Generation of ASK modulated signals

We have already seen that an ASK signal can be realized using a mixer to multiply the carrier with the baseband symbol stream. This is termed a linear modulation process.
A simpler alternative, particularly for binary ASK, is to use a switch to gate the carrier on and off, driven by the data signal. For more than two symbol states, this approach becomes quite complicated with the requirement to gate on carriers with differing amplitudes to represent the required number of symbol states.