[Eeglablist] Phase Shift when using EEGLAB Filters

[Eriksen, Jeff :LPH EEG]

Marco and list,

 

This linear phase response is proper - the use of this filter will
produce the desired effect in the time domain. See an explanation here:

 

http://www.dspguide.com/ch19/4.htm

 

-Jeff Eriksen

 

From: eeglablist-bounces at sccn.ucsd.edu
[mailto:eeglablist-bounces at sccn.ucsd.edu] On Behalf Of Marco Montalto
Sent: Thursday, February 21, 2013 7:58 AM
To: EEGLAB List
Subject: [Eeglablist] Phase Shift when using EEGLAB Filters

 

Dear List,

 

I have a question to ask regarding filters in EEGLAB. I am using Basic
FIR Filter (new) to bandpass filter my data between 0.5 - 30 Hz. I have
read in previous posts that all EEGLAB filters are zero-phase filters.
Yet the resulting Frequency Response Plot shows that there is a phase
shift in the passband. Here is a link to the saved image of the
Frequency Response Plot: 

 

https://www.dropbox.com/s/uwruvr05np9qxq7/untitled.jpg

 

Would anyone know why this is so i.e. why there is this phase shift? And
also ways to overcome this phase shift?

 

Thanks and looking forward to hearing from you.

 

Regards,

Marco Montalto

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