What is the purpose of a guard band in a frequency division multiplexed system?

In a frequency division multiplexed (FDM) system, the primary purpose of a guard band is to prevent interference between channels. A guard band is an unused frequency range that exists between two or more channels that are actively being used to transmit signals. By providing this buffer zone, the guard band helps to ensure that the signals do not overlap and cause crosstalk, which could result in degraded quality of the transmitted information.

Interference can occur when channels are placed too closely together in the frequency spectrum, particularly in environments where there may be other electromagnetic signals present. The guard band thus serves as a protective measure, ensuring that each channel maintains a clear and distinct frequency range, which is essential for reliable communication and data integrity within the FDM framework.

Increasing bandwidth is not the objective of a guard band, nor does it amplify frequencies or enhance signal strength; those functions relate more to the specific needs of signal processing and transmission technology rather than the structural organization required in FDM systems to mitigate interference.