perform interpolation using an ideal root raised cosine filter in the frequency domain in matlab

main.m
x = [1 2 3 4];     % Input signal
L = 4;             % Up-sampling factor
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main.m
N = length(x);        % Length of input signal
T = N + (N-1)*(L-1);  % Length of up-sampled signal
F = (0:T-1)/T;        % Frequency vector

% Define the transfer function of the RRC filter in the frequency domain
H_rrc = sqrt(L)*sinc(F/L).*sqrt(cos(pi*F/L).^2 + (2*L*F/sqrt(2*pi)).^2);
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main.m
X = fft(x, T);  % Fourier transform of input signal
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main.m
Y = X.*H_rrc;  % Filtered spectrum
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main.m
y = ifft(Y);  % Filtered signal
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