A Digital Post-Distortion Procedure for Improving the Accuracy of Ultra-Wideband RF Frontends

In this paper, a characterization and post-distortion procedure is presented that lends well, but is not limited, to the restrictions of a high-speed waveform capture setup with 4.8 GHz input bandwidth. The capture setup contains a high-bandwidth differential amplifier, commonly used in ADC drivers, which can exhibit considerable distortion when the input signals approaches the upper frequency limit. The inverse Volterra series representation of the setup is obtained and then used to reconstruct the input signal from its distorted output. System characterization makes use of the Multivariance method [1], extended by a new higher-order decorrelation algorithm, that enables the use of non-white and nonlinearly distorted input noise; making the Multivariance method applicable for RF systems while preserving its advantages. The results are experimentally verified, and some notes are given on the practical implementation.