eneardb = 20*log(abs(E/maxE)); figure(1); % 3D near-fiel distribution surf(x/lambda,y/lambda,Eneardb); title('Rozlozeni normovaneho modulu pole v blizke oblasti (z = 2*lambda)'); xlabel('y[lambda]'); ylabel('x[lambda]'); zlabel('abs(Enear)'); % depiction of E (module and phase) in the near-field for two orthogonal cuts figure(2); subplot(2,2,1); plot(x/lambda,Eneardb(:,((Ny+1)/2))); title('rez rovinou y = 0'); xlabel('x[lambda]'); ylabel('abs(Enear)'); subplot(2,2,2); plot(y/lambda,Eneardb(((Nx+1)/2),:)); title('rez rovinou x = 0'); xlabel('y[lambda]'); ylabel('abs(Enear)'); subplot(2,2,3); plot(x/lambda,angle(E(:,((Ny+1)/2)))/(2*pi)*360); xlabel('x[lambda]'); ylabel('phase(Enear)'); subplot(2,2,4); plot(y/lambda,angle(E(((Nx+1)/2),:))/(2*pi)*360); xlabel('y[lambda]'); ylabel('phase(Enear)');

%TILL HERE I WAS ABLE TO GENERATE PLOTS,
% nOW THE PROBLEM RISES TO SELECT THE VALUE OF t

 Code PHP (brief) - [expand] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 %----------- near-field to far-field transformation -------------------- A = zeros(t,t); % spatial spectrum computation for m=1:t for n=1:t for h=1:Ny for i=1:Nx A(n,m) = A(n,m) + E(i,h)*exp(j*k*(x(i)*kx(n,m)+y(h)*ky(n,m))); end end end t-m end A = A/(Nx*Ny);           % ------ far-field computation (theoretical values for comparison) ----------- Evzdal = zeros(t,t); for m=1:t for n=2:(t-1) Evzdal(m,n) = ((cos(k*l*cos(phi(n)))-cos(k*l)) / sin(phi(n)))*(sin(Nd/2*k*dd*cos(theta(m)+pi/2)))/(sin(1/2*k*dd*cos(theta(m)+pi/2))); end end Evzdalmax = max(Evzdal); maxEvzdal = max(Evzdalmax); Evzdal = abs(Evzdal/maxEvzdal); Evzdaldb = 20*log(Evzdal); figure(3); surf(phi/(2*pi)*360,theta/(2*pi)*360,Evzdaldb); title('Vyzarovaci diagram ziskany vypoctem'); xlabel('phi[°]'); ylabel('theta[°]'); zlabel('abs(Efar)'); % -------- multiplying the angular spectrum by a wavenumber ------------------ for i=1:t A(i,:) = kz.*A(i,:); A(:,i) = rot90(kz).*A(:,i); end           Amax = max(A); maxA = max(Amax); A = A/maxA; F = abs(A); Fdb = 20*log(F); figure(4); % depiction of spatial spectrum for two orthogonal cuts subplot(2,1,1); stem(ky(:,45),abs(A(:,45))); title('Rez prostorovym spektrem v rovine kx=0'); xlabel('ky'); ylabel('abs(A)'); subplot(2,1,2); stem(kx(45,:),abs(A(45,:))); title('Rez prostorovym spektrem v rovine ky=0'); xlabel('kx'); ylabel('abs(A)'); figure(6); % theoretical and transformed values comparison subplot(2,1,1); plot(theta(2:(t-1))/(2*pi)*360,Evzdaldb(2:(t-1),45),'b',theta(2:(t-1))/(2*pi)*360,Fdb(2:(t-1),45),'r'); xlabel('theta[°]'); ylabel('abs(Evzdal/Emax)'); subplot(2,1,2); plot(theta(2:(t-1))/(2*pi)*360,Evzdaldb(45,2:(t-1)),'b',theta(2:(t-1))/(2*pi)*360,Fdb(45,2:(t-1)),'r'); xlabel('phi[°]'); ylabel('abs(Evzdal/Emax)');

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