A wideband two‐stage Doherty power amplifier at high back‐off by exploring feasible design space

Abstract

This article explores a design space for bandwidth enhancement of two‐stage Doherty power amplifier for higher back‐off based on same devices. This design space analysis shows that for any back‐off level, a number of bandwidth enhancement solutions can be obtained with various combinations of design parameters for load combiner and load impedance. Therefore, the proposed scheme explores design space in terms of optimum design parameters for load combiner and load impedance for best bandwidth and realizability at a high back‐off. The proposed design methodology is validated with a two‐stage Doherty power amplifier using 25 W packaged Gallium Nitride High Electron Mobility Transistors. This Doherty power amplifier provides measured drain efficiency between 66% to 73.8% at saturation and 45% to 63.6% at 8‐9 dB output power back‐off from 1.7 to 2.025 GHz. Measurement with WCDMA signals shows that the adjacent channel power ratio is better than −46 dBc after applying digital predistortion.

Hybrid Analog/Digital Continuous Class B/J Mode for Broadband Doherty Power Amplifiers

“…The previous section describes the design methodology of a broadband load combiner. In case of a fully analog DPA architecture, the phase offset added by the phase difference between the two branches of the load combiner is compensated by offset lines at the input of main and auxiliary PAs [9], [10], [13], [15]. However, the two amplifiers used in main and auxiliary branches have different class of operation which results into inappropriate power combining at the output of load combiner.…”

Efficiency‐enhanced Doherty power amplifier using Chireix‐like compensation technology

“…The development of mobile communication technology, for instance the upcoming 5G applications, sets higher requirements on drain efficiency for power amplifiers. Doherty power amplifiers are high in efficiency at the back‐off power range due to the presence of active load modulation, which is suitable for fifth‐generation mobile communications with high peak to average power ratio (PAPR) modulation signals . Therefore, Doherty has attracted researchers' attention for decades.…”