Millstrum Analysis

ROTATE Plus has a feature called the Millstrum Analysis. This analysis is a variation of the Cepstrum analysis and helps you to identify families of harmonics which are present in your data.

In the data displayed in this figure, there are two families of harmonics present, at orders .85 and .79. However, from the raw data displayed, it is very difficult to determine this without the use of sideband cursors. Sideband cursor, however, are limiting when data is noisy or, as with the waterfall in Figure xx, when a number of high amplitude orders obscure the harmonic families.

In this case, a Millstrum analysis is necessary. The order plot displayed in the second figure was generated using the Millstrum analysis. Now it is quite easy to see the harmonic families at order .85 and .79. There are also modulations of the harmonics appearing at orders .42 and .39.