Question
What is the phase difference between the I and Q RF signals that software-defined radio (SDR) equipment uses for modulation and demodulation?
Answer Options
- A) Zero
- B) 90 degrees
- C) 180 degrees
- D) 45 degrees
Correct Answer: B
Explanation
Software-Defined Radio (SDR) transceivers often rely on a quadrature detection and generation technique, utilizing In-phase (I) and Quadrature (Q) signals. The I signal is the reference signal, and the Q signal is derived by phase-shifting the reference.
For quadrature detection, the I and Q signals must be exactly 90^\circ out of phase with each other. This 90 \text{ degree} phase difference is essential for determining the phase and amplitude relationship of the received signal, allowing the SDR to generate or demodulate complex modes like Single Sideband (SSB), which relies heavily on phase manipulation.
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