Question
What is vestigial sideband modulation?
Answer Options
- A) Amplitude modulation in which one complete sideband and a portion of the other are transmitted
- B) A type of modulation in which one sideband is inverted
- C) Narrow-band FM modulation achieved by filtering one sideband from the audio before frequency modulating the carrier
- D) Spread spectrum modulation achieved by applying FM modulation following single sideband amplitude modulation
Correct Answer: A
Explanation
Vestigial Sideband (VSB) is a method of amplitude modulation that is an effective compromise between bandwidth efficiency and signal complexity. It is primarily used in standard television broadcasting (NTSC and ATSC) and is often adopted for amateur Fast-Scan TV (ATV) transmissions to fit the signal into designated channels.
VSB modulation is amplitude modulation in which one complete sideband and a portion of the other are transmitted. This technique achieves a significant reduction in required channel bandwidth compared to full Double Sideband (DSB) AM, but it avoids the complexity of generating a pure Single Sideband (SSB) signal. The small transmitted portion of the second sideband (the ‘vestige’) ensures good low-frequency response.
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