Detrending of non-stationary noise data by spline techniques

An off-line method of detrending non-stationary noise data is given. It uses a least-squares spline approximation of the noise data with equally spaced breakpoints. Subtraction of the spline approximation from the noise signal at each data point gives a residual noise signal. The method acts as a high-pass filter with very sharp frequency cut-off. The cut-off frequency is determined by the breakpoint distance. The steepness of the cut-off is controlled by the spline order