2-W Broadband GaN Power-Amplifier RFIC Using the $f_{T}$ Doubling Technique and Digitally Assisted Distortion Cancellation

The method of derivative superposition is enhanced with digital techniques to cancel the intermodulation distortion generated by a 2-W power amplifier (PA) RF integrated circuit over a broad band of 6 GHz. Two amplifiers were fabricated and tested: a baseline PA without distortion cancellation and a PA with digitally assisted distortion cancellation to demonstrate the effectiveness of the new technique. The PAs are biased in class-A mode and have an OP_1dB of 31 dBm and a P_SAT of 33 dBm. Measurements reveal that the output third-order intercept point (OIP3) of the PA with digitally assisted distortion cancellation can be increased to 50.25±3.75 dBm between 1-6 GHz relative to the OIP3 of the baseline PA, which is 40.25±2.75 dBm over the same frequency span. The level of distortion cancellation is not only dependent on the frequency of the incident signal, but also on its power level. Data is presented that shows how the proposed digitally assisted distortion cancellation method also improves the OIP3 of the PA when the RF input power level is taken into account.