What is vestigial sideband modulation?

  1. Amplitude modulation in which one complete sideband and a portion of the other are transmitted
  2. A type of modulation in which one sideband is inverted
  3. Narrow-band FM modulation achieved by filtering one sideband from the audio before frequency modulating the carrier
  4. Spread spectrum modulation achieved by applying FM modulation following single sideband amplitude modulation