Which statement correctly describes QPSK compared to BPSK?

Which statement correctly describes QPSK compared to BPSK?

• A. QPSK uses two phase states.
• B. QPSK uses four phase states.
• C. QPSK uses eight phase states.
• D. QPSK uses constant envelope with no phase states.

Answer: (B)

QPSK encodes data by using four distinct phase angles spaced 90 degrees apart, so it carries two bits per symbol. This is why it has four phase states. BPSK, by contrast, uses only two opposite phase angles (0 and 180 degrees), carrying one bit per symbol. Both schemes keep the carrier envelope constant, but the key difference is the number of phase states used to represent data. So the statement that QPSK uses four phase states correctly describes how it compares to BPSK.

QPSK encodes data by using four distinct phase angles spaced 90 degrees apart, so it carries two bits per symbol. This is why it has four phase states. BPSK, by contrast, uses only two opposite phase angles (0 and 180 degrees), carrying one bit per symbol. Both schemes keep the carrier envelope constant, but the key difference is the number of phase states used to represent data. So the statement that QPSK uses four phase states correctly describes how it compares to BPSK.