A low-rate identification method for digital predistorters based on Volterra kernel interpolation

RF power amplifiers (PA) of wireless communication systems are usually driven in their nonlinear region to obtain a higher efficiency. The price paid for the increased efficiency is the distortion of the transmission signal. To fulfil a given spectral mask for the transmission signal and to avoid an unacceptable high bit-error rate on the receiver side, the amplifier must be linearized. It is well known that nonlinear system identification (PA or predistorter) can be accomplished on the Nyquist-rate regarding the input signal bandwidth. However for predistortion applications, systems operating on the output signal Nyquist-rate are required. In this paper we show how such predistortion systems can be obtained by a multi-dimensional Volterra kernel interpolation where the kernels are estimated on a Nyquist-rate regarding the input signal, without the demand for an expensive high sampling rate analog to digital converter (ADC).