Amplitude Modulation (AM)
Amplitude modulation (AM) is a process that varies the amplitude of an RF carrier signal according to the amplitude of the message signal.
The recovery of the message signal is called demodulation. One of the benefits of amplitude modulation systems is the ease with which the baseband message signal can be recovered. Amplitude modulation generates discrete upper and lower sidebands, which are the sum and difference between frequencies of the message signal and the carrier signal.
The following figure illustrates the modulation of a carrier signal, figure a, by a message signal, figure b. The message signal shape is also referred to as the amplitude envelope. The result is the modulated wave, figure c.
Figure a shows a carrier signal with amplitude Ac. Figure b shows the baseband message signal. The transmitted signal in Figure c is given by the following equation:
where m(t) is the time-varying modulation.
Refer to the NI Developer Zone at ni.com/zone for more information about amplitude modulation.