General exam question G7C09
Subelement G7, PRACTICAL CIRCUITS· Group G7C
What is the phase difference between the I and Q RF signals that software-defined radio (SDR) equipment uses for modulation and demodulation?
- A.Zero
- B.90 degrees (correct answer)
- C.180 degrees
- D.45 degrees
WhyThe I and Q RF signals that software-defined radio equipment uses for modulation and demodulation have a phase difference of 90 degrees. SDR hardware and software generate and process the I (in-phase) and Q (quadrature) signal components with a fixed 90-degree phase offset between them, which is what lets the math recover both amplitude and phase information needed for arbitrary modulation and demodulation, answer B. A phase difference of zero, 180, or 45 degrees wouldn't give the two components the independent information content that true quadrature (90-degree) signals provide.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2023-2027 NCVEC Element 3 pool (public domain); the explanation above is original writing, see our methodology.
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