What are phase shift keying (PSK), frequency shift keying (FSK), and amplitude shift keying (ASK)?
PSK, FSK, and ASK are modulation schemes that allow the transmission of information over an electrical signal. Modulation is the process of varying one or more properties of a high frequency periodic waveform respect to a signal carrying actual information. The three key parameters of a periodic waveform are its amplitude, its phase and its frequency. When coupled with demodulation, this technique can be used to transmit a signal through a channel, such as air (radio frequencies) or a fiber optic cable (light frequencies). Different modulation schemes allow greater bandwidth, as multiple bits of information can be sent as "symbols".
Phase shift keying is relatively simple and inexpensive to implement. Examples of applications using Phase shift keying include wireless lan and bluetooth. Frequency shift keying in its simplest configuration is a binary implementation. Early telephone modems used FSK. Amplitude shift keying represents data as variations in the amplitude of the carrier signal. It is sensitive to distortions in the atmosphere, but has been used more practically in fiber optic applications. Typical implementation is binary, with the changes in amplitude being of the on/off variety.