This Letter presents a new combination of a broadband power amplifier (PA) and an output microstrip hairpin bandpass filter. The filter is designed based on the fifth‐order Chebyshev low‐pass prototype element values. Even–odd mode impedance analysis is used to calculate the filter parameters. Meanwhile, only the fundamental impedance matching is considered for this design. Therefore, a highly selective bandpass response is obtained to provide a spurious‐free fundamental impedance matching. For verification, a broadband PA‐filter component across 1.9–3.1 GHz (48%) is designed and fabricated. Measurements have shown a drain efficiency of 48–56.6% with 39.3–40.5 dBm of maximum output power.

This paper presents a co-design of the second harmonic-tuned broadband power amplifier (PA) in cascade with a stub loaded parallel-coupled lines microstrip bandpass filter. These coupled microstrip lines are bilaterally connected with the shorted stub. Filter parameters are determined by an even-odd mode impedance analysis to ensure the high-selectivity and anti-interference bandpass response. Hence, a proper fundamental and second harmonic impedance matching is realized in the desired regions of the Smith chart. Moreover, an overall circuit size is significantly reduced with easy integration. For validation, the proposed structure is manufactured and tested for a commercial 10-W GaN transistor across 1.6-2.8 GHz (54.5%), with 49.1%-65% measured drain efficiency (DE) and 38-41 dBm of measured output power has been obtained. Also, when this PA-filter circuit is driven by a 5 MHz long term evolution signal with a peak to average power ratio of 8.2 dB, an adjacent channel leakage ratio of lower than -55 dBc is achieved.

This article presents a generalized theory and new design methodology for reverse-load-modulated dual-branch (RMDB) power amplifiers (PAs), which uses a current-biased transistor in the main branch to realize optimal load modulation without using the impedance transformers at the output of the PAs. Consequently, this topology offers a proper load modulation mechanism over a wider frequency bandwidth. Besides, smaller output matching network (OMN) footprint and lower loss are suitable features for monolithic microwave integrated circuit (MMIC) designs. The proposed theory can be applied for symmetrical and asymmetrical designs to realize different output power back-off (OPBO) ranges. The theory and design methodology were used to design the first MMIC RMDB PA. The broad bandwidth of this design (2.6-3.8 GHz) allows it to cover multiple bands in 4th-generation (4G) Long Term Evolution (LTE) and 5th-generation (5G) New Radio (NR) standards. Under continuous wave (CW) excitation, the experimental results show a drain efficiency (DE) higher than 58% at peak output power (POP) and 37% at 9 dB OPBO, over the whole frequency band.

In this letter a novel power divider (PD) structure with uniformed characteristic impedance lines and a fixed isolation resistor equal to source and load impedances has been proposed. Unlike traditional power dividers, the electrical lengths of the uniformed 50 Ω branches are the only parameters that need to be adjusted to achieve any required power division ratios, which makes it a flexible and adaptable layout for most desires. Arbitrary power division ratio, especially large dividing ratio that is difficult to achieve by conventional Wilkinson PD, can be obtained easily by applying the proposed structure. For verification, the measured results of a 2 : 1, a 4 : 1 and a 9 : 1 PDs operating at 3 GHz are shown in this letter.

In this paper, a parallel-circuit (PC) class-EF power amplifier (PA) with a shunt quarter-wave transmission-line for driving signals with arbitrary duty cycles is proposed and investigated. At the particular condition of duty cycle=1/3, the optimum values of the elements in the output network as well as some vital design parameters are analyzed and calculated. In this case, a series of remarkable improvements have been obtained, such as peak drain voltage (Vmax), maximum operating frequency (fmax) and power output capability (cp). To the best knowledge of the authors, in terms of Vmax, fmax and cp, the proposed structure is the best among the published works. At the non-ideal situations, three simulated results about the performance comparison between the proposed PA and other switch-mode PAs are also presented. Furthermore, in order to verify its feasibility, a practical circuit based on a transmission-line compensation topology is derived, designed and fabricated. Finally, at the operating frequency of 3.59 GHz, the excellent performance has been realized with the power-added efficiency (PAE) of 79.9% and output power of 40.7 dBm.

This letter proposes a method to further improve the efficiency of power amplifiers (PAs). A thermoelectric generator is used to harvest the thermal energy produced by the PA and transform it into electric energy. Then, the efficiency of the PA can be improved by feeding the obtained electric energy to the drain power supply via a dc-dc converter. For verification, a 10-W 3.2-3.8-GHz class-F PA for base station applications is built; the generated temperature distribution and the process of energy conversion are evaluated. Cost-effective commercial chips are applied to harvest, transform, convert, and feedback the energies to the drain supply. The measurement results demonstrate an improvement of 1.1% drain efficiency at the peak output.