Added frft functions towards codegen (c code on PS)

frft_codegen/fracF_cg.m

@@ -0,0 +1,80 @@
+function F = fracF_cg(f, a)
+%#codegen
+%% fracF_cg Fractional Fourier Transform (FrFT) - codegen-ready version
+%
+%   Author: Canisio Barth
+%
+%   F = fracF_cg(f, a) computes the Fractional Fourier Transform (FrFT)
+%   of the input signal 'f' for a single transform order 'a'.
+%
+%   This version is adapted for MATLAB Coder and hardware-oriented workflows.
+%
+%   Key characteristics:
+%       - Fixed input size: [1024 x 1] complex(single)
+%       - Output size: [512 x 1] complex(single)
+%       - Assumes input 'f' is already interpolated externally
+%       - No input validation (assumes valid scalar 'a' in core region)
+%       - Deterministic execution (no branching, no dynamic allocation)
+%
+%   INPUTS:
+%       f   - [1024 x 1] complex(single)
+%       a   - scalar single
+%
+%   OUTPUTS:
+%       F   - [512 x 1] complex(single)
+%
+%   Notes:
+%       - Internal FFT size = 2048
+%       - Designed for code generation and future FPGA mapping
+
+% Fixed sizes
+N    = 1024;
+%N2   = 512;
+Nfft = 2048;
+
+% Ensure types
+pi_s = single(pi);
+
+% Transform parameter
+phi = a * (pi_s / 2);
+
+% Precompute trig terms
+tan_half_phi = tan(phi / 2);
+sin_phi = sin(phi);
+cos_phi = cos(phi);
+
+csc_phi = 1 / sin_phi;
+cot_phi = cos_phi / sin_phi;
+
+twoDelta = 2 * sqrt(single(N) / 2);
+
+%% === Chirp A ===
+n = single((-N/2:N/2-1).') / twoDelta;
+
+Achirp = exp(-1j * pi_s * (n .* n) * tan_half_phi);
+
+%% Chirp multiplication #1
+g = Achirp .* f;
+
+%% === Chirp B ===
+m = single((-N:N-1).') / twoDelta;
+
+Bchirp = exp(1j * pi_s * csc_phi .* (m .* m));
+
+%% === Zero-padded buffer ===
+g_pad = complex(zeros(Nfft,1,'single'));
+g_pad(1:N) = g;
+
+%% === FFT convolution ===
+G = ifft( fft(g_pad) .* fft(Bchirp) );
+
+%% Extract valid part and decimate
+G_valid = G(N+1:2:end);   % [512 x 1]
+
+%% Complex phase constant
+Aphi = sqrt(1 - 1j * cot_phi);
+
+%% === Chirp multiplication #2 ===
+F = (Aphi / twoDelta) .* G_valid .* Achirp(1:2:end);
+
+end