> > >>>>> If the noise includes some DC it seems that a matched filter would
> > >>>>> treat it as a zero frequency "curve" and eliminate it in the
> > >>>>> convolution along with all the higher frequency noise.
> > >>>> What noise?
> > >>> The noise that got into the original signal has some AC and a DC
> > >>> offset.
> > >>> Matched filtering should eliminate the DC as well as the AC.
> > >>> Bret Cahill
> > >> How can a matched filter eliminate in-band noise? � DC or AC?
>
> > > That's someone else's issue.
>
> > The point is the assumption is flawed.
>
> > > The immediate issue here is if can you assume DC to be a zero
> > > frequency AC as far as matched filtering is concerned.
>
> > You can always assume it. �It may completely screw up your system
> > depending on its sensitivity to DC, though.
>
> > > If convolution in the time domain amounts to multiplication in the
> > > frequency domain then, at first glance, DC or square wave noise should
> > > be filtered along with the AC noise..
>
> > Convolution in TD is, in fact, multiplication in FD. � That doesn't
> > change the issue of eliminating noise or interference in the passband of
> > a filter.
>
> > It sounds to me like you are ascribing properties to matched filters
> > that they don't have, e.g., eliminating noise or DC from the passband.
>
> A simple analog R-to-ground C filter can eliminate DC so maybe that's
> not so much an issue.
>
> A bigger problem would be optimum pulse shaping when the 1st
> derivative of the signal needs to be, for other reasons, at a minimum
> as much as possible. �This consideration may outweigh the noise
> problems and I may be stuck with a simple sine wave.
>
> Is a simple sine wave any good in a matched filter or does the pulse
> shape need more "personality" something for FFT to munch on?
Mozart didn't like the flute for the same reason -- nothing but a
sterile sine wave.
Bret Cahill
Reply by Bret Cahill●September 21, 20092009-09-21
> >>>>> If the noise includes some DC it seems that a matched filter would
> >>>>> treat it as a zero frequency "curve" and eliminate it in the
> >>>>> convolution along with all the higher frequency noise.
> >>>> What noise?
> >>> The noise that got into the original signal has some AC and a DC
> >>> offset.
> >>> Matched filtering should eliminate the DC as well as the AC.
> >>> Bret Cahill
> >> How can a matched filter eliminate in-band noise? � DC or AC?
>
> > That's someone else's issue.
>
> The point is the assumption is flawed.
>
> > The immediate issue here is if can you assume DC to be a zero
> > frequency AC as far as matched filtering is concerned.
>
> You can always assume it. �It may completely screw up your system
> depending on its sensitivity to DC, though.
>
> > If convolution in the time domain amounts to multiplication in the
> > frequency domain then, at first glance, DC or square wave noise should
> > be filtered along with the AC noise..
>
> Convolution in TD is, in fact, multiplication in FD. � That doesn't
> change the issue of eliminating noise or interference in the passband of
> a filter.
>
> It sounds to me like you are ascribing properties to matched filters
> that they don't have, e.g., eliminating noise or DC from the passband.
A simple analog R-to-ground C filter can eliminate DC so maybe that's
not so much an issue.
A bigger problem would be optimum pulse shaping when the 1st
derivative of the signal needs to be, for other reasons, at a minimum
as much as possible. This consideration may outweigh the noise
problems and I may be stuck with a simple sine wave.
Is a simple sine wave any good in a matched filter or does the pulse
shape need more "personality" something for FFT to munch on?
Bret Cahill
Reply by Eric Jacobsen●September 21, 20092009-09-21
On 9/20/2009 6:37 PM, Bret Cahill wrote:
>>>>> If the noise includes some DC it seems that a matched filter would
>>>>> treat it as a zero frequency "curve" and eliminate it in the
>>>>> convolution along with all the higher frequency noise.
>>>> What noise?
>>> The noise that got into the original signal has some AC and a DC
>>> offset.
>>> Matched filtering should eliminate the DC as well as the AC.
>>> Bret Cahill
>> How can a matched filter eliminate in-band noise? DC or AC?
>
> That's someone else's issue.
The point is the assumption is flawed.
> The immediate issue here is if can you assume DC to be a zero
> frequency AC as far as matched filtering is concerned.
You can always assume it. It may completely screw up your system
depending on its sensitivity to DC, though.
> If convolution in the time domain amounts to multiplication in the
> frequency domain then, at first glance, DC or square wave noise should
> be filtered along with the AC noise..
Convolution in TD is, in fact, multiplication in FD. That doesn't
change the issue of eliminating noise or interference in the passband of
a filter.
It sounds to me like you are ascribing properties to matched filters
that they don't have, e.g., eliminating noise or DC from the passband.
--
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com
Reply by Eric Jacobsen●September 21, 20092009-09-21
On 9/20/2009 10:37 AM, Jerry Avins wrote:
> Eric Jacobsen wrote:
>> On 9/19/2009 12:59 PM, Bret Cahill wrote:
>>>>> If the noise includes some DC it seems that a matched filter would
>>>>> treat it as a zero frequency "curve" and eliminate it in the
>>>>> convolution along with all the higher frequency noise.
>>>> What noise?
>>>
>>> The noise that got into the original signal has some AC and a DC
>>> offset.
>>>
>>> Matched filtering should eliminate the DC as well as the AC.
>>>
>>>
>>> Bret Cahill
>>
>> How can a matched filter eliminate in-band noise? DC or AC?
>
> It depends on who determines what is a "match". Consider the nopass filter.
>
> Jerry
Good point. ;)
--
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com
Reply by Bret Cahill●September 20, 20092009-09-20
> >>> If the noise includes some DC it seems that a matched filter would
> >>> treat it as a zero frequency "curve" and eliminate it in the
> >>> convolution along with all the higher frequency noise.
> >> What noise?
>
> > The noise that got into the original signal has some AC and a DC
> > offset.
>
> > Matched filtering should eliminate the DC as well as the AC.
>
> > Bret Cahill
>
> How can a matched filter eliminate in-band noise? � DC or AC?
That's someone else's issue.
The immediate issue here is if can you assume DC to be a zero
frequency AC as far as matched filtering is concerned.
If convolution in the time domain amounts to multiplication in the
frequency domain then, at first glance, DC or square wave noise should
be filtered along with the AC noise..
Bret Cahill
Reply by Jerry Avins●September 20, 20092009-09-20
Eric Jacobsen wrote:
> On 9/19/2009 12:59 PM, Bret Cahill wrote:
>>>> If the noise includes some DC it seems that a matched filter would
>>>> treat it as a zero frequency "curve" and eliminate it in the
>>>> convolution along with all the higher frequency noise.
>>> What noise?
>>
>> The noise that got into the original signal has some AC and a DC
>> offset.
>>
>> Matched filtering should eliminate the DC as well as the AC.
>>
>>
>> Bret Cahill
>
> How can a matched filter eliminate in-band noise? DC or AC?
It depends on who determines what is a "match". Consider the nopass filter.
Jerry
--
Engineering is the art of making what you want from things you can get.
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Reply by Eric Jacobsen●September 20, 20092009-09-20
On 9/19/2009 12:59 PM, Bret Cahill wrote:
>>> If the noise includes some DC it seems that a matched filter would
>>> treat it as a zero frequency "curve" and eliminate it in the
>>> convolution along with all the higher frequency noise.
>> What noise?
>
> The noise that got into the original signal has some AC and a DC
> offset.
>
> Matched filtering should eliminate the DC as well as the AC.
>
>
> Bret Cahill
How can a matched filter eliminate in-band noise? DC or AC?
--
Eric Jacobsen
Minister of Algorithms
Abineau Communications
http://www.abineau.com
Reply by Jerry Miller●September 19, 20092009-09-19
> Matched filtering should eliminate the DC as well as the AC.
How nice!
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Bret Cahill●September 19, 20092009-09-19
> > If the noise includes some DC it seems that a matched filter would
> > treat it as a zero frequency "curve" and eliminate it in the
> > convolution along with all the higher frequency noise.
>
> What noise?
The noise that got into the original signal has some AC and a DC
offset.
Matched filtering should eliminate the DC as well as the AC.
Bret Cahill