【精品】04通信原理B答案.doc

【精品】04通信原理B答案.doc学院 系别 班次 学号 姓名
密 封 线 以 内 答 题 无 效
电子科技大学二00四至二00五学年第 -学期
«通信原理 >> 课程考试题（B卷）（120分钟）考试日期2004年12月25日
一
二
三
四
五
六
七
八
九
十
总分
评卷教师
Blank Filling:
A analog waveform can be converted to digital signal (for a PCM system) by three basic operations: sampling、 quantizing、 coding .
A law and u law companding is the two main nonuniform quantizing used in PCM system.
The input amplitude of a linear circuit is 5V .The output amplitude is 10V. Then the gain of the circuit is 6 dB.
BANDPASS SAMPLING THEOREM: If a (real) bandpass waveform has
a nonzero spectrum only over the frequency interval fi < I f I < f2, where the transmission bandwidth BTis taken to be the absolute bandwidth BT= f2 - fi, then the waveform may be reproduced from sample values if the sampling rate is .
All communications systems involve three main subsystems : transmitter、 channel、
receiver .
Multiple Choice:
If the bandwidth of an modulation signal m(t) is f0, the bandwidth of AM, DSB-SC and SSB signal are[A)respectively
2f0, 2f0,f0 (B) f0,2f0,f0 (C) 2f°, f°, 2f0 (D) 2f0, 2f0,2f0
In the following definition, the right is —£D)
A bandpass waveform has a spectral magnitude that is zero for the frequency in the vicinity of the origin and negligible elsewhere
A baseband waveform has a spectral magnitude that is zero for the frequency in some band concentrated about a fre