Dual-Band 3-Way Doherty Power Amplifier With Extended Back-Off Power and Bandwidth

This paper presents an energy-efficient dual-band 3-way Doherty power amplifier (DPA) suitable for wireless infrastructure that transmits intra-band and inter-band carrier aggregated communication signals with high peak-to-average power ratios. The paper begins with a bandwidth analysis of dual-band impedance inverting networks, especially when used to absorb the transistors’ output capacitances. This analysis produced a set of equations which directed the synthesis of a dual-band 3-way DPA combining network capable of producing the proper load modulation over an extended output back-off while maintaining acceptable fractional bandwidth. A 60-watt dual-band 3-way DPA was designed as a proof-of-concept demonstrator to operate in two bands, 2.0-2.2 GHz and 3.3-3.6 GHz. Under continuous wave stimuli, drain efficiencies of about 48% and 43% were recorded at an output back-off of 9dB in the two bands. These efficiencies were maintained over a fractional bandwidth of about 10%. The linearizability of the fabricated DPA using digital pre-distortion techniques was also confirmed under intra-band and inter-band carrier-aggregated signals.