What is vestigial sideband modulation?

Vestigial Sideband (VSB) is a type of amplitude modulation primarily used in analog television broadcasting, such as the classic NTSC standard. In VSB, one complete sideband is transmitted along with only a small remnant, or 'vestige,' of the other sideband. This technique is a clever compromise between traditional double-sideband AM and single sideband (SSB). It reduces the overall RF bandwidth compared to full AM but retains the carrier and low-frequency components of the second sideband, making it much easier to demodulate with a simple television receiver circuit than a pure SSB signal. The distractors are incorrect because VSB is strictly a form of amplitude modulation, not FM or spread spectrum. It also does not involve inverting a sideband, but rather filtering most of it out.