Reconfigurable Doherty Power Amplifier for Multifrequency Wireless Radio Systems

This paper proposes a frequency-agile Doherty amplifier capable of efficiently amplifying multiband wireless signals located at widely spaced frequencies. Starting with the study of the load modulation concept in the Doherty technique and the various frequency-dependent components involved in its realization, this paper suggests a simplified and effective design methodology for the development of frequency-agile and reconfigurable Doherty amplifiers using a small number of electronically tunable devices. As a proof of concept, a reconfigurable Doherty power amplifier (PA) prototype is designed and fabricated to operate at 1.9, 2.14, and 2.6 GHz. The measurement results obtained using a continuous-wave signal revealed drain efficiencies of approximately 70% and 60% at the peak power and 6 dB back-off power, respectively, for the three targeted operating frequencies. In addition, the reconfigurable Doherty amplifier was successfully linearized when driven with 20-MHz wavelength code-division multiple access and longterm evolution signals, using a Volterra-based digital predistrtion algorithm which exploits a pruned Volterra series.