| 摘要 |
PURPOSE:To prevent misequalization due to the deterioration of an S/N, and to facilitate the demodulation of data after the improvement of the S/N by calculating reception quality by the sum of squares of a reference signal and the error signal of an equalizer output, and controlling the update gain of the equalizer when the value of the sum of squares comes larger than a prescribed value, at the time of tap updating and adjusting in a demodulation circuit. CONSTITUTION:At the point of time when the CD signal of a training signal comes to the prescribed tap position of the automatic equalizer 2, the same pattern as the transmitted data of a CD period is outputted from a reference signal generator 5. An error calculation circuit 4 calculates an error ek between the output of the equalizer 2 and the reference signal. Then, if a circuit echor or the like is superposed upon information data, the sum of squares of the error signal comes larger in a reception quality calculation circuit 8, and comes larger than a fixed threshold TR. Owing to this, the selector of an equalizer coefficient control circuit 7 selects '0', and makes the tap update gain into 0. Accordingly, the misequalization at the time of the deterioration of the S/N is prevented. Besides, after a noise is eliminated, the data can be instantaneously restored by updating the equalization.
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