Backward Linear Prediction

Backward Linear Prediction replaces data points at the beginning of the FID that may have been poor due to acquisition issues or background resonances. It is often helpful in spectra with very wide spectral widths in Hz, spectra with background signals such as the signal from the teflon in the probe in F19, or some spectra with fast relaxing nuclei.

The Linear Prediction menu is located under the Processing tab then Zero-Filling/LP. Zero-Filling is discussed here:
Zero-Fill

Forward Linear Prediction is discussed here:
Forward Linear Prediction


1) To accomplish Backward Linear Prediction, select Backward in the lower left box below the Zero-Fill.

2) In the Linear Prediction box on the lower left, the From is where to start predicting points, the To is the amount of points to predict to, the Method is the way the prediction is accomplished, the Basis points are the amount of points being used to predict, and the Coefficients are the amount of coefficients being used for the prediction.

From = usually the prediction is started at the first acquired data point = 1.

To = the amount of points to predict to, normally minimize this as this the number of acquired points to replace, typically between 5 and 10 .

Method = Typically Toeplitz is best, but there are other options.

Basis Points = Amount of points acquired used to predict the points. Normally, this is all acquired points (Original), but depending upon how fast the relaxation of the nuclei are and the amount of acquired points are, a lower number may work better. For example, if the acquired data points were substantially beyond the end of the decay of the FID, using more points would not help in the prediction.

Coefficients = Typically the default value is fine.

3) Since the backward linear prediction is used to eliminate data points at the beginning of the FID that are either incorrect in amplitude or decay rapidly, to see the effectiveness of it, look at the baseline after application. Backward linear prediction should limit baseline roll.