Phase Shift Keying | PSK

Computer data is binary in nature and consists of sequence of 1s and 0s. Telephone lines are analog in nature and can carry only analog electrical signals. So devices called MODEMs are needed to transmit data over telephone lines.

PSK (Phase Shift Keying)

PSK is also known as 2-level PSK, because number of phase changes = 2. Other name is: BPSK (Binary Phase Shift Keying)

PSK modulation waveforms are shown below:

PSK rule:

• Bit 1 is represented by carrier signal with phase ( ₁)
• Bit 0 is represented by carrier signal with phase ( ₂)

PSK features are as follows:

• Number of phase changes = Number of phases used = 2
• Constant variables: Amplitude and Frequency of the carrier
• Changing variable: Phase of carrier
• Number of bits transmitted at a time = 1

NOTE: If the incoming bit from computer is 1, then carrier with phase (say ₁) is transmitted. If the incoming bit from computer is 0, then carrier signal with phase (say ₂) is transmitted.

NOTE: In PSK, modulating voltage (i.e., input voltage) is used to vary phase of the carrier (Refer my video lecture on Modulation in Electronic Communication System)