信号的幅度调制原理

调制是将要传送的信息装载到某一高频(载波)信号上去的过程。幅度调制是用调制信号去控制载波的振幅,使其随调制信号线性变化,而保持载波的频率不变。在幅度调制中,根据已调信号的频谱分量不同,分为普通调幅(标准调幅AM)、抑制载波的双边带调幅(DSB)、抑制载波的单边带调幅(SSB)等。它们的主要区别是产生的方法和频谱结构不同。普通调幅(AM)的载波不含信息却占用了大部的信号能量,从而造成白白的浪费,抑制载波调幅(DSB、SSB)只发送边带信号,效率明显提高,但是在解调时需要恢复被抑制的载波。

Modulation Principle of the Range of Signal

Modulation is the process of loading the information to be delivered onto a certain(signal carrier) signal of high frequency. Amplitude modulation is to control the amplitude of signal carrier and make it change linearly with modulation signals and maintain its frequency.In the modulation of amplitude,there are ordinary amplitude modulation(the standard amplitude modulation AM),restraint signal carrier Double Side Band(DSB) and restraint carrier Single Side Band(SSB) according to the numbers of frequency spectra of the selected modulated signals.Their major differences are the formation methods and the structures of frequency spectra.The signal carrier power of ordinary amplitude modulation(AM) does not contain information,but occupies larger part of the signal energy,therefore cause a great waste of energy.Restraint carrier amplitude modulations(DSB and SSB) dispatch side band signal only,obviously with high efficiency,however in demodulation,the restricted signal carriers need to be restored.