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I have one question about digital correction of signal after RC filter which is high-pass.

Let me explain detail.

I have one simple signal conditioner. It has RC filter on the signal input with cut-off frequency equals 1.3 Hz. It means that after this RC filter my signal has lower amplitude from 1.3 Hz to approximately 15 Hz. After ADC I get this signal on my computer in digital form. After that I use Fourier transform.

Unfortunately, I need correct amplitude information in range 2-20Hz. So I need correct amplitude of signal in that range by digital transformations.

Can I do this? Is it normal practice?

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Yes, this seems like a normal thing to do. However, note that the signal-to-noise ratio will be degraded in the 1.3 Hz to 15 Hz band. Your signal will be smaller but the quantization noise of the ADC will stay the same.

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  • $\begingroup$ Thank you for answer! But which formula i should use for correction? Can you give any links? $\endgroup$
    – erix
    Commented Feb 26, 2015 at 11:42
  • $\begingroup$ From your post, you already have the Fourier transform of the signal S(\omega) after the RC filter. To recover the signal before the filter, just divide by the transfer function of the RC filter, f(\omega) = i \omega R C/(1+i \omega R C). See en.wikipedia.org/wiki/RC_circuit for more details. $\endgroup$
    – Dave Kielpinski
    Commented Feb 26, 2015 at 11:53

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