This article presents a novel method to design the multiband Doherty power amplifier (DPA). It is illustrated that phase periodic matching networks (PPMNs) can be used as multiband impedance inverters, off-set elements, and phase compensators to realize multiband DPAs. Moreover, the number of Doherty operation bands can be further increased by employing the reciprocal gate biases. A six-band dual-mode DPA with 1.8-2.2-/3.9-4.3-GHz operation bands in Mode I and 1.52-1.72-/2.38-2.53-/3.67-3.82-/4.53-4.68-GHz operation bands in Mode II using commercial GaN transistors is designed and implemented to validate the proposed method. The fabricated DPA achieves 8.7-13.5-dB gain and 39.6-41.5-dBm peak output power at all the designed bands. Drain efficiency of 49.2%-54.5% and 42.2%-56.7% is measured at a 6-dB output back-off in Mode I and Mode II, respectively. When stimulated by a five-carrier 100-MHz OFDM signal with a 7.7-dB peak-to-average power ratio (PAPR), adjacent channel power ratio (ACPR) of better than -48.9 dBc can be obtained by the proposed DPA after digital predistortion with 35.5%-50.1% average drain efficiency at 1.65/1.95/2.45/3.75/4.1/4.6 GHz, respectively.

In this paper, an extended Chebyshev function is proposed to adapt the matching condition of the power amplifier (PA) by introducing a new factor. A set of impedance functions can be directly calculated along with the variation of a new variable, and the first element extracted from the functions is distributed in a wide range. In addition, the impedance function whose first element is the closest to the output capacitance of the transistor can be easily read out and selected as the original matching network. The fundamental impedance of the selected function will be reached a good matching state, and the impedances out of band will be on the edge of Smith chart. To achieve better performances, the real frequency technique is applied to adjust the harmonic impedances preventing it from falling into the low-efficiency region. Two PAs with a relative bandwidth of 34% and 75% are implemented to validate the proposed approach.

A passive network possessing an input impedance which is positive real in nature poses difficulties with regard to obtaining an optimal impedance for power amplifiers (PAs) with two uncorrelated frequencies. In this context, this study presents a sub‐optimal dual‐band matching method via real frequency technique. Theoretical analysis is presented for voltage waveform with four independent variables and boundary conditions are given for not lower than zero region. To increase the possibility of acquiring a matching network, a sub‐optimal but broad design space is defined according to acceptable performance. It is more practical to match dual‐band or broadband PAs because a single fundamental harmonic impedance point could be corresponding to a set of the second harmonics in the new design space, vice versa. Thus, the sub‐optimal solution space is bounded from region‐to‐region between the required fundamental and second harmonic impedances. An enhanced cost function based on driving point function that could better describe harmonic impedance mismatching degree is also proposed for harmonics control. Finally, a dual‐band PA is designed to demonstrate the general matching method. The peak efficiency is about 70% and saturated output power is 41 dBm in both bands.

This article presents an analytical and coherent design method for the generalized high-efficiency broadband parallel-circuit (PC) Class-E/F₃ power amplifier (PA). By importing the initial phase shift of the third harmonic and adding series reactive element to the load network, a free design parameter can be defined and the design space of the load network parameters are expanded. The design equations of the idealized waveforms and the optimum values of the load network components are derived in detail, and the performance of the peak drain voltage, maximum operating frequency, and power output capability can be improved. In addition, with the expanding space of load network, the generalized PC Class-E/F₃ structure exhibits broadband capability. A matching method with the real frequency technique (RFT) and the de-embedding technique is presented to design the optimal broadband matching network. To verify the validity of the proposed method, a broadband high-efficiency PA working from 1.7 to 2.6 GHz (fractional bandwidth of 42%) is designed. The experimental results of the fabricated PA present high-efficiency characteristics of 68.5%-81% drain efficiency and 62%-75.8% power-added efficiency with 38.8-40.5 dBm output power over the whole operation bandwidth.

Doherty power amplifier (DPA) has shown great potentials in wireless communication systems. However, the output power and efficiency of a DPA are very susceptible to load mismatch. This paper presents the load mismatch analysis and compensation of coupler-based DPAs leveraging on dual-input and mode reconfiguration techniques. A comprehensive analysis, which takes voltage clipping into consideration, is conducted on a coupler-based dual-input DPA (CBDI-DPA) under load mismatch condition. It is illustrated that the parallel Doherty mode could recover the saturation and back-off drain efficiencies (DEs) for the load mismatch in the left and right half parts of the Smith chart, respectively. And the serial Doherty mode could recover the back-off and saturation DEs for the load mismatch in the left and right half parts of the Smith chart, respectively. As a validation, a CBDI-DPA operating at 2.4 GHz is fabricated and measured in this paper. Under the optimal load impedance condition, the fabricated CBDI-DPA delivers a saturation power of more than 43.5 dBm, a saturation DE of more than 70% and a 6 dB back-off DE of more than 60% in both the parallel and the serial Doherty modes. Meanwhile, the simulation and experimental results demonstrate the proposed method can recover the output power and efficiency of a DPA when the load mismatch is inside the 2:1 VSWR circle.