Research on Load Modulation Enhancement of Quasi-Ideal Doherty Power Amplifier with Equivalent Transconductance Compensation

HUA Jun; XU Gaoming; CHEN Jinghao; LU Siyang; YOU Leiyuan; LÜ Yan; LI Gang; SHI Weimin; LIU Taijun

doi:10.11999/JEIT250789

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HUA Jun, XU Gaoming, CHEN Jinghao, LU Siyang, YOU Leiyuan, LÜ Yan, LI Gang, SHI Weimin, LIU Taijun. Research on Load Modulation Enhancement of Quasi-Ideal Doherty Power Amplifier with Equivalent Transconductance Compensation[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250789

Citation:

HUA Jun, XU Gaoming, CHEN Jinghao, LU Siyang, YOU Leiyuan, LÜ Yan, LI Gang, SHI Weimin, LIU Taijun. Research on Load Modulation Enhancement of Quasi-Ideal Doherty Power Amplifier with Equivalent Transconductance Compensation[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250789

Citation:

HUA Jun, XU Gaoming, CHEN Jinghao, LU Siyang, YOU Leiyuan, LÜ Yan, LI Gang, SHI Weimin, LIU Taijun. Research on Load Modulation Enhancement of Quasi-Ideal Doherty Power Amplifier with Equivalent Transconductance Compensation[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT250789

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Research on Load Modulation Enhancement of Quasi-Ideal Doherty Power Amplifier with Equivalent Transconductance Compensation

doi: 10.11999/JEIT250789 cstr: 32379.14.JEIT250789

1.
School of Information Science and Engineering, Ningbo University, Ningbo 315211, China
2.
School of Microelectronics and Communication, Chongqing University, Chongqing 400044, China

Received Date: 2025-08-25
Accepted Date: 2025-12-12
Rev Recd Date: 2025-12-11

Available Online: 2025-12-19

Abstract

Abstract

Objective Modern wireless communication systems require efficient dynamic-range performance in RF power amplifiers. The Doherty Power Amplifier (DPA), which uses dynamic load modulation between the main and auxiliary paths, achieves high efficiency at power backoff. It is widely applied in multi-carrier 4G and 5G macro base stations. Research on DPAs generally focuses on improving backoff efficiency, backoff range, and bandwidth. However, the architecture has a structural limitation because the auxiliary amplifier, biased in Class C, exhibits weak current output compared with the main amplifier biased in Class AB. The low conduction level and short turn-on period of the auxiliary path create nonlinear imbalance and reduce overall performance. Methods The study addresses insufficient load modulation caused by the weak current output capability of the auxiliary amplifier. An equivalent transconductance compensation theory is proposed. It compensates the current of the auxiliary amplifier under Class C bias by injecting a compensatory current into the branch. A load-modulation-enhanced quasi-ideal high-performance DPA is developed to resolve the inherent current deficiency in the auxiliary path of traditional configurations. Results and Discussions A load-modulation-enhanced DPA was designed and fabricated using the GaN HEMT device CG2H40010F for the 1.3$ \sim $1.8 GHz band. Measurements show that the saturated output power ranges from 43.7 to 44.5 dBm and that the Drain Efficiency (DE) exceeds 69.1%. At a 6 dB backoff, the DE remains between 62.9% and 69.4% and the gain ranges from 9.7 to 10.5 dB. At a 9 dB backoff, the DE ranges from 49.5% to 57% and the gain ranges from 10.3 to 11.5 dB. The equivalent transconductance compensation theory resolves the load modulation bottleneck of traditional DPA structures through the current-injection mechanism. It provides meaningful guidance for broadband RF power-amplifier design with high backoff efficiency. Conclusions The study proposes an equivalent transconductance compensation method by adding a third compensation branch to the traditional DPA structure. This mechanism corrects the weak auxiliary-amplifier current caused by Class C bias and its short turn-on period, thereby achieving a quasi-ideal load-modulation-enhanced DPA. A device operating from 1.3 to 1.8 GHz was designed to validate the method. The measured saturated DE exceeds 69.1%. The DE ranges from 62.9% to 69.4% at a 6 dB backoff and from 49.5% to 57% at a 9 dB backoff. The linearized Adjacent Channel Leakage Ratio (ACLR) is lower than –49 dBc. These results verify the feasibility of the method and show strong application potential.
- Doherty power amplifier,
- Active load modulation,
- Compensation branch,
- High efficiency

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References(16)

References

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