IEEE Trans. on Signal Processing, vol. 48, no. 3, pp. 911-916, Mar. 2000

A Low-Complexity ITU-Compliant Dual Tone Multiple Frequency Detector

Amey A. Deosthali (1), Shawn R. McCaslin (2), and Brian L. Evans (3)

(1) Schlumberger Technology Corporation, 110 Schlumberger Dr., MD4, Sugar Land, TX 77478
deosthali@sugar-land.spc.slb.com

(2) Cicada Semiconductor, Barton Oaks Plaza One, 901 South Mopac Expressway, Austin, TX 78746.
srm@cicada-semi.com

(3) Department of Electrical and Computer Engineering, Engineering Science Building, The University of Texas at Austin, Austin, TX 78712-1084 USA
bevans@ece.utexas.edu

Paper - Matlab code for 8-bit implementation

Abstract

We present the first dual tone multiple frequency (DTMF) signal detector that meets the International Telecommunications Union (ITU) Q.24 DTMF standard when implemented on an 8-bit microcontroller. Key innovations include the use of adaptive notch filters and sophisticated decision logic. The DTMF detector is also well-suited for a multi-channel digital signal processor implementation.

Errata

In the paper, equation (2) is written as
^              ^                  ^   
F(n) = alpha * F(n-1) + (1-alpha)*F(n)
It should have been
^              ^                      
F(n) = alpha * F(n-1) + (1-alpha)*F(n)
Here, F(n) is the output of the two-tap averaging filter (first stage of estimator) and
^
F(n)
is the output of the first-order IIR filter (second stage of estimator).


Last Updated 11/04/01.