Code covered by the BSD License

# MatLab Solutions: "Introduction to Digital Signal Processing: A Computer Laboratory Textbook".

### Ilias Konsoulas (view profile)

29 Oct 2012 (Updated )

These files are the MatLab solutions of exercises contained in the above DSP lab textbook.

```function X = splitradixfft(x)
% Split-Radix, Decimation-In-Time (DIT),FFT Computation function.
% Attention: Length of input signal x should be divisable by 4 and >=4.
% Attention: Only the first iteration of the algorithm is implemented here.

% Make sure x is row vector for subsequent processing:
x = x(:).';
N = length(x);
X = zeros(1,N);

% Generate sequences e[n], f[n], g[n] and h[n].
g = zeros(1,N/2);
h = zeros(1,N/4);
i  = zeros(1,N/4);

ind1 = 1:2:N-1;
ind2 = 2:4:N-2;
ind3 = 4:4:N;

g = x(ind1); % N/2 length signal made of samples: x[0], x[2], x[4],   ..., x[N-2].
h = x(ind2);  % N/4 length signal made of samples: x[1], x[5], x[9],   ..., x[N-3].
i = x(ind3);   % N/4 length signal made of samples: x[3], x[7], x[11], ..., x[N-1].

% Compute their N/2- and N/4-point DFT's:
% G = my_DFT(g);
% H = my_DFT(h);
% I = my_DFT(i);
G = fft(g);
H = fft(h);
I = fft(i);

% Create the phasor vector:
k = 0:N/4-1;
W = exp(-1i*2*pi*k/N);

% Apply the formulas.
X(1:N/4)             = G(1:N/4)         + W.*H     +      (W.^3).*I;
X(N/4+1:N/2)     = G(N/4+1:N/2) - 1i*W.*H + 1i*(W.^3).*I;
X(N/2+1:3*N/4) = G(1:N/4)          - W.*H      -      (W.^3).*I;
X(3*N/4+1:N)    = G(N/4+1:N/2) + 1i*W.*H -  1i*(W.^3).*I;```