Background Correction in Frequency-Domain Measurements

If the background is larger, its significance is greater, but it can also be measured with higher precision. 

A data file corrected for background is created by the following procedure. Let 

In these eqmmons is the fraction of the total due to the backgroimd. and and m are the correct foase and modulafion values in the alienee of background. The corrected vahies of Nm and Dm are ven by 

The lower panels show the deviations between the data and the fitted curves. In this case the deviaticns are presented ui units of degrees and percent modulafion. For calculation of xi the standard errors were taken as 5 = 0.2 and 5m = 0.005. Die fact that the values of are dose to unity reflects an iqi vopriate chdoe frv the values of 5 and 5m. In analysis of the FDdata. one cannot rely on the absolute values of xl but rather uses the ratio of values 

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