文档介绍：The DTMF Detection Group Page 59
A DISCRETE FOURIER TRANSFORM BASED DIGITAL DTMF
DETECTION ALGORITHM
Jimmy H. Beard, Steven P. Given, and Brian J. Young
The Digital Signal Processing Group
Department of Electrical puter Engineering
Mississippi State University
Mississippi State, Mississippi 39762
{beard, given, byoung}***@
ABSTRACT conversion needed to use analog detectors. With the
constant advances in VLSI driving DSP costs
We present a new type of digital Dual-Tone downward, it is economically sound to replace analog
Multifrequency(DTMF) detection scheme based on the detectors with their digital counterparts which are more
Goertzel DFT algorithm. This detection scheme is more reliable, maintenance cost effective, and spatially
robust and cost-effective than conventional analog minimal.
detection techniques. This algorithm is designed to
provide optimal performance and exceed BellCore[2] Several techniques for digital DTMF detection have
specifications for DTMF detection. The problems been used, but most designers have settled on either
associated with closely spaced signal frequencies and digital filtering or discrete fourier transform(DFT)[4]. In
short tone duration are e by proper window and digital filtering, DTMF signals are passed through
frame selection. Adaptive thresholding is provided to digital bandpass filters centered at the signaling
minimize false outputs due to noise and speech. frequencies(shades of analog). The power at each
frequency is then measured repeatedly to detect the
The algorithm was tested with a variety of data DTMF tones. A DSP then interprets and translates them
including speech, music, and DTMF tones. We find that for the proper switching. The DFT also measures signal
this detector is efficient, reliable, and exceeds BellCore power at the signaling frequencies but has the additional
standards. need to check for signals of some minimum duration.
This will help to ensure