Once you filter a signal, what is the best way to get the original signal back? Thanks..
opposite of a filter
Started by ●May 6, 2009
Reply by ●May 6, 20092009-05-06
"sauwen" <sauwen.jl@gmail.com>> Once you filter a signal, what is the best way to get the original signal > back?Use a time machine.> Thanks..You're welcome. -- Andrew
Reply by ●May 6, 20092009-05-06
>"sauwen" <sauwen.jl@gmail.com> > >> Once you filter a signal, what is the best way to get the originalsignal>> back? > >Use a time machine. > >> Thanks.. > >You're welcome. > >-- >Andrew > > >Ha ha.. If only one exists. Seriously, is there a way? I.e. with a simple filter? Thanks!
Reply by ●May 6, 20092009-05-06
>"sauwen" <sauwen.jl@gmail.com> > >> Once you filter a signal, what is the best way to get the originalsignal>> back? > >Use a time machine. > >> Thanks.. > >You're welcome. > >-- >Andrew > > >Ha ha.. If only one exists. Seriously, is there a way? I.e. with a simple filter? Thanks!
Reply by ●May 6, 20092009-05-06
sauwen wrote:>> "sauwen" <sauwen.jl@gmail.com> >> >>> Once you filter a signal, what is the best way to get the original > signal >>> back? >> Use a time machine. >> >>> Thanks.. >> You're welcome. >> >> -- >> Andrew >> >> >> > Ha ha.. If only one exists. > Seriously, is there a way? I.e. with a simple filter? > Thanks!There is no way to retrieve the original signal if the filter eliminates part of the signal. If the filter merely reshaped the frequency response without eliminating any part of it, a complementary filter can restore the original. See preemphasis. deemphasis. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●May 6, 20092009-05-06
On Wed, 06 May 2009 20:25:08 -0400, Jerry Avins wrote:> sauwen wrote: >>> "sauwen" <sauwen.jl@gmail.com> >>> >>>> Once you filter a signal, what is the best way to get the original >> signal >>>> back? >>> Use a time machine. >>> >>>> Thanks.. >>> You're welcome. >>> >>> -- >>> Andrew >>> >>> >>> >> Ha ha.. If only one exists. >> Seriously, is there a way? I.e. with a simple filter? Thanks! > > There is no way to retrieve the original signal if the filter eliminates > part of the signal. If the filter merely reshaped the frequency response > without eliminating any part of it, a complementary filter can restore > the original. See preemphasis. deemphasis. >I.e. if the filter has a zero at some frequency, that portion of the signal is irretrievably lost. Worse, what you get out of a real filter is filtered signal + a bit of noise, so where the filter attenuates the signal a great deal you've effectively lost the original information regardless of what a light reading of the theory may say. -- http://www.wescottdesign.com
Reply by ●May 6, 20092009-05-06
On May 7, 11:53�am, "sauwen" <sauwen...@gmail.com> wrote:> Once you filter a signal, what is the best way to get the original signal > back? > > Thanks..Deconvolution is the way - at least optimal in the sense of least squares. Hardy
Reply by ●May 7, 20092009-05-07
HardySpicer <gyansorova@gmail.com> wrote:> On May 7, 11:53?am, "sauwen" <sauwen...@gmail.com> wrote:>> Once you filter a signal, what is the best way to get >> the original signal back?> Deconvolution is the way - at least optimal in the sense > of least squares.Sometimes you can just invert the filter, but yes I believe that deconvolution is better in many cases. I recommend "Deconvolution of Images and Spectra" by Jansson, especially for non-linear deconvolution. -- glen
Reply by ●May 7, 20092009-05-07
glen herrmannsfeldt wrote:> HardySpicer <gyansorova@gmail.com> wrote: >> On May 7, 11:53?am, "sauwen" <sauwen...@gmail.com> wrote: > >>> Once you filter a signal, what is the best way to get >>> the original signal back? > >> Deconvolution is the way - at least optimal in the sense >> of least squares. > > Sometimes you can just invert the filter, but yes I believe > that deconvolution is better in many cases. I recommend > "Deconvolution of Images and Spectra" by Jansson, especially > for non-linear deconvolution. >What is the difference between deconvolution and inverse filtering ? I thought they were the same thing (at least for linear systems) ? Paul
Reply by ●May 7, 20092009-05-07
On 7 Mai, 10:39, Paul Russell <pruss...@sonic.net> wrote:> glen herrmannsfeldt wrote: > > HardySpicer <gyansor...@gmail.com> wrote: > >> On May 7, 11:53?am, "sauwen" <sauwen...@gmail.com> wrote: > > >>> Once you filter a signal, what is the best way to get > >>> the original signal back? > > >> Deconvolution is the way - at least optimal in the sense > >> of least squares. > > > Sometimes you can just invert the filter, but yes I believe > > that deconvolution is better in many cases. �I recommend > > "Deconvolution of Images and Spectra" by Jansson, especially > > for non-linear deconvolution. > > What is the difference between deconvolution and inverse filtering ? I > thought they were the same thing (at least for linear systems) ?For all intents and purposes, 'inverse filtering; is one of many ways to do deconvolution. If our filter is known to you has the right properties (all zeros and poles strictly inside the unit circle), the inverse filer will work, except for numerical artifacts. The ideal situation where everything works your way (filter is known, parameters favorable) doesn't occur very often. 'Deconvloution' covers all the other cases where you either have only crude information about the filter, and/or the inverse filter becomes unstable. Rune
