Noise Cancelling Possibilies for Bandpass Noise?

> Not automatically, but easily.  The most direct (and safe) way to
>> implement it would be as a bunch of resonant notch filters, cascaded as
>> necessary for rejection and width.  That'd guarantee your "no phase
>> shift in the pass bands", and give you a solution that's a collection
of
>> cookbook answers.

Wouldn't that operate under the assumption that the signal spectrum and
noise spectrum don't overlap?  I didn't get a condition on that one way or
the other from the OP, but I was assuming that they did.

On Thu, 18 Apr 2013 13:07:30 -0500, dszabo wrote:

>> Not automatically, but easily.  The most direct (and safe) way to
>>> implement it would be as a bunch of resonant notch filters, cascaded
>>> as necessary for rejection and width.  That'd guarantee your "no phase
>>> shift in the pass bands", and give you a solution that's a collection
> of
>>> cookbook answers.
> 
> Wouldn't that operate under the assumption that the signal spectrum and
> noise spectrum don't overlap?  I didn't get a condition on that one way
> or the other from the OP, but I was assuming that they did.

The implicit assumption (thank you for making me state it) is either that 
the noise and signal don't overlap, or that the cost of having the noise 
in the signal is greater than the cost of having the signal with a chunk 
of spectrum missing.

The best time to remove noise from a signal is, of course, before it gets 
in.

-- 
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

>On Thu, 18 Apr 2013 13:07:30 -0500, dszabo wrote:
>
>>> Not automatically, but easily.  The most direct (and safe) way to
>>>> implement it would be as a bunch of resonant notch filters, cascaded
>>>> as necessary for rejection and width.  That'd guarantee your "no
phase
>>>> shift in the pass bands", and give you a solution that's a collection
>> of
>>>> cookbook answers.
>> 
>> Wouldn't that operate under the assumption that the signal spectrum and
>> noise spectrum don't overlap?  I didn't get a condition on that one way
>> or the other from the OP, but I was assuming that they did.
>
>
>The best time to remove noise from a signal is, of course, before it gets

>in.
>
>-- 
>My liberal friends think I'm a conservative kook.
>My conservative friends think I'm a liberal kook.
>Why am I not happy that they have found common ground?
>
>Tim Wescott, Communications, Control, Circuits & Software
>http://www.wescottdesign.com



The implicit assumption (thank you for making me state it) is either that 
the noise and signal don't overlap, or that the cost of having the noise 
in the signal is greater than the cost of having the signal with a chunk 
of spectrum missing.

The cost of having the noise in the signal is greater than the cost of
having the signal with a chunk of spectrum missing is indeed the case!

On 4/18/2013 6:28 AM, westocl wrote:
> I have a signal that is the output of a real time system. The system
> performs 'ok' but has a a problem of what i would reduce down to additive
> band limited noise.  Since I know the source (but cant change it) i know
> that it is bandpass noise of spectral bandwith approx .2Fs.
>
> I am not the liberty to delay the signal AT ALL, so throwing a filter at
> the output is out of the question.
>
> My thoughts were that hopefully there could be a way for me to do some
> noise cancelling using my knowlege of the bandlimited nature of the noise
> and its statistics.
>
> Any suggestions?
>
> (I do not want to add much  unwanted noise into an other reigions when
> trying to get mitigate this bandpass noise.)

If both models for signal source and noise source are available, then 
optimal solution is a kind of (possibly nonlinear) Kalman algorithm. By 
definition, this delivers best result within known data and given 
constraints.
Depending on the nature of a problem, this may or may not work. However, 
if this doesn't work, nothing else will.

Q: Why it is impossible to have sex in Red Square in Moscow ?
A: Because every bystander idiot would be trying to give his invaluable 
advice.

Vladimir Vassilevsky
DSP and Mixed Signal Designs
www.abvolt.com