通信工程专业英语考试总结

一单元：

By a communication system we will mean a system of the type indicated schematically in Figure 1.1.It is

consists of essentially five parts: 我们用示意图图1.1表明类型的系统说明通信系统。它包含了5重要的部分： 1.An information source which produces a message or sequence of messages to be communicated to the

receiving terminal. The message may be of various types:

1.一个信息来源，产生一个被送至接收端的消息或消息序列。这个消息可能有各种类型。

(a) A sequence of letters as in a telegraph of teletype system;(b) A single function of time f(t) as in radio or telephony;

（a） 在一个电报系统的电报的一个字母序列如；（b）在收音机或电话中的一个单一时间函数f（t）；

(c) A function of time and other variables as in black and white television—here the message may be thought of as

a function f(x,y,t) of two space coordinates and time, the light intensity at point(x,y) and time t on a pickup tube

plate; （c）一个时间函数和在黑白电视机的其他变量——这里信息可能被认为一个两个空间坐标和时间的函

数f（x，y，t），在点（x，y）的光强度和在一个摄像管的板子上的时间t； (d) Two or more functions of time, say f(t),g(t),h(t)—this is the case in three dimensional sound transmission or if

the system is intended to service several individual channels in multiplex;

（d）两个或更多的时间函数，像f（t）、g（t）、h（t）——这是三维音频传输的形式或如果系统想维护多路复用系统中的几条单独信道；

(e) Several functions of several variables—in color television the message consists of three functions f(x,y,t),

g(x,y,t) and h(x,y,t) defined in a three-dimensional continuum--

（e）几个多变量的函数——在彩色电视机中，信息包含在一个三位连续统中定义的三个函数f（x，y，t）、

g（x，y，t）和h（x，y，t） --we may also think of these three functions as components of a vector field defined in the region—similarly,

several black and white television sources would produce messages consisting of a number of functions of three

variables;

我们或许还认为这三个函数作为一个域内定义的矢量场的成分——相似的，几台黑白电视机信息来源将产生包含许多三变量的函数的信息； (f) Various combinations also occur, for example, in television with an associated audio channel.

（f）许多组合同样出现，例如，电视中有关联的音频信道。

2. A transmitter which operates on the message in some way to produce a signal suitable for transmission

over the channel. In telephony this operation consists merely of changing sound pressure into a proportional

electrical current. 2.一个发送器将消息用些方法处理产生适用在信道中传输的信号。在电话中这个操作仅仅包含改变声压为一个成比例的电流。

In telegraphy we have an encoding operation which produces a sequence of dots, dashes and spaces on the channel

corresponding to the message. 在电报中我们有一个编码操作产生相符于信息的一些连续的点、破折号和空格在信道中。

In a multiplex PCM system the different speech functions must be sampled, compressed, quantized and encoded,

and finally interleaved properly to construct the signal.

在一个多路复用PCM系统中不同的语音函数必须被抽样、压缩、量化和编码，且最终被适当地交叉存取来构造信号。

Vocoder systems, television and frequency modulation are other examples of complex operations applied to the message to obtain the signal.

语音编码器系统、电视和频率调制器是其他复杂操作用于信息来获得信号的例子。

3.The channel is merely the medium used to transmit the signal from transmitter to receiver. It may be a pair

of wires, a coaxial cable, a band of radio frequencies, and a beam of light, ect. 3.信道仅仅是从发送器传送信号到接收器的媒介。它或许是一双金属丝，一条同轴缆，一波段的收音机频率和一束光，等等。

4.The receiver ordinarily performs the inverse operation of that done by the transmitter, reconstructing the

message from the signal.

5.The destination is the person (or thing) for whom the message is intended. 4.接收器通常完成反向操作发送器做的事，重构来自信号的信息。

5.目的地是信息计划的人（或物）

We wish to consider certain general problems involving communication systems. To de this it is first

necessary to represent the various elements involved as mathematical entities, suitably idealized from their

physical counterparts. 我们希望考虑确凿的普遍的涉及通信系统的问题。做这些首先需要提出许多相关的因素作为数字实体，

适当地从它们的物理对应物借鉴。

We may roughly classify communication systems into three main categories: discrete, continuous and mixed.

By a discrete system we will mean one in which both the message and the signal are a sequence of discrete

symbols. 我们可以大概的将通信系统分成主要三类：离散的、连续的和混合的。离散系统对于我们就意味着信

息和信号是一系列的离散符号。

A typical case is telegraphy where the message is a sequence of letters and the signal is a sequence of dots,

dashes and spaces. 电报是一个典型的例子，系统中信息是一系列的字母且信号时一系列的原点、破折号及空格。 A continuous system is one in which the message and the signal are both treated as continuous functions, e.g.,

redio or television. A mixed system is one in which both discrete and continuous variables appear, e.g., PCM

transmission of speech. 一个连续系统中信息和信号都能处理为连续的函数，如，收音机或电视。一个混合的系统中离散、连

续变量均会出现，如，PCM语音传输。 三单元：

Multiple access is a technique with which multiple terminals share the bandwidth of the transmission

medium. Multiple access techniques are of paramount importance in radio systems where the channel bandwidth is

very limited. In multiple access, multiple terminals or users share the bandwidth of the transmission medium. 译文：多址接入技术是多个通信终端共享通信媒介频段的技术。多址技术对于频段非常有限的无线通信系统而言是极其重要的。在多址接入技术中，多个通信终端或多个用户共享传输媒介频段