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This article presents a high-efficiency dual-band filtering Doherty power amplifier (DPA) using multi-function circuits for simplifying the structure. A dual-band filtering power combiner also plays the role of real-to-real impedance matching, in which one resonator is shared by both the power combing and filtering circuits. Thus, only one extra resonator is needed for the power combiner to provide second-order dual-band filtering responses, which contributes to high efficiency of the DPA. Transmission zeros are generated between the two passbands, realizing a sharp roll-off rate and greatly enhancing the isolation between the two passbands. Meanwhile, an impedance control network is designed to simultaneously suppress the harmonics and transform the optimized complex impedance desired by the transistor to a real one. In this way, the output matching network and extra filter in conventional design are realized by the filtering power combiner and impedance control network in the proposed design, resulting in a simpler structure. A dual-band DPA operating at 2.14 and 2.6 GHz is implemented with the measured peak efficiencies of 64.4% and 69% at the output power of 43.25 and 43.3 dBm, respectively. The 6-dB back-off efficiencies are 50% and 57% at the two passbands. Under 20-MHz long term evolution (LTE) modulated signals with a peak-to-average power ratio (PAPR) of 7.5 dB, the DPA after digital predistortion (DPD) is measured with an adjacent channel leakage ratio (ACLR) of better than −45.2 dBc and the efficiencies of 51.6% and 54.3% at interested bands. The peak efficiency under the excitation of the concurrent modulated signal is 48.6%. [ABSTRACT FROM AUTHOR]

This brief presents a filter-integrated high-efficiency class-F power amplifier (PA). The hybrid cavity–microstrip filtering circuit is employed not only to realize output impedance matching and the third-harmonic manipulation but also to provide high-selectivity bandpass responses. To fulfill the requirements of high-efficiency class-F PAs, cavity resonators and microstrip feeding structures are involved, and their benefits are fully exploited. The metal cavity resonator features a high $Q$ value and, thus, low loss in the passband, resulting in high efficiency. Moreover, metal walls of cavities act as heat sink for the transistor. The microstrip feeding structures are used to improve the skirt selectivity and manipulate the third harmonic. Moreover, it features easy integration with the transistor, and thus, the transition between cavity and microstrip lines is eliminated. The hybrid filter is characterized based on filter synthesis theory. Complex impedance conversion analysis is carried out to guide the impedance transformation from 50 $\Omega$ to a complex one desired by the transistor. For demonstration, a filtering PA operating at 2.4 GHz is designed and measured. It exhibits both high-selectivity bandpass responses and good PA performance with maximum power-added efficiency of 70.9% at 40.8-dBm output power. [ABSTRACT FROM AUTHOR]

In this letter, a high-efficiency filter-integrated class-F power amplifier (PA) is presented. High-Q-factor dielectric resonator (DR) filter is employed as the output matching network of the class-F PA. Theoretical analysis is carried out to guide the impedance transformation from $50~\Omega $ to that desired by the transistor at the operating frequency and the harmonic ones. Two transmission zeros are generated by the DR filter for realizing good skirt selectivity. Besides, metal cavity of the DR filter acts as heat sink for the transistor. For demonstration, a filter-integrated PA operating at 1.88 GHz is implemented. Comparison is made to show the advantages of this letter. [ABSTRACT FROM PUBLISHER]