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Encyclopedia > Frequency division multiplexing

Frequency-division multiplexing (FDM) is a form of signal multiplexing where multiple baseband signals are modulated on different frequency carrier waves and added together to create a composite signal.


FDM can also be used to combine multiple signals before final modulation onto a carrier wave. In this case the carrier signals are referred to as subcarriers: an example is stereo FM transmission, where a 38 KHz subcarrier is used to separate the left-right difference signal from the central left-right sum channel, prior to the frequency modulation of the composite signal.


Where frequency division multiplexing is used as to allow multiple users to share a physical communications channel, it is called frequency-division multiple access (FDMA).


FDMA is the traditional way of separating radio signals from different transmitters.


The analog of frequency division multiplexing in the optical domain is known as wavelength division multiplexing.


See also


  Results from FactBites:
 
Adaptive antenna arrays for orthogonal frequency division multiplexing systems with co-channel interference - Patent ... (5675 words)
Orthogonal frequency division multiplexing systems may be subject to co-channel interference in a cellular mobile communications environment in which frequency reuse considerations result in the same carrier frequency being used for different communications in adjacent or nearby cells.
In an orthogonal frequency division multiplexing system, the received signals are correlated for different blocks and tones and the temporal estimation of instantaneous correlation between signals received by the ith and jth antennas, r.sub.ij [n,k], is defined as x.sub.i [n,k].cndot.x.sub.j *[n,k].
The frequency domain correlation matrix S.sub.f =WAW.sup.H, where W is a discrete Fourier transform matrix defined as shown in equation 19 and A is a diagonal matrix with the elements shown in equation 20; ##EQU9## where.times.
Frequency-division multiplexing (142 words)
Frequency-division multiplexing (FDM) is a form of signal multiplexing where multiple baseband signals are modulated on different frequency carrier waves and added together to create a composite signal.
Where frequency division multiplexing is used as to allow multiple users to share a physical communications channel, it is called frequency division multiple access (FDMA).
The analog of frequency division multiplexing in the optical domain is known as wavelength division multiplexing.
  More results at FactBites »

 
 

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