Question

In binary data transmission, DPSK is preferred over PSK because

• A. more protection is provided against impulse noise
• B. for a given energy per bit, the probability of error is less
• C. the 180° phase shifts of the carrier are unimportant
• D. a coherent carrier is not required to be generated at the receiver

Hint:

The "D" in DPSK stands for Differential. This means information is in the difference between symbols. This makes the receiver "non-coherent" because it doesn't need an external coherent reference carrier, simplifying its design.

Answer 1

The Correct Option is D

Step 1: PSK Explained.Coherent PSK requires the receiver to create a local carrier wave perfectly synchronized in phase with the received carrier. This synchronized wave acts as a reference for determining the received signal's phase. However, generating this coherent carrier adds complexity and cost to the receiver.
Step 2: DPSK Explained.DPSK encodes information in the phase difference between successive symbols, rather than the absolute phase. For instance, a '1' could be indicated by no phase change, while a '0' is represented by a 180° phase shift. The receiver demodulates the signal by comparing the phase of the current symbol to that of the preceding symbol.
Step 3: PSK vs. DPSK.DPSK utilizes the prior symbol as its phase reference, eliminating the need for a separate, locally generated coherent carrier. This significantly simplifies the receiver's design. Although DPSK exhibits a slightly higher bit error rate compared to ideal coherent PSK at the same SNR, its key benefit lies in avoiding complex carrier recovery circuits.