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Re: filtering out harmonic trend
From: |
Francesco Potorti` |
Subject: |
Re: filtering out harmonic trend |
Date: |
Mon, 17 Dec 2007 15:08:13 +0100 |
>> I have a 200,000 samples measurement, which is a sort of noise with
>> bandwidth in the order of the inverse of 500 samples. Superimposed to
>> this noise there is a very slow sinusoid with a period of about
>> 300,000
>> samples. This means that my measurements do not even see a complete
>> cycle of this sinusoid.
>>
>> I want to estimate the sinusoid (in order to remove it from the
>> measurement). So I need some sort of very-low pass filter. However,
>> usign a simple causal low-pass filter would give me a delayed output.
>> Can anyone suggest some keyword for a noncausal filter to look for? I
>> guess that it could be simple, because the bandwidths of signal and
>> noise are so far away each other.
>
>If the low-frequency signal is a 'clean' sinusoid, then I'd try
>fitting a sinusoid to the data, and then subtract this sinusoid from
>the data.
After some experimentation, it turns out that my low-frequency signal
is not a sinusoid. So I stuck with filtfilt. Now, I am deciding what
filter to use and how to choose its parameters.
Thank you
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