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双音多频(DTMF)信号是音频电话的拨号信号,电话拨号盘上的数字、符号等用音频范围小于3400Hz的8个频率单音成对表示出来。在通信系统中,需要检测这种DTMF信号以确认来电号码。提出了一种基于DSP的DTMF检测方法,当信号存在单音时,经过相对应的DSP的陷阱滤波器能量幅度会大幅衰减,从而可以判断出信号中存在的单音。DTMF具有在基频上有较高能量而在其二次谐波上有较低的能量,根据这个性质,可以准确的检测出DTMF信号。方法实验验证可行,能够准确检测出DTMF信号。
Dual-tone multi-frequency (DTMF) signals are the dialing signals for audio telephones. The numbers, symbols, etc. on the telephone dial are indicated in pairs with 8 frequency tones with an audio range less than 3400 Hz. In communication systems, this type of DTMF signal needs to be detected to confirm the caller ID. A DTMF detection method based on DSP is proposed. When the signal has a single tone, the energy amplitude of the trap filter through the corresponding DSP can be greatly attenuated, so that the tone existing in the signal can be judged. The DTMF has higher energy at the fundamental frequency and lower energy at the second harmonic. According to this property, the DTMF signal can be accurately detected. The method is validated experimentally and can detect the DTMF signal accurately.