Types of Conversions Cont

™   Phase Shift Keying (PSK) o    In PSK, phase of carrier is varied to represent binary 1 or 0 o    Both peak amplitude and frequency remains constant as the phase changes o    For Example: if we start with a phase of 0 degrees to represent binary 0 , then we can change the phase to 180 degrees to send binary 1 o    The phase of signal during duration is constant and its value depends upon the bit (0 or    2PSK    The above method is often called 2 PSK, or Binary PSK, because two different phases ( 0 and 180 degrees) are used    Figure  makes  this  point  clear  by  showing  the  relationship  of  phase  to bit value    A second diagram called constellation diagram or phase state diagram shows same relationship by illustrating only the phases ƒ     Effect of Noise on PSK o    PSK  is  not  susceptible  to  the  noise  degradation  that  affects  ASK,  nor  to  the bandwidth limitations of FSK o    Smaller variations in signal can be detected reliably by the receiver    4PSK