FREQUENCY DIVISION DIVISION MULTIPLEXI MULTIPLEXING NG | FDM| Tutorial-... Tutorial-...
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FREQUENC FREQUENCY-DIVI Y-DIVI SION MULTIP LE LEXI XI NG (FDM) ultiplexing Characteristics of Frequency Division M ultiplexing There are some multiplexing concept, here we will explain the Frequency Division Multiplexing .FDM-Frequency .FDM-Frequency Division Division Multiplexing Multiplexing is possibl possible e when the useful useful bandwidth of the transmission medium exceeds the required bandwidth of signals to be transmitted. transmitted. A number of signals signals can be carried simultaneous simultaneously ly if each signal is modula modulated ted onto onto a differe different nt carrier carrier frequen frequency cy and the the carrier carrier frequen frequencie cies s are sufficien sufficiently tly separated that the bandwidth bandwidths s of the signals signals do not overlap.
Figure Figure
below describe a FDM-Frequency Division Multiplexing:
Frequency-division multiplexing others definition of Frequency-division Frequency-division multiplexing multiplexing (FD M ) is a scheme in which numerous signals are combined for transmission on a single communications line or channel. Each signal is assigned a different frequency (subchannel) within the main channel of the tra nsmission. Frequency Division multiplexing or FDM is an analog technique which is used to multiplex signals. Frequency Division multiplexing or FDM can be applied when the bandwidth of a link (in her tz) is greater than the combined bandwidths of the signals to be transmitted. In FDM, the signals generated by each sending device modulate different carrier frequencies. After that, these modulated signals are combined into a single composite signal that can be transported by the link. Carrier frequencies are separated separated by sufficie sufficient nt band width to acco accommodate mmodate the modulated modulated signal. These These bandwidth ranges are the channels through which the various signals travel. From
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signal signal sources sources are fed into a multiplexer , which which modulates modulates each signal signal onto onto a different frequency (fi, . . . , f6). Each modulated signal requires a certain bandwidth cent centere ered d aroun around d its its carri carrier er freq freque uenc ncy, y, referr referred ed to as a chan channe nel. l. To preve prevent nt interference, the channels are separated by guard bands, which are unused portions of the spectrum. The composite signal transmitted across the medium is analog. Note, however, that the input input signal signals s may be either either digital digital or analog analog.. In the case of digital digital input input,, the input signals must be passed through modems to be converted to analog. In either case, each input analog signal must then be modulated to move it to the appropriate frequency band. When F DM is used in a communicat communications ions network, each input signal is sent and received at maximum speed at all times. This is its chief asset. However, if many signals signals must be sent along a single single long-dis long-distanc tance e line, the necessary necessary bandwidth bandwidth is large, and careful engineering is required to ensure that the system will perform prop proper erly ly..
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FREQUENCY DIVISION MULTIPLEXING | FDM| Tutorial-...
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Disadvantages FDM - Frequency Division Multiplexing is not sensitive to the propagation / development delays. Technics equation channel (channel equalization) needed for FDM systems are not as complex as used in the TD M Time-Division Multiplexing system. Advantages In Frequency division multiplexing there is a need to filter bandpass, the price is relatively expensive and complex to be built (the use of these filters are usually used in the transmitter and receiver). In Frequency division multiplexing Power amplifier (power amplifier) in the transmitter that is used has the characteristics of the nonlinear (linear amplifier is more complex to be made), and nonlinear amplification lead to the making of the spectral components out-of-band that can interfere with other FDM channels.
