A 1.8–3.8-GHz Power Amplifier With 40% Efficiency at 8-dB Power Back-Off

This paper presents a novel power combining architecture, referred to as distributed efficient power amplifier (DEPA) that mitigates the inherent bandwidth limiting factors in a Doherty power amplifier (DPA), namely, impedance inversion and load modulation, by distributing the conventional auxiliary amplifier of the DPA to multiple auxiliary subamplifiers along a broadband multisection impedance transformer. The proposed technique is demonstrated through the design, implementation, and measurement of a wideband DEPA having 8-dB output power back-off and 72% fractional bandwidth. The experimental results show a Doherty-like efficiency enhancement from 1.8 to 3.8 GHz. For the output power levels of 37.4±1.1 and 45.4±1.1 dBm, corresponding to 8-dB OBO and peak output power, the efficiency levels are between 41%-51% and 42%-62%, respectively. Furthermore, linearized modulated measurements show that the DEPA is linearizable and meets the spectral requirements for modern wireless communication systems.