| 摘要 |
PURPOSE:To eliminate the deterioration in the efficiency of data transmission and to attain measurement without transmission and reception of information to/from a terminal device by measuring the phase jitter during the initial training. CONSTITUTION:Only the positive Nyquist frequency component is extracted from a demodulated output during the period of an initial training signal by delay devices 26, 27, coefficient devices 28, 29 and an adder 30 in the data transmission system using two kinds of alternate patterns as the training signal. This output is inputted to a detector 31, a counter 32 and an oscillator so as to obtain an interval of zero crossings and the DC component of this output is eliminated by a subtractor 34 and a delay device 35. The maximum/minimum values of the subtractor 34 and the delay device 35 are obtained by switches 36, 39, delay devices 37, 40 and comparators 38, 41, and a subtractor 42 calculates the difference so as to obtain the phase jitter. On the other hand, an output of the subtractor 42 is made effective by a detector 43, a timer 44 and a switch 45 only during the period of the training signal. |
