DFT and IDFT using Mathematical Formula

clc
clear all
close all

X=input('Enter the Input Sequence');
N=input('Enter the N value such that N-point DFT is calculated');
%Inputs are given%

L=length(X);

if N>L
    X=[X zeros(1,N-L)];
else
    X=X(1:N);
end
%Adjusting the Length of the input Sequence by appending Zeros or truncating the sequence%

for k=1:N
    key=0;
    for n=1:N
        key=key+X(n)*exp(-(j*2*pi*(k-1)*(n-1))/N);
    end
    Y(k)=key;
end
%DFT is calculated%

Y %DFT is printed%

L=length(Y);
n=0:1:L-1;

figure,plot(n,abs(Y)),title('Magnitude Response of DFT')
figure, plot(n, angle(Y)), title('Phase Response of DFT')
%MAGNITUDE and PHASERESPONSE OF DFT SIGNAL IS PLOTTED%

for k=1:N
    key=0;
    for n=1:N
        key=key+Y(n)*exp((j*2*pi*(k-1)*(n-1))/N);
    end
    Yinv(k)=key/N;
end
%IDFT is calculated%

Yinv

L=length(Y);
n=0:1:L-1;

figure,plot(n,abs(Yinv)),title('Magnitude Response of IDFT')
figure, plot(n, angle(Yinv)), title('Phase Response of IDFT')
%MAGNITUDE and PHASERESPONSE OF ORIGINAL SIGNAL IS PLOTTED%

%We are going to get a very minute phase due to the approximations of exponent values in the order of 10^-15%

Error using input
Cannot call INPUT from EVALC.

Error in dftidft2 (line 5)
X=input('Enter the Input Sequence');

Published with MATLAB® R2013b