Invention Grant
- Patent Title: System and method for precise DTMF signal detection
- Patent Title (中): 用于精确DTMF信号检测的系统和方法
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Application No.: US09407829Application Date: 1999-09-28
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Publication No.: US06560331B1Publication Date: 2003-05-06
- Inventor: Todor Cooklev , Mark Gray
- Applicant: Todor Cooklev , Mark Gray
- Main IPC: H04M300
- IPC: H04M300

Abstract:
A method and system for facilitating the detection of DTMF tones is disclosed. The method is based on detecting two tones using a modified nonuniform discrete Fourier transform that includes a phase correction term for each DTMF tone and harmonic. The disclosed method is employed by a DTMF detector that includes a sampling module, a computation module, an analysis module, and a decode module. The sampling module samples an input signal from a communication network at a rate sufficient to avoid data loss. The sample signal is then placed through a modified DFT which is more precise than filters or analog devices, particularly those utilizing a Goertzel algorithm. The computation module implements a fast recursive algorithm for completing the necessary computations. The analysis module checks for the present of energy level peaks at the DTMF tones and their harmonics. Once a DTMF signal is verified to contain a DTMF tone, the decode module transmits the,number, letter, or symbol to an interface.
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