Efficient digital ITU-compliant zero-buffering DTMF detection using the non-uniform discrete fourier transform

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dc.contributor.assigneeThe Board of Regents of the University of Texas System
dc.creatorMatthew D. Felder
dc.creatorJames C. Mason
dc.creatorBrian L. Evans
dc.date.accessioned2019-10-23T19:32:55Z
dc.date.available2019-10-23T19:32:55Z
dc.date.filed1998-04-03
dc.date.issued2002-04-09
dc.description.abstractComputationally efficient DTMF detection methods and apparatus are presented that meet all of the ITU recommendations using the modified non-uniform DFT. The system of the present invention employs a high band filter block and two low band filter blocks to detect power at the 8 DTMF tones. The frame length of the high band filter blocks is one half the length of the low band filter blocks. The frame lengths are chosen to meet the ITU frequency selectivity requirements for all DTMF frequencies. The frames of the two low band filter blocks are staggered to produce outputs alternately, and are aligned with respect to the frame of the high band filter block to produce low band filter block outputs that coincided with the high band filter block outputs without the need for signal buffering. A system of power level tests are employed in conjunction with a system of timing tests to ensure that all ITU timing and frequency constraints are met. The present invention requires no buffering of input samples, and can perform DTMF decoding of 24 telephone channels of a T1 time-division multiplexed communication line, using a single fixed-point commercially available digital signal processor.
dc.description.departmentBoard of Regents, University of Texas System
dc.identifier.applicationnumber9054872
dc.identifier.patentnumber6370244
dc.identifier.urihttps://hdl.handle.net/2152/77121
dc.identifier.urihttp://dx.doi.org/10.26153/tsw/4210
dc.publisherUnited States Patent and Trademark Office
dc.relation.ispartofUniversity of Texas Patents
dc.relation.ispartofUniversity of Texas Patents
dc.rights.restrictionOpen
dc.rights.restrictionOpen
dc.subject.cpcH04M7/1295
dc.subject.cpcH04Q1/4575
dc.subject.uspc379/386
dc.subject.uspc379/283
dc.titleEfficient digital ITU-compliant zero-buffering DTMF detection using the non-uniform discrete fourier transform
dc.typePatent

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