Precision DPD measurements and modeling of non-linear amplifiers

Amplifiers requiring DPD are typically modeled using Vector Signal Generators and Vector Signal Analyzers, but performance is limited by the VSG signal quality and the VSA noise floor, plus interactions with cables, booster amplifiers, phase-noise from both the VSG and VSA. We introduce a new system, we call precision DPD, utilizing a Vector Network Analyzer with Direct Digital Synthesis to generate the DPD signal and measure the non-linear characteristics at the output of the amplifier. Using vector error correction to remove errors associated with mismatch, and multi-receiver architecture to remove non-linear errors of the VSG source, along with coherent vector averaging to remove effects of the noise floor in the receivers, with clock-locked DDS signal sources derived from a single high-performance fixed microwave clock signal, this system can produce precise DPD models well beyond the current state-of-the-art in terms of residual ACPR, EVM and normalized mean-square error (NMSE).