The wave that is intended to be modulated in modulation, or, in a modulated wave, the carrier-frequency spectral component. The process of modulation produces spectral components falling into frequency bands at either the upper or lower side of the carrier frequency. These are sidebands, denoted upper or lower sideband according to whether the frequency range is above or below the carrier frequency. A sideband in which some of the spectral components are greatly attenuated is a vestigial sideband. In general these components correspond to the highest frequency in the modulating signals. A single frequency in a sideband is a side frequency. The baseband is the frequency band occupied by all the transmitted modulating signals.