模拟信号调制技术(FM/AM/PM/SSB)
来自Jack's Lab
目录 |
1 概述
信号相加的:
http://www.rfcafe.com/references/electrical/NEETS-Modules/NEETS-Module-12-2-1-2-10.htm
2 FM
* 信号:xm(t) = β·sin (Ωmt) * 载波:xc(t) = Xc·cos (Ωct) FM 调制后的波形为:x(t) = Xc·cos [Ωct + β·sin (Ωmt)]
Xc = 1, β= 25, Ωc = 2·PI·150, Ωm = 2·PI·10 的波形为:
Xc = 1, β= 5, Ωc = 2·PI·150, Ωm = 2·PI·10 的波形为:
http://www.rfcafe.com/references/electrical/frequency-modulation.htm
3 AM
* 信号:xm(t) = Xm·sin (ωmt) * 载波:xc(t) = Xc·sin (Ωct) AM 调制后的波形为:x(t) = Xc·[1 + m·sin (Ωmt)]·sin (Ωct)
Xc = 1, m = 1, Ωc = 2·PI·150, Ωm = 2·PI·10 的波形为:
正常的 sin (Ωmt)·sin (Ωct)
Ωc = 2·PI·150, Ωm = 2·PI·10 的波形为:
http://www.rfcafe.com/references/electrical/amplitude-modulation.htm
4 QAM
一种特殊的 AM 调制方式
基带两路信号:自己 BI 和移相 90 度后的自己 BQ
载波也两路:自己 CI 和移相 90 度后的自己 CQ
调制后的波形为:BI * CI + BQ * CQ
参考: I/Q信号
http://en.wikipedia.org/wiki/Quadrature_amplitude_modulation
5 PM
模拟通信未见有实际使用,数字调制有应用:http://en.wikipedia.org/wiki/Phase_modulation
6 SSB
单边带调制,业余无线电里的短波通信用的比较多
http://en.wikipedia.org/wiki/Single-sideband_modulation