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ASK - amplitude shift keying
Amplitude shift keying is a signal transform method when the carrying oscillation amplitude changes abruptly depending on the discrete data messages.
At amplitude shift keying each digital symbol has its own carrier signal amplitude matching it. Manipulated signal frequency and phase stay the same. Amplitude shift keying is used very seldom in practice due to its noise resistance rather low comparing to the other shift keying types. Amplitude shift keying is often used together with the other shift keying types.
The picture below shows the graphical chart of zeros and unities binary order as well as the relevant amplitude shift keyed signal chart. To code the binary signal low level - 0.5 Vpp is used, to code the high level – sinusoidal carrier signal 1 Vpp.
The next picture shows the example of the amplitude shift keying of sinusoidal carrier signal, double-digit code is an information signal.
The following picture demonstrates two-point amplitude shift keying where carrier signal amplitude (yellow ray) takes on two different values depending on the rectangular signal level (blue ray) controlling the shift keying.