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In this study, a methodology is proposed for extending the high‐efficiency power range (HEPR) of symmetrical Doherty power amplifiers (DPAs). This method takes advantage of the output impedance of peaking stage. Traditional symmetrical DPAs maintain high efficiency over a 6 dB power range with an assumption of the output impedance of peaking stage being infinity. This study reveals that the HEPR can be further enhanced by tuning the output impedance of peaking stage away from infinity and changing the phase delay of the impedance inverter after carrier power amplifier. A 2.2–2.3 GHz symmetrical DPA with an HEPR of 9 dB is fabricated to validate our theory. The experimental results possess drain efficiencies of 45.3–49.5% at 9 dB output power back‐off level and 62.9–71% at peaking power level over 2.2–2.3 GHz. The maximum output power of the fabricated DPA is 45 dBm with a gain of 11.6–13.5 dB across 2.2–2.3 GHz.

Achieving a fractional bandwidth (FBW) of more than 60% has been a challenging problem for two-way symmetrical Doherty power amplifiers (TW-SDPAs) that are designed using continuous mode technique. As reported in the literature, these designed continuous mode-based TW-SDPAs possess less than 52% FBW which cannot satisfactorily meet the challenging, complex and ever-evolving modulation schemes' demands. To overcome such a limitation, this paper proposes a novel approach based on fuzzy logic techniques able to simplify and to speed up the design of continuous mode-based TW-SDPAs with state-ofart FBW. In particular, the proposed technique uses K-means unsupervised learning clustering algorithm and continuous mode technique in a modelled fuzzy logic system environment. As a result, extensive impedance solution design space is readily made available and the optimal impedances required by the carrier and peaking sub-amplifiers for efficiently operating at the saturation and output-power-back-off (OPBO) levels are automatically obtained. For verification, a TW-SDPA was designed and measured. According to the measured results, the TW-SDPA operates within 1.2−2.4 GHz frequency band, corresponding to 66.7% FBW. As compared to the designed continuous modebased TW-SDPAs reported in the literature, this work indicates over 15% increment in FBW. Moreover, 41.59%−81.1% drain efficiency (DE) at saturation, 35%−63% DE at 6 dB OPBO, 42−45 dBm output power and 7−10.52 dB gain were successfully achieved. Adjacent channel leakage ratio (ACLR) better than −46 dBc and average DE within 46%−55% were successfully recorded after linearisation.Index Terms-Continuous mode, Doherty power amplifiers (DPAs), fuzzy logic technique, fractional bandwidth (FBW).

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