Multi-frequency signal detector and classifier

Apparatus for detecting and classifying signals on a source line that are the additive combination of a few constant-amplitude sinusoidal components, herein called N-tones, comprising:

• (a) a component isolation filter having an input coupled to said source line and operative to reject extraneous signal components and to separate data on said source line into one or more separate output streams;
• (b) a block segmenter coupled to each of said output streams for producing blocks of successive data samples;
• (c) a component magnitude estimator coupled to the output of each said block segmenter and operative for estimating the magnitude of data within each said block from each said output stream;
• (d) a frequency estimator coupled to the output of each said block segmenter and operative for identifying the dominant spectral components within each said block from each said output stream, the number of dominant spectral components identified for each said block from each said output stream being known by design from the nature of the N-tones being detected and the distribution of signal components among said output streams;
• (e) a periodically-reconfigured notch filter coupled to the output of each said block segmenter and coupled to the output of the corresponding frequency estimator and operative for removing the identified dominant spectral components from each said block from each said output stream without regard to previous blocks;
• (f) a residual magnitude estimator coupled to the output of said notch filter and operative for estimating the magnitude of data within each said block from each said output stream after the identified dominant spectral components have been removed;
• (g) a block classifier coupled to outputs of all component magnitude estimators, all frequency estimators and all residual magnitude estimators, and operative to test if the signal on said source line has the requisite properties of tonal purity, absolute component magnitude, relative component magnitude and component frequency, the output of said block classifier providing an indication of the class of N-tone that is present during times when said requisite properties are satisfied, the output of said block classifier also providing an indication of classification failure during times when said requisite properties are not satisfied;
• (h) a timing classifier coupled to the output of said block classifier operative for testing the duration of a candidate N-tone for conformance with application-specific requirements regarding signal persistence and longevity, and other signal timing restrictions as required by the application;
• and
• (i) means for coupling a subset of the output of said component magnitude estimators to said timing classifier so that refined estimates of signal duration may be computed by said timing classifier.

A method for detecting and classifying signals on a source line that are the additive combination of a few constant-amplitude sinusoidal components, herein called N-tones, comprising:

• (a) rejecting of extraneous signal components from the said source line signals, and producing one or more separate output streams:
• (b) establishing blocks of successive data samples from each said output stream;
• (c) estimating the magnitude of data within each said block from each said output stream;
• (d) identifying the dominant spectral components within each said block from each said output stream;
• (e) removing the identified dominant spectral components from each said block from each said output stream without regard to previous blocks;
• (f) estimating the magnitude of data within each said block from each said output stream after removal of the identified dominant spectral components;
• (g) testing the magnitude estimates that were obtained both before and after removal of the identified dominant spectral components, thereby partially ascertaining if the signal on said source line has the requisite properties of an N-tone;
• (h) testing the frequencies of the identified dominant spectral components, thereby partially ascertaining if the signal on said source line has the requisite properties of an N-tone;
• (i) deriving a running estimate of the duration of time that the signal on said source line is an N-tone;
• (j) deriving a running estimate of the duration of time that the signal on said source line is not an N-tone;
• (k) testing the durations of candidate N-tones and intervening non-N--tone segments for conformance with signal persistence and longevity requirements.