Amplitude Modulation

As you can guess, quadrature amplitude modulation is based on amplitude modulation.

The graph above is of some random signal, with an amplitude, or strength, of 1. This signal has a period of p (a period is the amount of time before a wave repeats itself). We might let a signal with amplitude 1 represent a binary 0.

This is the same sound wave as above, because it has the same period p. However, this signal has a higher amplitude of 2. We might let a signal with amplitude 2 represent a binary 1.

This is what amplitude modulation looks like. Notice that the period is the same for the entire signal, and that only the amplitude varies.

Assuming amplitude 1 = binary 0, and amplitude 2 = binary 1, this signal would represent 0011010.