| 摘要 |
PURPOSE: To detect the existence of a repeat sequence by estimating the existence of a training sequence by the signal level and the error level of a demodulation signal and comparing it with a reference. CONSTITUTION: A demodulation input signal of a sample output from the demodulator of an orthogonal amplitude modulation modem receiver after a low pass filter is caused to pass a delay circuit, and the absolute distance between two samples Big.dif and Small.dif is calculated. It is compared with a specific reference value based on the noise level and the signal level by a comparator; and if it is within the reference value, the existence of a training sequence P.2 is recognized. Thus, a repeat sequence is detected based on pattern recognition of a base band signal to perform reliable detection with simple device and means. |
