ELEC202 W1

发表于 2022-02-04 更新于 2022-04-07 分类于 ELEC202 阅读次数： Valine：

承上启下，信号调制。

ELEC202 WEEK1

ELEC202 COMMUNICATION SYSTEMS 顾名思义，就是信号在系统之间传输。因此，不仅仅是上学期那样的信号分析，更有各种基于应用的概念/理论/操作亟待学习。

Source encoder/input transducer (编码源) converts message into message signal.

Transmitter (发射器) converts message signal or bits into format appropriate for channel transmission (analog/digital signal).

Channel (信道) introduces distortion, noise, and interference.

Receiver (接收器) decodes received signal back to message signal.

Source decoder (解码器) decodes message signal back into original message.

一些概念：

•Information source device producing information to be communicated

•Binary digit (bit) fundamental information unit for all digital systems; unit of information content

•Bit stream sequence of binary digits, baseband

•Digital symbol group of bits considered as a unit or character

•Digital waveform analogue signal representing a digital symbol

信号与噪声功率之比 \[ SNR=\frac{P_{signal}}{P_{noise}}=\frac{\overline{A_{signal}}^2}{\overline{A_{noise}}^2} \]

Baseband 基带 describesthe band of frequencies representing the original signal as delivered by the input transducer.

Eg. the voice signal from a microphone is a baseband signal, and contains frequencies in the range of 0-3000 Hz

Bandpass describesthe band of frequencies significantly higher than that of the original signal, i.e. after modulation, usually wireless.