| 摘要 |
A dual-tone detection system comprises a receiver and a digital-signal processor. The digital-signal processor comprises an arithmetic-logic unit as well as window, automatic-gain control, first filter, second filter and determination modules. The window module generates a representation of the input signal. The automatic-gain control module generates a scaled representation so the tones are at a desired power level. The first filter centered about a first frequency generates a first measurement. The second filter centered about a second frequency generates a second measurement. The arithmetic-logic unit uses an equation that models a power relationship between the first and second filtered tones to generate adjusted first and second measurements, respectively. The determination module compares each of the adjusted first and second measurements with a threshold value to identify when the input signal contains the low-frequency and high-frequency tones associated with a particular DTMF symbol. |
