Frequency Division Multiplexing or FDM
Frequency Division Multiplexing ( FDM )
FDM is an analog technique,where each communication channel is assigned a carrier frequency.To ensure the channels do not interfere a guard band is used in between them.
Multiplexing in FDM
Each sending device generate a signal of similar frequency range. Inside the multiplexer these similar signals are modulated on to different carrier frequencies. The resulting modulated signals are then combined into a single composite signal and is sent over a shared media link that has enough bandwidth.
Demultiplexing in FDM
The demultiplexer uses a series of filters to decompose the multiplexed signal into its constituent component signals.The individual signals are then passed to a demodulator that separate them from their carriers,and passes them to the waiting receivers.
Applications of FDM
1. AM and FM radio broadcasting : The signals which goes to the air is a combination of all signals.A receiver receives all these signals,but filters(by tuning)only the one which is desired.
2. Television broadcasting
3. First generation of cellular telephones uses FDM.