QAM

In a QAM signal, there are two carriers, each having the same frequency but differing in phase by 90 degrees (one quarter of a cycle, from which the term quadrature arises). One signal is called the I signal, and the other is called the Q signal. Mathematically, one of the signals can be represented by a sine wave, and the other by a cosine wave. The two modulated carriers are combined at the source for transmission. At the destination, the carriers are separated, the data is extracted from each, and then the data is combined into the original modulating information.

Also see bandwidth, modulation, and wireless.

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More resources from around the web: - Altera provides a brief description of how QAM works. - Williamson Labs provides a block diagram of a QAM transmitter.

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