 The terms "I-component" and "Q-component" are common ways of referring to the in-phase and quadrature signals.Both signals comprise a high-frequency sinusoid (or "carrier") that is amplitude-modulated by a relatively low-frequency function, usually conveying some sort of information.The two carriers are orthogonal, with I lagging Q by ¼ cycle, or equivalently leading Q by ¾ cycle.