Quadrature Amplitude Modulation
Introduction
Quadrature Amplitude Modulation (QAM) is a method used for transmitting data in the form of two separate carriers, which are out of phase by 90 degrees, or in quadrature. This technique is commonly used in many digital data communication systems, including DSL technology and Wi-Fi.
Principle of Operation
QAM operates by varying the amplitude of two carrier waves, most often sinusoidal, that are out of phase with each other by 90 degrees. This is done in accordance with the input data signal. The two carrier waves are combined at the destination to create the final signal.
Types of QAM
There are several types of QAM, including 16-QAM, 64-QAM, and 256-QAM. The number in the name represents the number of distinct states or points in the constellation diagram. The higher the number, the more data can be transmitted, but the signal becomes more susceptible to noise.
Applications
QAM is used in many digital data communication systems. Some of the most common applications include television broadcasting, DSL internet service, and Wi-Fi technology.
Advantages and Disadvantages
QAM has several advantages, such as high data rate and spectral efficiency. However, it also has some disadvantages, including susceptibility to noise and the need for complex equipment.
See Also
