Extract a certain frequency from the signal

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Joana Silva 2017-10-2

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https://ww2.mathworks.cn/matlabcentral/answers/359296-extract-a-certain-frequency-from-the-signal

回答： Star Strider 2017-10-2

Hi everybody! I am processing some data and because I am measuring pore pressure in water, I always have some waves from the initial disturbance. I have a reference signal and I want to remove the waves from the other signals. The plan is to find out the frequency associated to this waves from the reference signal and extract this frequency from the other signals. I already did this, f=0,1611 Hz. Now the question is, how can I subtract this frequency from the other signals? Thanks in advance! Joana

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Rik 2017-10-2

What have you tried so far? If you have the signal processing toolbox, there are several functions that could do this.

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Answer 1

Star Strider 2017-10-2

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There are several options, all involving filtering the 0.1611 Hz frequency out of your signal.

A good place to start is Remove the 60 Hz Hum from a Signal (link). Change the frequency of the ‘notch’ in the demonstration code to 0.1611 Hz, and experiment to get the result you want. This may not be as straightforward as it first appears, depending on your sampling frequency. Desigining stable, reliable, low frequency filters with a high samping frequency can be a challenge.

I prefer using freqz to analyse the filter, and the filtfilt function to do the actual filtering.