sideband
In electronic signal transmission, a sideband is the portion of a modulated carrier wave that is either above or below the basic ( Baseband ) signal. The portion above the baseband signal is the upper sideband ; the portion below is the lower sideband . In regular amplitude modulation ( AM ) transmission, both sidebands are used to carry a message. In some forms of tranmission, one sideband is removed ( single-sideband transmission ) or a portion of one sideband is removed.