DATA COMMUNICATION PRINCIPLES Phase Shift Keying PSK Phase

DATA COMMUNICATION PRINCIPLES : Phase Shift Keying (PSK)

Phase Shift Keying (PSK) In this type of digital modulation, the data information is imbedded in the phase of the carrier. The same carrier frequency is used for both types of bits (0 and 1) but the phase is inverted for one or the other. There a number of ways of representing baseband data/signal in PSK. In simple binary PSK (or BPSK), two carrier signals are defined with same frequency and same amplitude but opposite phases. In differential BPSK, instead of defining two carrier signals with opposite phases, phase inversion is used to modulate one of the two types of binary signals. Figure 3 -15 shows simple BPSK in which a positive baseband pulse is modulated into a cosine function and a negative baseband pulse is modulated in the negative of a cosine function. In BPSK, the baud rate and bit rate are equal. This is because the carrier phase (360° or ) is equally divided into two halves. In a multi-phase PSK (called M’ary PSK or simply MPSK), the carrier phase may be divided into M equal parts. For M equal divisions of the phase, each of the M resulting signals will have one of the M values of phases between 0° and 360°. In MPSK, each symbol can represent as many as Thus, the bit rate would be k times the baud rate,

REFERENCES • Ahmad A. - Data Communication Principles. For Fixed and Wireless Networks • Cornelius T. Leondes - Database and Data Communication Network Systems, Three-Volume Set_. . -Academic Press