1 GHz Instantaneous Bandwidth Digital Pre-Distortion for Multi-Concurrent Channel Wideband Power Amplifiers

This paper presents an extremely broadband digital predistortion linearization (DPD) technique that uses an adaptive Volterra-based model of the nonlinear distortion transfer function. The model is parameterized to accommodate higher order terms as necessary to accurately approximate the actual broadband nonlinear transfer function. The algorithm uses matrix and tensor factorizations to significantly simplify the complexity of the hardware implementation by identifying and removing mathematical redundancy and ignoring the components of the model that have negligible impact on the performance. This results in fewer multiplications and allows the addition of higher order terms to the model without the exponential growth in complexity. Polyphase filtering techniques are also used to run these operations in parallel which allows very broadband operation using signal processing operating at much lower data rate commensurate with the capabilities of off the-shelf FPGAs. Measured results of the linearization technique are presented for multi-carrier concurrent waveforms into a 100 W GaN power amplifier showing an improvement in intermodulation products of more than 30 dB over an instantaneous bandwidth of 1 GHz. To our knowledge, this is far higher instantaneous bandwidth than other wideband DPD linearization techniques published in the literature.