Extending the Characterization Bandwidth of Dynamic Nonlinear Transmitters With Application to Digital Predistortion

This paper reports a new measurement method for wideband radiofrequency power amplifier (PA) characterization and digital predistortion. The proposed measurement procedure significantly relaxes the sampling rate requirement on the analog-to-digital converters of the feedback path. Successful PA linearizations were achieved in the presence of 20, 40, and 60-MHz LTE-A signals using a vector signal analyzer with sampling speeds equal to only 24, 40.96, and 61.44 Ms/s, respectively. Despite these very low sampling rates, a quasiperfect cancellation of the PA distortions was achieved (more than 50 dBc in terms of ACLR), in all tests, over bandwidths including up to fifth-order intermodulation distortions. Such a correction bandwidth is much wider than the observation bandwidths associated with the receiver sampling rates.