![]() Some PSK systems are designed so that the carrier can assume only two different phase angles, each change of phase carries one bit of information, that is, the bit rate equals the modulation rate. For example, when encoding bits, the phase shift could be 0 degree for encoding a "0," and 180 degrees for encoding a "1," or the phase shift could be –90 degrees for "0" and +90 degrees for a "1," thus making the representations for "0" and "1" a total of 180 degrees apart. PSK in a digital transmission refers to a type of angle modulation in which the phase of the carrier is discretely varied-either in relation to a reference phase or to the phase of the immediately preceding signal element-to represent data being transmitted. ![]() FSK modulation formats generate modulated waveforms that are strictly real values, and thus tend not to share common features with quadrature modulation schemes. ![]() In coherent forms of FSK, there is no phase discontinuity in the output signal. In noncoherent forms of FSK, the instantaneous frequency shifts between two discrete values termed the "mark" and "space" frequencies. FSK is divided into noncoherent and coherent forms. The carrier signal is then modulated among the members of a set of discrete values to transmit information.įSK refers to a type of frequency modulation that assigns bit values to discrete frequency levels. ![]() Amplitude-shift keying (ASK), frequency-shift keying (FSK), and phase-shift keying (PSK) are digital modulation schemes.ĪSK refers to a type of amplitude modulation that assigns bit values to discrete amplitude levels. ![]()
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