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 characterization and digital predistortion. The proposed measurement procedure relaxes significantly the sampling rate requirement on the analog to digital converters of the feedback path. Successful PA linearizations were achieved in the presence of 20 MHz, 40 MHz, and 60 MHz LTE-A signals using a vector signal analyzer with sampling speeds equal to only 24 Msps, 40.96 Msps, and 61.44 Msps, respectively. Despite these very low sampling rates, a quasi perfect 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 correction bandwidth is much wider than the observation bandwidths associated with the receiver sampling rates.