Method for determining a periodic pattern in a line spectrum

Claim 1

A method for determining a periodic pattern in a line spectrum comprising the steps of: forming an original amplitude line spectrum having a reference line and a plurality of spectral lines which are contiguous to the reference line; forming a plurality of intervals in the line spectrum by combining a first predetermined number of contiguous spectral lines of the original amplitude line spectrum; determining a mean value for each respective interval based on an amplitude of each spectral line combined to form the respective interval; filtering the amplitude of each spectral line of the original amplitude line spectrum with a predetermined factor; normalizing the filtered amplitude of each spectral line of each respective interval with the associated mean value of the respective interval; categorizing the normalized amplitudes of the spectral lines into a plurality of overlapping normalized amplitude categories; determining a periodic complement to each respective spectral line which is a continuation line that is at least contiguous to the reference line for each spectral line and forms a line pair with the respective spectral line; categorizing each line pair in a relevance category as a function of a predetermined combination of the normalized amplitude categories, each relevance category having a predetermined relevance value range; determining a relevance value for each line pair; determining a maximum relevance value for all line pairs associated with one spectral line; associating the determined maximum relevance value with the spectral line; forming a residual amplitude line spectrum from spectral lines having an associated relevance value which is greater than a predetermined threshold value; histogramming the original amplitude line spectrum to determine the number of continuation lines associated with each respective spectral line of the residual amplitude line spectrum; determining the spectral line having the greatest number of continuation lines from the histogram; and determining a modulation frequency of the periodic pattern based on the difference in frequency between the spectral line having the greatest number of continuation lines and the reference line.

Claim 2

A method for determining a periodic pattern in a line spectrum comprising the steps of: forming an original amplitude line spectrum having a reference line and a plurality of spectral lines which are contiguous to the reference line; forming a plurality of intervals in the line spectrum by combining a first predetermined number of contiguous spectral lines of the original amplitude line spectrum; determining a mean value for each respective interval based on an amplitude of each spectral line combined to form the respective interval; filtering the amplitude of each spectral line of the original amplitude line spectrum with a predetermined factor; normalizing the filtered amplitude of each spectral line of each respective interval with the associated mean value of the respective interval; categorizing the normalized amplitudes of the spectral lines into a plurality of overlapping normalized amplitude categories; determining a periodic complement to each respective spectral line which is a continuation line that is at least contiguous to the reference line for each spectral line and forms a line pair with the respective spectral line; categorizing each line pair in a relevance category as a function of a predetermined combination of the normalized amplitude categories, each relevance category having a predetermined relevance value range; determining a relevance value for each line pair; determining a maximum relevance value for all line pairs associated with one spectral line; associating the determined maximum relevance value with the spectral line; forming a residual amplitude line spectrum from spectral lines having an associated relevance value which is greater than a predetermined threshold value; histogramming the original amplitude line spectrum to determine the number of continuation lines associated with each respective spectral line of the residual amplitude line spectrum; determining the spectral line having the greatest number of continuation lines from the histogram; and determining a modulation frequency of the periodic pattern based on the difference in frequency between the spectral line having the greatest number of continuation lines and the reference line.