| 摘要 |
PROBLEM TO BE SOLVED: To set a data threshold voltage to a center voltage of a high voltage range and a low voltage range of a 4 PAM signal.SOLUTION: An error rate measuring apparatus comprises: an A/D conversion part 4 that converts a 4 PAM signal having a high voltage range H1, a middle voltage range H2, and a low voltage range H3 into an AD value; a threshold voltage variable part 3 that varies a data threshold voltage Vth by a predetermined step; saturation voltage detection means 6b that detects an upper limit data threshold voltage saturated by the AD value as an upper limit voltage of the high voltage range H1 and a lower limit data threshold voltage Vth saturated by the AD value as a lower limit voltage of the low voltage range H3; and center voltage calculation means 6c that calculates a center voltage of the middle voltage range H2 by using the upper limit voltage of high voltage range H1 and the lower limit voltage of low voltage range H3, and calculates the center voltage of high voltage range H1 or the center voltage of low voltage range H3 by using the center voltage of the middle voltage range H2 and the upper limit voltage of high voltage range H1 or the lower limit voltage of the low voltage range H3.SELECTED DRAWING: Figure 1 |
