This paper presents a novel load modulation network to realize a broadband Doherty power amplifier (DPA). The proposed load modulation network consists of two generalized transmission lines and a modified coupler. A comprehensive theoretical analysis is carried out to explain the operation principles of the proposed DPA. The analysis of the normalized frequency bandwidth characteristic shows that a theoretical relative bandwidth of approximately 86% can be obtained across a normalized frequency range of 0.4–1.0. The complete design process that allows the design of the large-relative-bandwidth DPA based on derived parameter solutions is presented. A broadband DPA operating between 1.0 GHz and 2.5 GHz was fabricated for validation. Measurements demonstrate that the DPA can deliver an output power of 43.9–44.5 dBm with a drain efficiency of 63.7–71.6% in the 1.0–2.5 GHz frequency band at the saturation level. Moreover, a drain efficiency of 45.2–53.7% can be obtained at the 6 dB power back-off level.

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This paper proposes a broadband high-efficiency power amplifier using an improved continuous mode design. A tuning parameter is introduced into the current expression of the drain to purposely introduce more sine components. These sine components extend the impedance space of the traditional continuous mode, provide greater flexibility in the design of the broadband output matching network, thereby widening the operating bandwidth. Moreover, since no overlap between the current sine components and the voltage cosine components are produced, these sine components do not degrade the PA's efficiency, unlike traditional continuous-mode PAs that often trade efficiency for bandwidth. To validate our approach, a broadband highefficiency power amplifier is designed using GaN HEMT. Measurements indicate that output power is between 40.8 dBm and 42.3 dBm, and the drain efficiency varies from 72.7%-81.8% in 1.5-2.5 GHz, while the gain is between 11.3 dB and 13.0 dB in the same frequency range.