Multiple-frequency signal classification through use of a second-order statistic

摘要

A multi-frequency (also known as multiple-frequency) signal, such as a dual-tone signal, can be a repeating signal that indicates a character designated on a keypad. The signal can be processed such that the character is identifiable. This processing can include using first and second-order statistics of the signal to determine an estimated average frequency of the signal. A table can be accessed that lists individual characters of the keypad and specific average frequency values can be associated with the individual characters. The specific average frequency value that is closest to the estimated average frequency can be identified and the character associated with this closest specific average frequency value can be appointed as the character indicated by the signal. Thus, the multi-frequency signal can be classified as communicating the appointed character.

主权项

1. A signal processor unit, that is at least partially hardware, comprising:
a first-order calculation component configured to calculate a first-order statistic of a multi-frequency signal that includes a high frequency of the multi-frequency signal and a low frequency of the multi-frequency signal; a second-order calculation component configured to calculate a second-order statistic of the multi-frequency signal that includes the high frequency of the multi-frequency signal, the low frequency of the multi-frequency signal, and an estimated average frequency of the multi-frequency signal; an identification component configured to identify the estimated average frequency of the multi-frequency signal through performance of a subtraction with the first-order statistic and the second-order statistic that isolates the estimated average frequency from the multi-frequency signal; a determination component configured to determine a character associated with the multi-frequency signal through use of the estimated average frequency; and an output component configured to output the character after the character is determined.