Which modulation technique is used to avoid phase ambiguity in BPSK?

Explanation:

Correct Option: Differential Phase Shift Keying (DPSK)

Definition: Differential Phase Shift Keying (DPSK) is a modulation technique used in digital communication systems. It is a variant of Phase Shift Keying (PSK) where the phase of the carrier signal is shifted relative to the previous signal element rather than a fixed reference signal. This technique helps in avoiding phase ambiguity issues that are common in Binary Phase Shift Keying (BPSK).

Important Information:

Analysis of Other Options:

QPSK (Quadrature Phase Shift Keying): QPSK is a modulation technique that uses four distinct phase shifts (0, 90, 180, and 270 degrees) to encode two bits per symbol. Although QPSK increases the data rate and spectral efficiency compared to BPSK, it does not inherently address the phase ambiguity issue. QPSK requires a coherent reference signal for demodulation, which can be challenging to maintain in environments with high phase noise.

ASK (Amplitude Shift Keying): ASK is a modulation technique where the amplitude of the carrier signal is varied to represent binary data. While ASK is simple and easy to implement, it is highly susceptible to noise and amplitude variations, making it less robust compared to phase-based modulation schemes. ASK does not address phase ambiguity issues and is not commonly used in scenarios where phase coherence is critical.

FSK (Frequency Shift Keying): FSK is a modulation technique where the frequency of the carrier signal is varied to represent binary data. While FSK is robust to amplitude noise and provides good performance in noisy environments, it does not address phase ambiguity issues. FSK is typically used in applications where frequency stability is more critical than phase coherence, such as in low-speed data communication and radio transmissions.