Derivate a signal with staircase

Hi everyone

I have a signal like this, the sampling rate is low then i get the signal with a staircase.

The problem is that i want to derive it. 2 times! If i derive this signal i get a very bad derivative of course, and more the 2nd derivative.

I tryed to make it smoother with a simple cubic spline but i always have a bad derivate signal.

Any idea on how to make it smooth and well derivable?

Thanks!!!

Answer 1

[Jan]

A Savitzki-Golay-filter might be sufficient for your data: The local neighborbood is approximated by a polynomial, such that the derivatives are easy to calculate:

• https://www.mathworks.com/matlabcentral/fileexchange/68342-savitzky-golay-differentiation-fir-filter-generalized
• https://www.mathworks.com/matlabcentral/fileexchange/63011-savitzky-golay-differential-filter-for-spectral-data
• https://www.mathworks.com/matlabcentral/fileexchange/7003-adaptive-degree-polynomial-savitzky-golay-filter-for-data-differentiation

[Stefano Massardi]

It gives me something like this. many samples are actually replicated in the horizontal part, i dont' know if this influences