cannot use element wise operator in frequency response?

Hi guys,

I am trying to get the requency response of the averaging FIR filter using the element wise operator, code below:

Fs=8e3; % sampling frequency
Fc=170; % cutoff frequency
alpha=1-2*pi*Fc/Fs;
nb=round(log2(1/(1-alpha))); % number of shift to the right correspending to multiplication by alpha
NbPoints=1000;
Ndec=Fs/2/1000;
Fstart=1;
i=1:Ndec*NbPoints;
freq=Fstart*10.^(i/NbPoints);
H_f=(1-alpha)*cos(pi.*freq/Fs)/sqrt(1+(alpha^2)-2*alpha*cos(2*pi.*freq/Fs));
semilogx(freq,20*log10(abs(H_f)))

the problem the H_f provides me only one output and not the vector result. how can I fix this.

[Bruno Luong]

Code incomplete (what is s):

Fs=8e3; % sampling frequency
Fc=170; % cutoff frequency
alpha=1-2*pi*Fc/Fs;
nb=round(log2(1/(1-alpha))); % number of shift to the right correspending to multiplication by alpha
NbPoints=1000;
Ndec=Fs/2/1000;
Fstart=1;
i=1:Ndec*NbPoints;
freq=Fstart*10.^(i/NbPoints);
H_f=(1-alpha)*cos(s)/sqrt(1+alpha^2-2*alpha*cos(2*pi*freq/Fs));

Unrecognized function or variable 's'.

semilogx(freq,20*log10(abs(H_f)))

[SimTec]

my bad. I just corrected it.. I still do not get the value of the H_f as a vector

[Bruno Luong]

The division "/" before sqrt is NOT elemetwise division "./".

Answer 1

[Abderrahim. B]

Fs=8e3; % sampling frequency
Fc=170; % cutoff frequency
alpha=1-2*pi*Fc/Fs;
nb=round(log2(1/(1-alpha))); % number of shift to the right correspending to multiplication by alpha
NbPoints=1000;
Ndec=Fs/2/1000;
Fstart=1;
i=1:Ndec*NbPoints;
freq=Fstart*10.^(i/NbPoints)

freq = 1×4000

1.0023 1.0046 1.0069 1.0093 1.0116 1.0139 1.0162 1.0186 1.0209 1.0233 1.0257 1.0280 1.0304 1.0328 1.0351 1.0375 1.0399 1.0423 1.0447 1.0471 1.0495 1.0520 1.0544 1.0568 1.0593 1.0617 1.0641 1.0666 1.0691 1.0715

H_f=(1-alpha)*cos(pi.*freq/Fs)./sqrt(1+(alpha^2)-2*alpha*cos(2*pi.*freq/Fs))

H_f = 1×4000

1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000 1.0000

semilogx(freq,20*log10(abs(H_f)))