? Digital transmission provides a powerful method for overcoming noisy environments. ? 数字传输对于克服噪声环境的影响提供了一个强有力的手段（method方法）
? Noise can be introduced into transmission path in many different ways; perhaps via a
nearby lightning strike, the sparking of a car ignition system, or the thermal low-level noise within the communication equipment itself. ? sparking of a car ignition system ? 汽车点火系统的打火 ? thermal low-level noise
? 低电平的热噪声
? .噪声可以以多种不同的方式进入传输信道,比如说因为附近的闪电、汽车点火系统
的打火或因通信设备本身低电平热噪声所致.
? It is the relationship of the true signal to the noise signal, known as the signal-to-noise
ratio which is of the most interest to the communication engineer. ? 正是这种被称为信噪比的即真实信号与噪声的关系引起了通信工程师的极大的兴
趣.
? Basically, if the signal is very large compared to the noise level, then a perfect message
can take place; however, this is not always the case. ? this is not always the case
? 实际情况并非如此．
? 从本质上讲,如果信号比噪声电平大得多,则信息的传输是完美的.但是,实际情况并
不总是这样.
? For example, the signal received from a satellite, located in far outer space , is very weak
and is at a level only slightly above that of the noise. ? 例如, 从位于遥远太空中的卫星接收的信号极其微弱,其电平仅比噪声稍高一点.
? Alternative examples may be found within terrestrial systems where, although the
message signal is strong, so is the noise power.
? 地面系统则是另一类例子,尽管信号很强,噪声也很强.
电子专业英语考点ud
