通信原理(英文版)总复习.
通信原理(英文版)
2.1 Classification of Signals
2.1.1 Deterministic signals and random signals
• What is deterministic signal? • What is random signal?
2.1.2 Energy signals and power signals
f (t) f (t T) t
Its frequency spectrum is
/2
C( jn0 )
1 T
/ 2 Ve j n0t dt
/ 2
1 T
V
jn 0
e
j n0 t
/ 2
V e j n0 / 2 e j n0 / 2
f (t) sin(t) Its frequency spefct(rtu)m: f (t 1)
0 t 1 t
C(
jn 0 )
1 T0
T0 / 2 s(t )e jn0t dt
T0 / 2
1 sin(t )e j 2nt dt
Solution: Let the expression of the rectangular pulse be
Then its frequency spectral density is
its
Fourier
tragns(fto)rm:
1
0
t /2 t /2
G() / 2 e jt dt 1 (e j / 2 e j / 2 ) sin( / 2)
通信原理课后总结复习题
1.1已知英文字母e 出现的概率为0.105。
x 出现的概率为0.002，试求e 和x 的信息量。
解：25.3105.0log )(log )(22=-=-=E P E I （bit ）97.8002.0log )(log )(22=-=-=x P x I （bit ）1.3设有四个符号，其中前三个符号的出现概率分别为1/4, 1/8,1/8,且各符号的出现是相互独立的。
试计算该符号集的平均信息量。
解：)(log )()(241i i i x P x P X H ∑=-=75.121log 2181log 8181log 8141log 412222=----=（bit/符号）1.4，一个由字母A.B.C.D 组成的字，对于传输的每一个字母用二进制脉冲编码，00，01,10,11分别代替A.B.C.D ，每个脉冲宽度为5ms ，（1），不同的字母是等可能出现时，使计算传输的平均信息速率。
（2），若四个字母出现的概率分别为1/5,1/4,1/4,3/10，试计算传输的平均信息速率。
解：（1）因一个字母对应两个二进制脉冲，属于四进制符号，故一个字母的持续时间为2*5ms ， 传送字母的符号速率为等概率时，平均信息速率为（2）每个符号的平均信息量为：H==1.985bit/符号。
平均信息速率为： 1.10已知某四进制数字传输系统的传信率为2400b/s ，接收端在0.5h 内共收到216个错误码元，试计算该系统的误码率Pe 。
4.5，某个信息源有A.B.C 和D 等四个符号组成，设每个符号独立出现，其出现概率分别为1/4,1/4,3/16, 5/16，经过信道传输后，每个符号正确接受的概率为1021/1024，错为其他符号的条件概率P()均为1/1024，试画出此信道模型，并求出该信道的容量C 等于多少b/符号。
解：信道模型如图所示：粗线表示概率1021/1024，细线表示概率1/1024. H(x)=H(x|y)=C = H(x)- H(x|y)=1.967 bit/符号。
通信专业英语复习要点
通信专业英语复习要点一、翻译下列短语：1.汉译英：公众电信网 public telecommunication network 数据流量 data traffic音频电路交换接点电话用户 telephone subscriber 全球通信 global communications传输媒体 transmission medium 接口设备开放网络Open network语音编码 voice encoding光源 light source 宽带用户 wideband subscriber单模光纤波分复用通信卫星 communication satellite 信息安全 information security定时信号地下电缆数据终端 data terminals电子邮件 electric mail 远程终端 remote terminal网络资源 network resource 用户界面无线信道点播业务on-demand services数字信号视频压缩全活动图像 motion picture 存储电话交换台寻呼业务单向通信移动电话网 mobile telephone network 无线发射机模拟方式短消息服务 short message service 国际漫游 international roaming通信标准 communication standards 基站2. 英译汉：national networks 国家网络local loop本地环路full-duplex connection 全双工的连接transmission facilities传输设备high-usage trunks 高效中继线pulse code modulation 脉码调制digital communication 数字通信bandwidth limitations 带宽限制the integrated digital networkexperimental technologySome type of data conversion equipment 某些类型的数据转换设备？Coding process in the data transmitterTransmission impairmentsMagnetic core memories 磁心存储器Long distance transmission 长途传输Commercial technology 商用技术Optical fibre communicationMultifibre connectorsInformation capacity 信息容量Broadband service 广播业务Digital signal processorhigh definition television 高清晰电视Colour monitor 彩色显示器hard disk storage 硬盘存储Interactive environment 交互环境network facilities resourcesElectronic conferencesworld wide webSearching tool 搜索工具live conversation 实时对话means to communicatethe called personthe paging systems using wireless transmissionglobal coverageuser terminaltime division multiple accessmarket growth 市场的发展the cost and quality of the linksubscriber register 用户寄存器digital signal processor 数字信号处理器hard disk storage 硬盘存储二、将下列短文译成中文：The fixed telephone service is global and the interconnection varies from coaxial cable to optical fibre and satellite. The national standards are different, but with common interfaces and interface conversion, interconnection can take place. For mobile the problem is far more complex, with the need to roam creating a need for complex networks and systems.国家电话业务是全球性的，系统的相互连接采用同轴电缆、光纤甚至卫星，虽然全国标准不同，但却采用共同的接口装置，使得相互连接可以进行，对移动通信来说，问题更加复杂，这是由于需要漫游业务就要有更复杂网络系统。
通信原理(英文版)
【Example 2.4】Find the waveform and the frequency spectral density of a sample function. Solution: The definition of the sample function is
sin t Sa ( t ) t
d(t)
1
(f)
0
t
0
f
meaning of d function: It is a pulse with infinite height, infinitesimal width, and unit area. Sa(t) has the following property:
Physical
F ( ) lim
/2 / 2
cos 0 te
jt
sin[( 0 ) / 2] sin[( 0 ) / 2] dt lim 2 ( ) / 2 ( ) / 2 0 0
The frequency spectral density of d(t):
( f ) d (t )e
jt
d (t ) 0
t 0
dt 1 d (t )dt 1
7
d(t)
and its frequency spectral density:
f (t ) f (t 1) t
1
Its frequency spectrum:
1 C ( jn 0 ) T0
T0 / 2
T0 / 2
s(t )e
电子通信专业英语复习资料（自行归纳）
电子通信专业英语复习资料（自行归纳）一、英译汉P35 The reduction in power dissipation is particularly important where acomplex circuit is to be concentrated into a small space.The problem of extracting theheat generated in the circuit may then be a difficult one.减小功率损耗是非常重要的，其方法是将一个复杂的电子线路集成为一小块。
这使得释放电路工作时产生的热量变成一个难题。
P48 [4] A CD-ROM can store in excess of 500 megabytes (millions of bytes) of data-as compared with computer's hard disk,whose maximum storage capacity is about 200megbytes 和计算机硬盘相比，一个只读存储器可以存储超过500 MB的数据，它的最大存储容量大约为200 MB。
P64 [2] The original source information can be in analog (continuous) form,such as thehuman voice or music,or in digital (discrete) form,such as binary-coded numbers or alphanumeric codes.原始的信息源既可以是模拟(连续)的，例如语音或音乐; 也可以是数字(离散)的，例如二进制编码数或字符码。
P100 [4] As data networks advanced from terminal-oriented systems to packet-switched, Computer-to-computer linkups,the protocols necessary to make networks function alsogrew more complex.由于数据网络从面向终端的系统向分组交换、计算机与计算机连接的方向发展，执行网络功能所必需的协议也变得愈来愈复杂。
通信原理(英文版)
can be generalized to power signal.
10
Energy spectral density
Let the energy of an energy signal s(t) be E, then the energy
of
the
signal
is
decided
byE
s2 (t)dt
is
S() s(t)e jt dt
The inverse Fourier transform of S() is the original signal:
s(t) S ()e jtd
【Example 2.3】Find the frequency spectral density of a rectangular pulse.
0, 当t 0,
u(t)
1,
当t 0
1
u(t) = d(t)
0
Fig. 2.2.6 Unit step function
t
➢ Difference between frequency spectral density S(f) of
energy signal and frequency spectrum of periodic power
Chapter 2 Signals
2.1 Classification of Signals
2.1.1 Deterministic signals and random signals
➢ What is deterministic signal? ➢ What is random signal?
通信原理(英文版)1
大家好
2
1.2 Message, information & signal
Message：speech, letters, figures, images…
Information：effective content of message. Different types of messages may contain the same information
Demodulation
Channel
Modulation
Informitter
1.3.4 Specifications of Digital
Communication Systems
Relationship between efficiency & reliability (rate ~ accuracy)
Two categories of signals
• Analog signal：Its voltage or current can be expressed by a continuous function of time. For example, speech signal.
• Digital signal： Its voltage or current can only take finite number of discrete values. For example, digital computer data signal.
(MF)
direction-finding, distress
calling, coast guard
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17
Division of frequency band
通信原理(英文版)
I = log2 [1/P(x)] = log2 [1/(1/2)] = 1 bit
4
# For an equal probability M-ary symbol:
I = log2 [1/P(x)] = log2 [1/(1/M)] = log2 M bit If M = 2k ，then I = k bit
Out put S/N increases with bandwidth according to exponential law.
10
Digital communication system model 11
2
1.2 Message, information & signal
Message：speech, letters, figures, images…
Information：effective content of message. Different types of messages may contain the same information
5
1.3 Digital Communication
1.3.1 Basic concept
Two categories of signals • Analog signal：Its voltage or current
can be expressed by a continuous function of time. For example, speech signal.
# Ex: “Rainfall will be 1 mm tomorrow” – information content small