DTMF detection having sample rate decimation and adaptive tone d

Details DTMF detection having sample rate decimation and adaptive tone d DTMF detection having sample rate decimation and adaptive tone d

1991-11-25

1995-02-21

Dwyer, James L.

Telephonic communications

Supervisory or control line signaling

Signal receiver

379283, 379282, 3701103, H04M 150

Patent

active

053923480

ABSTRACT:
A method of dual-tone multifrequency (DTMF) detection which decimates and adaptively filters an input signal is provided to efficiently detect a presence of a DTMF signal. The input signal is provided to a half-band filter (14) to be decimated in frequency in accordance with Nyquist's theory. A decimated input signal is subsequently processed to form a low frequency component signal and a high frequency component signal. The low frequency component signal is again decimated by a decimator (24). The decimated low frequency component signal and the high frequency component signal are each filtered by an adaptive fir filter (22, 26) to provide a first and a second frequency parameter and a first and a second gain factor, respectively. The first and second frequency parameters and the first and second gain factors are then tested by a tone identifier (28) to determine if the input signal includes a valid DTMF signal.

REFERENCES:
patent: 3571522 (1971-03-01), Cox
patent: 4999830 (1991-03-01), Agazzi
patent: 5144626 (1992-09-01), Funatsu et al.
patent: 5214693 (1993-05-01), Chujo
"AN-1 Dual-Tone Multifrequency Receiver Using The Digital Signal Processor" published by Western Electric in Jul., 1981, pp. 1-13.
"Dual-Tone Multifrequency Receiver Using the WE DSP32 Digital Signal Processor" published by AT&T in 1988, pp. 1-15.
"Efficient DSP Based Detection of DTMF Tones" written by R. A. Valenzuela and published in the IEEE Global Telecommunications Conference & Exhibition proceedings, pp. 1717-1721.
"On The Detection and Tracking of A Class of Narrowband Sources" by N. Ahmed, D. Hush, S. Park G. R. Elliott, and R. J. Fogler and published in the Proc. of Amer. Control Conf. of 1984, pp. 210-212.

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