Modulation ASK, FSK & PSK Constellation MATLAB Simulink MATLAB Code Comparisons among ASK, PSK, and FSK Comparisons among ASK, PSK, and FSK ASK or OFF ON Keying Ask is a simple (less complex) Digital Modulation Scheme where we vary the modulation signal's amplitude or voltage by the message signal's amplitude or voltage. We select two levels (two different voltage levels) for transmitting modulated message signals for the exam. And for example, we mapped the signal as two-level "+5 Volt" (which is the upper level) and another level, "0 Volt," which is considered as the lower level. Whenever we need to transmit binary bit "1," then the transmitter transmits a signal of "+5 Volts," and when we need to send bit "0," then it transmits no power. But the receiver is intelligent enough to deflect whether you've sent binary bit "1" or "0