doc iffft

Documentation of the iffft function.

helpFun('iffft')

 Inverse Fast Finite Fourier Transform

 Y = IFFFT(X)

 Description
     Inverse Fourier transform of an input signal.

 Input parameters
     X [double(:inf x 1)] is the input signal.

 Output parameters
     Y [double(:inf x 1)] is the inverse Fourier-transformed signal

 Example
     % Sampling frequency
     Fs = 1000;            
     % Sampling period
     dt = 1/Fs;             
     % Length of signal
     L = 6000;             
     % Time vector
     t = (0:L-1)'*dt;
     % Signal
     S = 0.7*sin(2*pi*50*t) + sin(2*pi*120*t);
     xgtt = S + 2*randn(size(t));
     % Pad with zero so that the first value of xgtt is not lost in the
     % Fourier transformations
     xgtt=[0;xgtt];
     % Apply the fft function of OpenSeismoMatlab
     FASsignalOSM=ffft(xgtt)*dt;
     % Calculate inverse Fourier transform
     y=iffft(FASsignalOSM/dt);
     y=y(1:L-1);
     % Plot the initial ground motion and the inverse Fourier transform
     % of the Fourier-transformed motion
     plot(real(y))
     hold on
     plot(xgtt(2:L))
     hold off
     % Difference between results
     max(abs(real(y)-xgtt(2:L)))

__________________________________________________________________________
 Copyright (c) 2018-2022
     George Papazafeiropoulos
     Major, Infrastructure Engineer, Hellenic Air Force
     Civil Engineer, M.Sc., Ph.D.
     Email: gpapazafeiropoulos@yahoo.gr
 _________________________________________________________________________

Published with MATLAB® R2022b