Unwrapped phase from a fourier transform loses information. The method works fine in other packages.

using the following code, I should generate an unwrapped phase plot which should be a straight line. This has been checked in Igor and does as expected. In matlab, the first few thousand data points and the final few thousand produce a straight line as expected, however in the middle, the information is apparently lost.

x=0:1:49999;

A=single(exp(-(x-1000).^2/10^2)-exp(-(x-1010).^2/10^2));

B=fft(A);

C=real(B);

D=imag(B);

E=atan(D./C); %this can also be done with E=(cart2pol(D,C))

F=unwrap(E);

plot(F)