filtering of noise signal

how to filter a noise signal using iir filter coefficients-- cybyshev or
bessel,
band is between 45hz to 65hz, sampling frequency 1000hz


if 240 hz pure signal
noise +signal =270 hz---->  iir filter----->240hz

On 05/23/2011 04:04 AM, rashmi venugopal wrote:
> how to filter a noise signal using iir filter coefficients-- cybyshev or
> bessel,
> band is between 45hz to 65hz, sampling frequency 1000hz
>
>
> if 240 hz pure signal
> noise +signal =270 hz---->   iir filter----->240hz

Come again?

Are you asking how to make a low pass filter with a bandwidth between 45 
and 65Hz, are you asking how make a bandpass filter centered on 240Hz, 
are you setting conditions and asking for a filter design to do the 
work, or are you doing something yet again?

Try again with more words, and note that in frequency domain analysis, 
frequencies of signals (and noise) is invariant, so it is very difficult 
to come up with an interpretation of

"noise +signal =270 hz---->   iir filter----->240hz"

that makes sense.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

On 23.5.11 6:05 , Tim Wescott wrote:
> On 05/23/2011 04:04 AM, rashmi venugopal wrote:
>> how to filter a noise signal using iir filter coefficients-- cybyshev or
>> bessel,
>> band is between 45hz to 65hz, sampling frequency 1000hz
>>
>>
>> if 240 hz pure signal
>> noise +signal =270 hz----> iir filter----->240hz
>
> Come again?
>
> Are you asking how to make a low pass filter with a bandwidth between 45
> and 65Hz, are you asking how make a bandpass filter centered on 240Hz,
> are you setting conditions and asking for a filter design to do the
> work, or are you doing something yet again?
>
> Try again with more words, and note that in frequency domain analysis,
> frequencies of signals (and noise) is invariant, so it is very difficult
> to come up with an interpretation of
>
> "noise +signal =270 hz----> iir filter----->240hz"
>
> that makes sense.


We should actually pose some questions to the OP. It seems
that he does not have the slightest clue.

1. Homework, who's the professor?

2. If a real construction problem, is the purpose to notch
    out power line disturbances? Have the methods to keep
    out the undesired noise coming into the electronics
    tried at all?

3. Should the processing change the frequency of the signal,
    and how?

-- 

Tauno Voipio