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Topic: Implementing Adaptive Filters in Bioera
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angel61606



Joined: Jul 8, 2020
Posts: 75

PostPosted: Nov 7, 2021 9:33 AM    Post subject: Implementing Adaptive Filters in Bioera

Hi Jarek
As you know in some cases of signal processing we get to the point where it is required to go for more complex versions of filtering such as adaptive filtering. using them is inevitable sometimes, so i was wondering if i can somehow use these kinds of filtering in bioera? if yes how is it possible. i would really appreciate it if u help me out on this matter coz i am really struggling in my new project.
jarek



Joined: Oct 22, 2007
Posts: 930

PostPosted: Nov 7, 2021 2:41 PM    Post subject:

What do you mean by "adaptive" filtering. Is this an ability to change filter properties during processing? If so, then this is possible with PropertySetter, although current state of the filter must be reset (reinitialized) in order to make such change.
angel61606



Joined: Jul 8, 2020
Posts: 75

PostPosted: Nov 8, 2021 2:39 PM    Post subject:

what I meant by adaptive filtering is the generic term people use for those filters. the filters which adapt their parameters automatically for various purposes, in my case for noise cancellation. Thus no. i dont want to change a simple filter properties using a property setter . what i want is a whole different story.


let me explain why i am looking for such filters , practically to remove main power noise (50HZ) from my data an ideal notch filter (which just removes a very narrow band around 50Hz ) was not enough , so i had to expand the stop band to 10 hz to fully remove the effect of main power noise so i had to use (45-55 Hz )band stop filter. this way i could remove the effect of noise from my signal but i lost a great deal of information of my signal as well. this is so unpleasant and unacceptable. so i shifted my attention to adaptive filtering.

I noticed some of the users here mentioned a different implementation of notch filter suggested by GMArtin, http://www.bioera.net/support/viewtopic.jsp?id=551 . i am curious if it could help me! how can i get to information about that implementation?


I am open to any suggestion regarding this issue.
jarek



Joined: Oct 22, 2007
Posts: 930

PostPosted: Nov 8, 2021 3:08 PM    Post subject:

I don't have much experience with Notch filters so can't help.

My understanding is that it makes sense to use Notch directly on the device in order to prevent signal saturation or distortion (if out of range). Many devices have this option. But if that signal has arrived fine to PC, I don't see much point of filtering that out (for most use cases) since a typical bandpass filters (like Alpha) are not affected. If you do use very close frequency around 50Hz then yes, I see how this can be affected, but I would probably try to filter in the useful data rather than filter out the interference.
Gmartin3



Joined: Oct 19, 2021
Posts: 8

PostPosted: Dec 28, 2021 1:33 PM    Post subject:

I just saw your post

I have used the notch filter idea for=several years. If the details have not been posted, here they are.
I create a filter fo 58-62 hz. I connect the signal from the amp to In 1 of expression evaluator. I connect the output of th 58-62 filter to In2. Expression is In1-In2. This has cleaned up the signal nicely with no noticeable delay or other distortions
angel61606



Joined: Jul 8, 2020
Posts: 75

PostPosted: Jan 5, 2022 6:47 AM    Post subject:

Hi Gmartin

Thanks for your explanation, I really appreciate it. I am wondering why u simply didn't use a band stop as a notch filter ? what are the advantages to use a bandpass and then subtract it from the signal?
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