Predicting spectral regrowth of power amplifiers in OFDM systems

The (orthogonal frequency-division multiplexing) OFDM signal is vulnerable to nonlinearities (such as power amplifier nonlinearities) in communication channels. Therefore, understanding how the channel nonlinearities distort the OFDM signal is essential to the success of an OFDM system. In this paper, we derive a closed-form expression for the spectrum of the OFDM signal at the power amplifier output in terms of power amplifier parameters and the higher-order statistics of the OFDM signal. This expression can be used to predict the spectral regrowth of the OFDM signal caused by power-amplifier nonlinearities. This problem is important because it can help to foresee whether the power amplifier is suitable for the application under consideration without actually conducting expensive experiments. Computer simulation is conducted to justify the goodness of the proposed prediction method. The result indicates that the proposed method can provide a simple yet accurate way for predicting the spectral regrowth.