| US 7,555,117 B2 | ||
| Path change detector for echo cancellation | ||
| Seth Suppappola, Tempe, Ariz. (US); and Franklyn H. Story, Chandler, Ariz. (US) | ||
| Assigned to Acoustic Technologies, Inc., Mesa, Ariz. (US) | ||
| Filed on Jul. 12, 2005, as Appl. No. 11/180,004. | ||
| Prior Publication US 2007/0025282 A1, Feb. 01, 2007 | ||
| Int. Cl. H04M 9/08 (2006.01) | ||
| U.S. Cl. 379—406.08 [370/286; 370/289; 379/406.07; 379/413.01; 704/248] | 12 Claims |
| 1. In a telephone including an audio frequency circuit having a first channel, a second channel, and at least one echo canceling
circuit coupled between said first channel and said second channel, the improvement comprising:
a summation circuit having an input and an output in said first channel;
a path change detector coupled to said input and to said output, said path change detector producing a first output signal
when said echo canceling circuit diverges and producing a second output signal otherwise;
wherein said path change detector includes:
a programmable gain amplifier having an input coupled to the output of said summation circuit and an output;
a comparator having a first input coupled to the output of said programmable gain amplifier and a second input coupled to
the input of said summation circuit, whereby said path change detector, in effect, determines whether or not the quotient
of the magnitude of a signal on the output of the summation circuit divided by the magnitude of a signal on the input of the
summation circuit exceeds a threshold.
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