cut off frequency

Started by vani chezhiyan March 25, 2004

hi all,

i'm doing a project in preprocesing biosignals.

if i'm given with a signal,how will i find out the cut off frequency?

is it possible only by looking into the power spectrum.is there any formula(given only the sampling frequency)?

kindly help.

 

thanx in advance

 



Hi Vani,
 
Most biosignals tend to be low frequency in nature, making them an interesting challenge to process.  Because they tend to be low frequency, they can very easily be corrupted by unwanted interference e.g. mains supply or other biosignals.  As in most things, you must have a good idea of what you are trying to achieve.  Preprocess a signal, for what purpose?
 
I suggest you use the SPTOOL feature of Matlab to get started with, as this requires little knowledge of Matlab.  This will allow you to view your data, look at the spectrum and apply some filtering.    One point to remember you must know the sampling frequency of your data acquisition, as this will determine all the initial design parameters for your signal processing.
 
As for cut-off frequency, if this is in relation to a filter you want to design, you probably need to look at the unprocessed spectrum first to see where the activity is present.
 
As was suggested in a previous posting to this group, the more information that's provided, the better the response.
 
Best regards,
 
Jeff
 
======================
Jeff Winter
Snr Design Engineer
Aeroflex
www.aeroflex.com
 
 -----Original Message-----
From: vani chezhiyan [mailto:v...@yahoo.com]
Sent: Thursday, March 25, 2004 9:36 AM
To: m...@yahoogroups.com
Subject: [matlab] cut off frequency

hi all,

i'm doing a project in preprocesing biosignals.

if i'm given with a signal,how will i find out the cut off frequency?

is it possible only by looking into the power spectrum.is there any formula(given only the sampling frequency)?

kindly help.

 

thanx in advance

 



Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer.  You need to do a "reply all" if you want your answer to be distributed to the entire group.

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Hi Vani,
 
Most biosignals tend to be low frequency in nature, making them an interesting challenge to process.  Because they tend to be low frequency, they can very easily be corrupted by unwanted interference e.g. mains supply or other biosignals.  As in most things, you must have a good idea of what you are trying to achieve.  Preprocess a signal, for what purpose?
 
I suggest you use the SPTOOL feature of Matlab to get started with, as this requires little knowledge of Matlab.  This will allow you to view your data, look at the spectrum and apply some filtering.    One point to remember you must know the sampling frequency of your data acquisition, as this will determine all the initial design parameters for your signal processing.
 
As for cut-off frequency, if this is in relation to a filter you want to design, you probably need to look at the unprocessed spectrum first to see where the activity is present.
 
As was suggested in a previous posting to this group, the more information that's provided, the better the response.
 
Best regards,
 
Jeff
 
======================
Jeff Winter
Snr Design Engineer
Aeroflex
www.aeroflex.com
 
 -----Original Message-----
From: vani chezhiyan [mailto:v...@yahoo.com]
Sent: Thursday, March 25, 2004 9:36 AM
To: m...@yahoogroups.com
Subject: [matlab] cut off frequency

hi all,

i'm doing a project in preprocesing biosignals.

if i'm given with a signal,how will i find out the cut off frequency?

is it possible only by looking into the power spectrum.is there any formula(given only the sampling frequency)?

kindly help.

 

thanx in advance

 



Note: If you do a simple "reply" with your email client, only the author of this message will receive your answer.  You need to do a "reply all" if you want your answer to be distributed to the entire group.

_____________________________________
About this discussion group:

To Join:  m...@yahoogroups.com

To Post:  m...@yahoogroups.com

To Leave: m...@yahoogroups.com

Archives: http://www.yahoogroups.com/group/matlab

More DSP-Related Groups: http://www.dsprelated.com/groups.php3



hi all,

i'm doing a project in preprocesing biosignals.

if i'm given with a signal,how will i find out the cut off frequency?

is it possible only by looking into the power spectrum.is there any formula(given only the sampling frequency)?

kindly help.

 

thanx in advance