JPL's Wireless Communication Reference Website

Chapter: Analog and Digital Transmission
Section: Analog Modulation

Amplitude modulation


Figure: Phasor Diagram for AM with tonal modulation.

In the animation below, we demonstrate the phasor motion for AM with tonal modulation. The three blue phasor represent

The modulation index is 1. The sidebands are so large that, added to the carrier, they sometimes exactly give zero amplitude.

Note that the quadrature phase component of the resulting signal (in black) is always zero, and that the inphase component is always non-negative.


JavaTM Applet: Phasor diagram of a carrier with AM tone modulation.



JPL's Wireless Communication Reference Website 1993, 1996.