Minimization of the Intermodulation Distortion of a Nonlinearly Amplified OFDM Signal

In the course of development of the HIPERLAN-Standard OFDM (Orthogonal Frequency Division Multiplexing) was a possible candidate for the modulation scheme.An advantage of OFDM is that it can be implemented simply and that it is suitable for the transmission of high data rates in the mobile radio channel. Furthermore, it is insensitive against disturbances caused by multipath propagation. However, the OFDM signal shows a nonconstant envelope that leads to unwanted out-of-band radiation, in case the transmitter amplifier has a nonlinear characteristic.In this paper a method for the reduction of the fluctuation of the envelope of an OFDM signal is presented. Combined with a predistortion to linearize the characteristic of the transmitter amplifier an efficient method for the reduction of the out-of-band radiation results so that OFDM could prove to be a suitable modulation scheme for future mobile telecommunication applications.