Help for baseline drift removal/correction

Question

I have signal as seen in the picture. It has high frequency noise and drifting baseline. I am able to remove the noise in MATLAB but I am not sure what can I do about the drift.

I would like the signal to have a stable baseline. Any help or hints on how I can do that would be most helpful.

Thanks

Answer 1

Like I already mentioned in the comment, you might find MATLAB's detrend function useful. Generally it is useful for removal of linear (or piecewise linear) trend:

y = detrend(x);

Another solution, that should work in your case, is to use the polynomial fitting. This will remove the non-linear trend (providing you want that). A minimal code example:

% vectors t,x are given (time and the signal)
degree = 5; % to be adjusted
[p, S, mu] = polyfit(t, x, degree);
xp = polyval(p, t, [], mu);
y = x - xp;

Personally I do not recommend any Moving Average filtering, since it is introducing delay and can distort your signal.

Answer 2

A drifting baseline to me looks like a displacement from zero by the mean amplitude.

• From a stats point of view, you will want compute the rolling mean and subtract.
• From a signals point of view, this problem is a DC offset, and can be corrected with a high pass filter, with a very low cutoff, that essentially removes this low frequency amplitude modulation. There are a number of prior discussion here, and implementations. If you're in MATLAB, detrend can be useful as already mentioned.