| 摘要 |
PURPOSE:To reflect the result of comparison onto the phase control of timing recovery by estimating a peak value of an impulse response from a reception signal from a line equalizer and calculating two mean values averaging the peak for a prescribed period with the self-running period inbetween and recognizing the direction of a frequency error from the comparison result. CONSTITUTION:When an initial pull-in end signal is given, a protection stage number counter 55 of a PLL circuit 5 advances a phase of a recovered clock by a prescribed phase quantity alpha, sends a peak h0(n) of the impulse response at a present point of time calculated by an impulse response arithmetic circuit 3 to an arithmetic result comparator 4 and an averaging section 41 calculates the mean value. When the averaging period is finished, an output of a NOR gate 46 goes to '1', the comparison of the comparator 43 is executed and the result is given to a protection stage number counter 55 of the PLL circuit 5 as a frequency error direction signal. The mean values are compared only once in such a manner to control the protection stage number in response to the frequency error direction. |
