| 术语 | digital sum |
| 释义 | digital sum 数字和;［数位和］ A concept used in connection with the study of signals produced by various codes. The pulse levels in the signal are given signed values, so that in a typical three-level line signal a positive pulse would have the value +1, space would be represented by 0 and a negative pulse by-1. The digital sum is then the sum of all the pulse valves from some arbitrary time origin up to the instant under consideration. It is clear that its value at any instant will be equal to the difference in the number of positive and negative pulses that have been transmitted, and that refore a measure of the accumulated imbalance of the signal. In order to restrict the amount of low-frequency energy in the signal, the running digital sum must be kept within low limits and many codes have been devised to satisfy this requirement. 一种对各种码产生的信号进行研究中所使用的概念。信号中的脉冲电平被赋予带符号的 值,因此,在一个典型三电平信号中,正脉冲电平具有+1值,空位用0表示,负脉冲电平用-1表 示。数字和是所有从某个任意时间为起点,到所考虑的时刻为止的所有脉冲的和。很清楚, 在任一时刻的值,等于传送的正负脉冲个数之差。因此它是一个信号累积不平衡度的量度。 为了限制信号中低频能量的量,该数字和必须保持在低的限度之内,已设计出许多码满足 这一要求。 |
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