Mumbai university > Comp > SEM 8 > Mobile Communication

Marks: 5M

Year: Revised 2012

• In FDMA system many channels share the same antenna at the base station. The power amplifiers or the power combiners, when operated at or near saturation for maximum power efficiency are non-linear.

• Nonlinearities cause signal spreading in the frequency domain and generate intermodulation frequencies.

• IM is undesired RF radiation which can interfere with other channels in FDMA systems,

• Spreading of the spectrum results in adjacent channel interference.

• Intermodulation is the generation of undesirable harmonics. Harmonics generated outside the mobile radio band cause interference to adjacent services, while those present inside the band cause interference to other users in the wireless system.

• To minimize the effects of intermodulation distortion, stringent RF filters are required to reject inter modulation distortion. RF filters are heavy and costly.