>westocl wrote: > > ... > >>> The coefficients aren't end-for-end symmetric so this isn't linear >>> phase. > > ... > >>> How do sidebands relate to this? I thought it was baseband. What >>> modulates the signal? >>> >>> You haven't explained why the function must be everywhere greater than>>> zero, or why that should be obvious. > > ... > >> We'll when i call my responses 'linear', i mean the group delay is >> approximately constant which indeed it is. They are not symmetric,thats>> why I feel that the responses are interesting. > >A little advice: when you make a startling claim, give words their >normal meanings. When you mean "almost", say so. > >>> How do sidebands relate to this? >> >> I just meant the function i tried to approximate had a max amplitude of1>> and the one created with the filter obviously creates a positive and >> negative frequency components whose amplitudes are each .5 > >I'm not clear what you're doing. The coefficients of your filter are all>real, so a real input will produce a real output. Moreover, filters >modify the frequency content of a signal, but you asked for a time >response and I gave you one. I'm not sure what you did with it or what >you expect the result to represent. How do negative frequencies enter >into this? > >>> You haven't explained why the function must be everywhere greater than>>> zero, or why that should be obvious. >> >> This is not so straight forward. but i shall try to explain....afterother>> things happen, Im kinda piecing back together a fourier series withthe>> added constraint that the phases must add up in a specific order. The >> algorithm treats every pice of the puzzle with equal importance., so ifi>> shall allow it to go after this zero amplitude case its error in >> approximating the origional function at that point vs the pointprevious>> to it will be infinite and it will want to quit and give me something >> bogus., There are ways of getting around that, but at this point immore>> interested in seening what it can do vs what makes it quit. >> >> If i could get zero, I could build a brick wall linearphase filter. >> Currently i can get 300 dB from a 200pt filter with corner .25Fs given200>> taps. > >You have numerical difficulties with zero that the standard workarounds >won't deal with. What's with negative numbers? > >> on another note, if we should allow it to run 2000 points... the phase >> cloning response will have been almost perfect. > >So why don't you? > >Jerry >-- >Engineering is the art of making what you want from things you can get. >???????????????????????????????????????????????????????????????????????I can, it just takes about an hour to run. (bummer).
Arbitrary Amplitude FIRs
Started by ●March 10, 2008
Reply by ●March 11, 20082008-03-11
Reply by ●March 11, 20082008-03-11
westocl wrote: ...>>> If i could get zero, I could build a brick wall linearphase filter. >>> Currently i can get 300 dB from a 200pt filter with corner .25Fs given > 200 >>> taps. >> You have numerical difficulties with zero that the standard workarounds >> won't deal with. What's with negative numbers? >> >>> on another note, if we should allow it to run 2000 points... the phase >>> cloning response will have been almost perfect.>> So why don't you?...> I can, it just takes about an hour to run. (bummer).You didn't answer: What's with negative numbers? (And why doesn't replacing zero with 1e-9 work for you as it does for most others?) Jerry -- Engineering is the art of making what you want from things you can get.
