This article presents a novel methodology for designing a broadband Doherty power amplifier (DPA) with extended output power back-off (OBO) range. A modified load modulation network (LMN) is proposed to enhance the OBO range and the bandwidth of the DPA simultaneously. Analysis is conducted to explore the relationship between the proposed LMN parameters and the broadband performance under various OBO levels. Generalized design formulas of the LMN parameters are then introduced to offer the broadband solution for arbitrary current ratios and OBO levels. An asymmetric DPA is demonstrated and implemented with gallium nitride (GaN) transistors using the proposed approach. The fabricated DPA operates from 1.4 to 2.5 GHz with 9-dB OBO range. The measured drain efficiency reaches 61%-75.5% at saturation and 44.6%-54.6% at 9-dB OBO within the operating bandwidth. When driven by a 60-MHz modulated signal with 9-dB peak-to-average power ratio (PAPR), the fabricated DPA attains 47.4%-53.5% average drain efficiency and better than -45.5-dBc adjacent channel leakage ratio (ACLR) after digital predistortion.

中文翻译：

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利用改进的负载调制网络增强 Doherty 功率放大器的带宽和回退范围


本文提出了一种设计具有扩展输出功率回退 (OBO) 范围的宽带 Doherty 功率放大器 (DPA) 的新颖方法。提出了一种改进的负载调制网络（LMN）来同时增强 OBO 范围和 DPA 的带宽。进行分析以探讨所提出的 LMN 参数与不同 OBO 级别下的宽带性能之间的关系。然后引入 LMN 参数的广义设计公式，为任意电流比和 OBO 水平提供宽带解决方案。使用所提出的方法，使用氮化镓 (GaN) 晶体管演示并实现了非对称 DPA。制造的 DPA 工作频率为 1.4 至 2.5 GHz，OBO 范围为 9 dB。在工作带宽内，测得的漏极效率在饱和时达到 61%-75.5%，在 9dB OBO 时达到 44.6%-54.6%。当由具有 9dB 峰均功率比 (PAPR) 的 60MHz 调制信号驱动时，制造的 DPA 达到 47.4%-53.5% 的平均漏极效率，并且优于 -45.5dBc 的相邻信道泄漏比 (ACLR)经过数字预失真后。