Modelling of power amplifier nonlinearities using Volterra series

Radio Frequency (RF) power amplifiers (PAs) are one of the mostimportant elements in radio telecommunication facilities, which are used to amplifythe power of input signals. At the same time, they gradually become the bottle-neck for modern telecommunication systems due to the conflict between thelinearity and the efficiency, resulting in their relatively high level energy consump-tion. Volterra kernels are naturally good representations of intermodulation andharmonic distortions, the main distortions in typical power devices, because oftheir convolutional structures. Some work has been done to model the distortionsby using Volterra series. However, Volterra series expansions are usually truncatedseverely, due to complexity of computation, so that they do not give accuraterepresentations of the original system. It is intended ultimately to apply a time-invariant, discrete-time Volterra series method in the modelling of RF powerampli¯ers to assess distortion levels to eliminate or reduce them. Owing to ourlimited computational facilities, the experimental PA in this preliminary work isonly excited in a moderate frequency range, 100Hz to 1kHz.