Lets say I have a filter with a cutoff at 100Hz and my sampling rate is 1kHz. This means my cutoff is at 0.1 in normalized frequency terms. But it seems that the matlab freqz function plots my cutoff as being at 0.2, because it defines normalized as being relative to the nyquist. Is this not really confusing? If I'm referencing the freqz graph, I guess I'll need to say that the cutoff has a normalised frequency of 0.2 (with respect to the nyquist). Would that be clear?
Normalized frequency (freqz function)
Started by ●June 29, 2005
Reply by ●June 29, 20052005-06-29
aine_canby@yahoo.com wrote:> Lets say I have a filter with a cutoff at 100Hz and my sampling rate is > 1kHz. This means my cutoff is at 0.1 in normalized frequency terms. But > it seems that the matlab freqz function plots my cutoff as being at > 0.2, because it defines normalized as being relative to the nyquist. Is > this not really confusing?Well, obviously the folks at The Mathworks (tm) liked it. I would prefer something relative to sampling rate.> > If I'm referencing the freqz graph, I guess I'll need to say that the > cutoff has a normalised frequency of 0.2 (with respect to the nyquist). > Would that be clear? >As clear as you can get. You could also see if you can't plot a graph against actual frequency. -- ------------------------------------------- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●June 30, 20052005-06-30
You could alternatively enter the sampling frequency and view results in Hz b=[1 1 1 1]; a=1; freqz(b,a,256,1000); OR, if you really want normalized freqz(b,a,256,1); axs=(findobj(gcf,'type','axes')); for idx=1:2; xlabel(axs(idx),'Normalized Freq'); end another usefull tool is fvtool fvtool(b,a,256,1); now right hand click on xlabel and change to what you want <aine_canby@yahoo.com> wrote in message news:1120066800.034628.194360@g44g2000cwa.googlegroups.com...> Lets say I have a filter with a cutoff at 100Hz and my sampling rate is > 1kHz. This means my cutoff is at 0.1 in normalized frequency terms. But > it seems that the matlab freqz function plots my cutoff as being at > 0.2, because it defines normalized as being relative to the nyquist. Is > this not really confusing? > > If I'm referencing the freqz graph, I guess I'll need to say that the > cutoff has a normalised frequency of 0.2 (with respect to the nyquist). > Would that be clear? >