QAMModulation

Quadrature Amplitude Modulation, or QAM, is a modulation scheme that conveys data by changing the amplitude of two carrier waves, called the quadrature carriers, in an orthogonal relationship. These carriers are typically a sine wave and a cosine wave, offset by 90 degrees. By varying the amplitude of both the in-phase (cosine) and quadrature (sine) carriers simultaneously, QAM can encode multiple bits of data onto a single symbol.

The number of possible amplitude levels for each carrier determines the number of bits per symbol. For example, 4-QAM uses two bits per symbol, requiring two distinct amplitude levels for each carrier. 16-QAM uses four bits per symbol and requires four distinct amplitude levels for each carrier. Higher order QAM schemes, such as 64-QAM and 256-QAM, allow for even greater data rates by increasing the number of possible amplitude combinations, but they are also more susceptible to noise and interference.

QAM is widely used in digital communication systems, including Wi-Fi, cable modems, and digital television broadcasting. Its ability to achieve high spectral efficiency, meaning it can transmit more data within a given bandwidth, makes it a crucial technology for modern wireless and wired communication. The process involves mapping digital data bits to specific amplitude combinations, which are then used to modulate the carrier waves. The receiver then demodulates the signal by detecting these amplitude levels and converting them back into digital data.