| 摘要 |
PURPOSE:To prevent the erroneous detection of a training signal from being generated, by finding the signal power of the upper limit frequency of a modem signal, the signal power of a carrier frequency, and the signal power from which the components of the upper limit frequency, the carrier frequency, and the lower limit frequency are eliminated, from an input signal, and setting a ratio of each power to all of signal input powers. CONSTITUTION:The signal power B1 from which signal components in the neighborhood of the upper limit frequency(2900Hz), the carrier frequency(1700Hz), and the lower limit frequency(500Hz) of the modem signal are eliminated, is found from the input signal by an upper/middle/lower frequency elimination output means 6. Next, the fact that the output B1 of the upper/middle/lower frequency elimination output means 6 is less than a threshold value (alpha) set in advance, and also, it is less than the ratio (beta) set in advance of the power A1 of the band area of the upper limit frequency(2900Hz), that is, betaA1, and the power Al of the band area of the upper limit frequency(2000Hz) exceeds the ratio (gamma) set in advance of all of the powers C1 of the input signal, that is, gammaC1, is detected by first and second comparators 8 and 9. In such a way, it is possible to evade the erroneous detection of the training signal. |
