Is there a "DIGITAL" equivalent of "Q"?
in [DSP]
|
Prev: Rotate 2D Gaussian
Next: signal fades in noise
From: Richard Owlett on 26 Apr 2010 15:55 Please note quotation marks in subject ;) Also, I'm not the oldest on group --- BUT my father operated a *LEGAL* land based spark gap xmtr All that to say that I think in "linear passive discrete" domain rather than in "digital" domain. I have a "filter" problem. I have a reasonable idea on how to implement it. *UNFORTUNATELY* requires HENRY's and FARADs ;/ I can write and solve the associated mesh equations My solution will obviously be a subset of SPICE BUT will I be able to describe either PROBLEM or SOLUTION to those educated in digital domain? {for perspective -searching this group will reveal that I once threatened to implement FFT in COBOL ;\ } 0
From: Mark on 26 Apr 2010 18:32 On Apr 26, 3:55 pm, Richard Owlett <rowl...(a)pcnetinc.com> wrote: > Please note quotation marks in subject ;) > Also, I'm not the oldest on group --- BUT > my father operated a *LEGAL* land based spark gap xmtr > > All that to say that I think in "linear passive discrete" domain > rather than in "digital" domain. > > I have a "filter" problem. > I have a reasonable idea on how to implement it. > *UNFORTUNATELY* requires HENRY's and FARADs ;/ > I can write and solve the associated mesh equations > My solution will obviously be a subset of SPICE > > BUT will I be able to describe either > PROBLEM or SOLUTION > to those educated in digital domain? > > {for perspective -searching this group will reveal that I once > threatened to implement FFT in COBOL ;\ } > > 0 if you provide a frequency response and phase response (if you care) or a time domain response to the DSP person, they will be able to design your filter.. or you can try it yourself http://www.mds.com/download/filterdesign.asp with a free demo version (very) basically, selectivity relates to the number of taps.. higher selectivity = more taps... Mark
From: Tim Wescott on 26 Apr 2010 19:36 Richard Owlett wrote: > Please note quotation marks in subject ;) > Also, I'm not the oldest on group --- BUT > my father operated a *LEGAL* land based spark gap xmtr > > All that to say that I think in "linear passive discrete" domain rather > than in "digital" domain. > > I have a "filter" problem. > I have a reasonable idea on how to implement it. > *UNFORTUNATELY* requires HENRY's and FARADs ;/ > I can write and solve the associated mesh equations > My solution will obviously be a subset of SPICE > > BUT will I be able to describe either > PROBLEM or SOLUTION > to those educated in digital domain? > > {for perspective -searching this group will reveal that I once > threatened to implement FFT in COBOL ;\ } Q is a very nice number for 2nd-order time-invariant linear resonant systems (such as you might make with caps and coils). It's nice because it expresses a ratio that holds over a very wide range, and it has the same meaning for a system with a resonant frequency at 1Hz as a system with a resonant frequency at 1GHz. It's also more or less easily extensible to 3rd, 4th, and even infinite-order (i.e. transmission line) systems. It doesn't work so well with sampled time systems. There is sort of a concept of Q buried in there, but the closer you get to the sampling rate, the more "kinda" it gets. It is _not_ a nice convenient invariant ratio for a resonant frequency that changes with respect to the sampling rate. Alas. -- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
From: Richard Owlett on 26 Apr 2010 20:12 Mark wrote: Mark wrote: > On Apr 26, 3:55 pm, Richard Owlett <rowl...(a)pcnetinc.com> wrote: >> Please note quotation marks in subject ;) >> Also, I'm not the oldest on group --- BUT >> my father operated a *LEGAL* land based spark gap xmtr >> >> All that to say that I think in "linear passive discrete" domain >> rather than in "digital" domain. >> >> I have a "filter" problem. >> I have a reasonable idea on how to implement it. >> *UNFORTUNATELY* requires HENRY's and FARADs ;/ >> I can write and solve the associated mesh equations >> My solution will obviously be a subset of SPICE >> >> BUT will I be able to describe either >> PROBLEM or SOLUTION >> to those educated in digital domain? >> >> {for perspective -searching this group will reveal that I once >> threatened to implement FFT in COBOL ;\ } >> >> 0 > > if you provide a frequency response and phase response (if you care) > or a time domain response to the DSP person, they will be able to > design your filter.. > > or you can try it yourself > > http://www.mds.com/download/filterdesign.asp > > with a free demo version > > (very) basically, selectivity relates to the number of taps.. higher > selectivity = more taps... > > > Mark > > On Apr 26, 3:55 pm, Richard Owlett <rowl...(a)pcnetinc.com> wrote: >> Please note quotation marks in subject ;) >> Also, I'm not the oldest on group --- BUT >> my father operated a *LEGAL* land based spark gap xmtr >> >> All that to say that I think in "linear passive discrete" domain >> rather than in "digital" domain. >> >> I have a "filter" problem. >> I have a reasonable idea on how to implement it. >> *UNFORTUNATELY* requires HENRY's and FARADs ;/ >> I can write and solve the associated mesh equations >> My solution will obviously be a subset of SPICE >> >> BUT will I be able to describe either >> PROBLEM or SOLUTION >> to those educated in digital domain? >> >> {for perspective -searching this group will reveal that I once >> threatened to implement FFT in COBOL ;\ } >> >> 0 > > if you provide a frequency response and phase response (if you care) > or a time domain response to the DSP person, they will be able to > design your filter.. > > or you can try it yourself > > http://www.mds.com/download/filterdesign.asp > > with a free demo version > > (very) basically, selectivity relates to the number of taps.. higher > selectivity = more taps... > > > Mark > Thank you for your courteous reply. BUT I am a "curmudgeon" I ask for *EXPLICIT* definition of "Q" in *DIGITAL* domain.
From: cassiope on 27 Apr 2010 11:01
On Apr 26, 5:12 pm, Richard Owlett <rowl...(a)pcnetinc.com> wrote: > Mark wrote: > Mark wrote: > > On Apr 26, 3:55 pm, Richard Owlett <rowl...(a)pcnetinc.com> wrote: > >> Please note quotation marks in subject ;) > >> Also, I'm not the oldest on group --- BUT > >> my father operated a *LEGAL* land based spark gap xmtr > > >> All that to say that I think in "linear passive discrete" domain > >> rather than in "digital" domain. > > >> I have a "filter" problem. > >> I have a reasonable idea on how to implement it. > >> *UNFORTUNATELY* requires HENRY's and FARADs ;/ > >> I can write and solve the associated mesh equations > >> My solution will obviously be a subset of SPICE > > >> BUT will I be able to describe either > >> PROBLEM or SOLUTION > >> to those educated in digital domain? > > >> {for perspective -searching this group will reveal that I once > >> threatened to implement FFT in COBOL ;\ } > > >> 0 > > > if you provide a frequency response and phase response (if you care) > > or a time domain response to the DSP person, they will be able to > > design your filter.. > > > or you can try it yourself > > >http://www.mds.com/download/filterdesign.asp > > > with a free demo version > > > (very) basically, selectivity relates to the number of taps.. higher > > selectivity = more taps... > > > Mark > > > On Apr 26, 3:55 pm, Richard Owlett <rowl...(a)pcnetinc.com> wrote: > >> Please note quotation marks in subject ;) > >> Also, I'm not the oldest on group --- BUT > >> my father operated a *LEGAL* land based spark gap xmtr > > >> All that to say that I think in "linear passive discrete" domain > >> rather than in "digital" domain. > > >> I have a "filter" problem. > >> I have a reasonable idea on how to implement it. > >> *UNFORTUNATELY* requires HENRY's and FARADs ;/ > >> I can write and solve the associated mesh equations > >> My solution will obviously be a subset of SPICE > > >> BUT will I be able to describe either > >> PROBLEM or SOLUTION > >> to those educated in digital domain? > > >> {for perspective -searching this group will reveal that I once > >> threatened to implement FFT in COBOL ;\ } > > >> 0 > > > if you provide a frequency response and phase response (if you care) > > or a time domain response to the DSP person, they will be able to > > design your filter.. > > > or you can try it yourself > > >http://www.mds.com/download/filterdesign.asp > > > with a free demo version > > > (very) basically, selectivity relates to the number of taps.. higher > > selectivity = more taps... > > > Mark > > Thank you for your courteous reply. > BUT I am a "curmudgeon" > I ask for *EXPLICIT* definition of "Q" in *DIGITAL* domain. Perhaps it would be useful if you would tell us how you define Q in the analog domain (there's more than one way). |