What is QAM?

08/01/2024


What is QAM?


QAM Definitio


QAM (Quadrature Amplitude Modulation) is defined as a modulation technique that combines phase and amplitude modulation to transmit information.


 

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Working Principle


QAM changes both the amplitude and phase of a carrier wave to double the effective bandwidth.



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Analog vs Digital QAM



Analog QAM is used in traditional TV systems, while Digital QAM, known as Quantized QAM, is used in modern digital communications like Wi-Fi and cellular networks.


 

QAM Formats


Different QAM formats, such as 16-QAM, 32-QAM, and 64-QAM, vary in the number of bits they can transmit per symbol, represented in constellation diagrams.


 

 

Advantages of QAM


  • Noise immunity of QAM’s is very high hence noise interference is very less.



  • QAM has a low probability of error value.



  • QAM supports a high data rate. So that the number of bits can be carried by the carrier signal. Hence, it is mostly used in wireless communication systems.



  • QAM has a doubling the effective bandwidth.



  • By using both sine wave and cosine wave into single-channel the communication channel capacity is doubled compared to the use of only one sine wave or one cosine wave.



 

Disadvantages of QAM


  • In QAM, amplitude changes are susceptible to noise.



  • It is possible to transmit more bits per symbol but in higher-order QAM formats the constellation points are closely spaced which is more susceptible to noise and produces errors in the data.


 

Applications of QAM


  • QAM technique is widely used in the radio communications field because of the increase of the bit data rate.



  • QAM is used in applications ranging from short-range wireless communications to long-distance telephone systems.



  • QAM is used in microwave and telecommunication systems to transmit the information.


  • The 64 QAM and 256 QAM are used in digital cable television and cable modem.


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