Which statement best describes spread-spectrum communication?

• A. It varies the RF carrier according to a predetermined sequence
• B. It uses a single narrowband carrier with simple modulation
• C. It relies on high-power amplifiers
• D. It minimizes bandwidth usage

Answer: (A)

Spread-spectrum communication spreads a signal across a wider portion of the spectrum by varying the RF carrier according to a predetermined sequence. This variation can happen in two common ways: direct-sequence spreading, where the data are multiplied by a high-rate pseudorandom code, and frequency-hopping spreading, where the carrier hops among frequencies following a hopping pattern. The key idea is that the carrier is not fixed; it changes according to a code, which broadens the overall bandwidth of the transmitted signal. This broadening improves resistance to interference and jamming and allows multiple users to share the same spectrum more effectively.

The option describing a single narrowband carrier with simple modulation does not reflect spread-spectrum behavior, since spread-spectrum intentionally uses a wide bandwidth rather than a narrow one. The notion of relying on high-power amplifiers isn’t what defines spread-spectrum, and the idea of minimizing bandwidth usage contradicts the purpose of spreading the signal over a larger band.