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.