I face problem to design and write the SRRC filter in frequency domain and then after take IFFT in time domain according to the equation 28 in [C filter design], the attachment is consist on the equation
.also i already was wrote the code but i dont get the desired result My code is
M=5;
K=128;
a=0.75;
N=K*M;
T=1;
fL=(1-a)/2*T;
fH=(1+a)/2*T;
f = linspace(-fH,fH,N);
G=sqrt(0.5*T*(1+cos(((pi*T)./a)*(abs(f)-fL))));
G(find(abs(f)=fH))=0;
g =fftshift(G);
g=ifft(g,'symmetric')';
plot(f,g,'linewidth',2,'color','r')
grid on
Any help would be greatly appreciated!
Have a look on similar works, e.g., https://gssc.esa.int/navipedia/index.php/Square-Root_Raised_Cosine_Signals_(SRRC)
https://wirelesspi.com/design-nyquist-square-root-nyquist-pulse-shaping-filters/
https://www.gaussianwaves.com/2018/10/square-root-raised-cosine-pulse-shaping/
I spotted a couple of mistakes and misunderstandings of yours.
1) You missed brackets when defining fL & fH.
2) The order of ifft & ifftshift seems to be wrong.
3) After inverse Fourier transform your result is still complex valued --> you need to plot the real part.
Not sure whether result makes sense, have a look:
Code:
M=5;
K=128;
a=0.75;
N=K*M;
T=1;
% brackets!
fL=(1-a)/(2*T);
fH=(1+a)/(2*T);
f = linspace(-fH,fH,N);
G = sqrt(0.5*T*(1+cos(((pi*T)./a)*(abs(f)-fL))));
G(find(abs(f)=fH))=0;
% Change order of ifft & ifftshift
g = ifft(G);
g = ifftshift(g);
figure
plot(f,real(g),'linewidth',2,'color','r') % take real part
grid on
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