frequency division multiplexing

(communications)(FDM) The simultaneous transmission ofmultiple separate signals through a shared medium (such as awire, optical fibre, or light beam) by modulating, at thetransmitter, the separate signals into separable frequencybands, and adding those results linearly either beforetransmission or within the medium. While thus combined, allthe signals may be amplified, conducted, translated infrequency and routed toward a destination as a single signal,resulting in economies which are the motivation formultiplexing. Apparatus at the receiver separates themultiplexed signals by means of frequency passing or rejectingfilters, and demodulates the results individually, each in themanner appropriate for the modulation scheme used for thatband or group.

Bands are joined to form groups, and groups may then be joinedinto larger groups; this process may be consideredrecursively, but such technique is common only in large andsophisticated systems and is not a necessary part of FDM.

Neither the transmitters nor the receivers need be close toeach other; ordinary radio, television, and cable service areexamples of FDM. It was once the mainstay of the longdistance telephone system. The more recently developed time division multiplexing in its several forms lends itself tothe handling of digital data, but the low cost and highquality of available FDM equipment, especially that intendedfor television signals, make it a reasonable choice for manypurposes.

Compare wavelength division multiplexing, time division multiplexing, code division multiplexing.

单词	frequency division multiplexing
释义	DictionarySeefdm frequency division multiplexing frequency division multiplexing (communications)(FDM) The simultaneous transmission ofmultiple separate signals through a shared medium (such as awire, optical fibre, or light beam) by modulating, at thetransmitter, the separate signals into separable frequencybands, and adding those results linearly either beforetransmission or within the medium. While thus combined, allthe signals may be amplified, conducted, translated infrequency and routed toward a destination as a single signal,resulting in economies which are the motivation formultiplexing. Apparatus at the receiver separates themultiplexed signals by means of frequency passing or rejectingfilters, and demodulates the results individually, each in themanner appropriate for the modulation scheme used for thatband or group. Bands are joined to form groups, and groups may then be joinedinto larger groups; this process may be consideredrecursively, but such technique is common only in large andsophisticated systems and is not a necessary part of FDM. Neither the transmitters nor the receivers need be close toeach other; ordinary radio, television, and cable service areexamples of FDM. It was once the mainstay of the longdistance telephone system. The more recently developed time division multiplexing in its several forms lends itself tothe handling of digital data, but the low cost and highquality of available FDM equipment, especially that intendedfor television signals, make it a reasonable choice for manypurposes. Compare wavelength division multiplexing, time division multiplexing, code division multiplexing. AcronymsSeefigure of demerit
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