Harmonic‐tuned continuum mode active load modulation output combiner for the design of broadband asymmetric Doherty power amplifiers

Abstract

The conventional Doherty output combiner limits the bandwidth of operation in the asymmetric Doherty power amplifiers (DPAs). In this study, an output combiner that is designed using a harmonic‐tuned continuum mode active load modulation technique is proposed with the main target of extending the bandwidth of operation in the asymmetric DPAs. Through this methodology, design equations are derived and multiple harmonic impedance solutions are provided. This offers greater freedom for designing the output combiner of the asymmetric DPA which consists of the impedance inverting network and the impedance transforming network. Moreover, enhancements in the efficiencies at back‐off and saturation power levels are made possible. The efficacy of the design strategy is demonstrated by the realised broadband asymmetric DPA prototype working within the band of 1.4–2.45 GHz. The experimental results have shown 54.55% bandwidth of operation, accounting for about 0.95–12.55% increment in bandwidth as compared with some recently published DPAs in the literature. Substantially, drain efficiencies within 35.5–52% at 6 dB output power back‐off level and 47.5–64.2% at peaking power level are also recorded from the experiments. The maximum output power and gain are recorded at 43.52 dBm and 13.03 dB, respectively.

Current State and Advanced Architectures of Doherty Power Amplifiers

“…Fig. 1 Typical DPA schematic diagram [3]. Thus, a low back-off Rcarrier impedance Doherty structure is needed.…”

Broadband Class-J GaN Doherty Power Amplifier

“…Moreover, in order to enhance PA performance, harmonic tuning techniques have been considered so far [32][33][34], but most of them suffer from bandwidth limitations. The class-J PA shows wide bandwidth compared to other harmonic-tuned PAs [35][36][37], while its sensitivity to harmonics of the matching network is lower than class F [38,39].…”

Design of a Wideband Doherty Power Amplifier with High Efficiency for 5G Application

“…However, while the wider RF bandwidths achievable in the FR2 range allow relaxing the complexity of the adopted modulation schemes, PAs working in the FR1 range need to operate as efficiently as possible with modulations as complex as 4096-Quadrature Amplitude Modulation (QAM). These kinds of modulations feature a time-varying envelope with a very high peak-to-average power ratio (PAPR); therefore, to cope with such signals, power amplifiers are required to have high efficiency, not only at saturation, but also at lower output power levels [10][11][12][13]. This is not the case for conventional power amplifiers, which can have very high efficiency at their maximum output power, but show a sharp efficiency drop with output power back-off [14].…”