Window Design of Digital Filters

Hi. I am calling the fir1 function to design an FIR filter. One argument of fir1 is the type of window that is to be used, e.g., hann, hamming, etc. However, the type of window depends on the stopband attentuation that one requires. So, I have an if ... else ... end conditional prior to callng fir1. it looks like

if deltadB_max <= 21

FixedWindow = 'rectwin';

else

FixedWindow = 'bartlett';

end

Now, when I invoke fir1, how can pass the variable FixedWindow into the arguments of fir1? Thank you.

Answer 1

[Star Strider]

Both the rectwin and bartlett functions have a single length argument. That simplifies this considerably.

if deltadB_max <= 21
    FixedWindow = @(L) rectwin(L); 
else
    FixedWindow = @(L) bartlett(L);  
end

L = 35;
b = fir1(34,0.48,FixedWindow(L));               % Test Design

freqz(b,1)

That ran without error and gave the appropriate result when I ran it (R2020a) with different values for ‘deltadB_max’.

For windows that require more parameters or different parameters, this would need to be changed appropriately. I leave that to you.

.

[Kamal Premaratne]

Fantastic. Works like a charm. Thank you so very much. I guess I now do appreciate the fact that all the window functions have one argument. I'll have to look into it when I am done with solving these problems. Thanks again.

[Star Strider]

As always, my pleasure!