This Demonstration illustrates the effect of changing the modulation factor (also called the modulation depth) on the power efficiency of ordinary amplitude modulation (AM) technique. A modulation factor greater than 1 results in envelope distortion, causing difficulties during demodulation. Hence must be kept less than 1.
At 100% modulation (, the power efficiency of AM is 33.33%, that is, the total power carried by the sidebands is 1/3 of the total power. The middle graph shows the modulated carrier , where is the message signal and is the modulation factor. For simplicity, the amplitude of the carrier signal and the amplitude of the message signal are both kept equal to 1.