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An optimal balance between high efficiency and high linearity is one of the main performance metrics of modern base stations to handle the deep compression of the power amplifier (PA) module. In principle, the plethora of amplitude‐to‐amplitude (AM‐AM) and amplitude‐to‐phase (AM‐PM) distortions are issues worth exploring. Therefore, this paper presents a linearized harmonic‐tuned PA that operates at 2.4 GHz. The presented PA utilizes a compact input matching network (IMN) and output MN (OMN) with shunt‐connected tunable resonant circuits augmented by the stabilization network, whose presence greatly reduces the transistor parasitics and high‐order effects. Hence, a joint embodiment of each other gives optimal fundamental impedance matching alongside harmonic terminations and precise AM/PM waveform properties. The measurement results have shown that the fabricated PA exhibits peak saturated output power of 40.9 dBm and peak drain efficiency (DE) of 67%. In addition, the AM‐AM and AM‐PM curves under continuous‐wave excitation yield a gain flatness of 0.5 dB over a 37.5 dBm power range and ±3.5° phase distortion, respectively, when the input power level is swept up to the saturation level of 40 dBm. When driven with a 5 MHz 64‐QAM OFDM signal and 6.9 dB power back‐off, the manufactured PA meets the adjacent channel leakage ratio specification of −30 dBc at an average output power of 34.5 dBm. [ABSTRACT FROM AUTHOR]

This article presents a broadband fully integrated Doherty power amplifier (DPA) using a continuous-mode combining load. It is illustrated that the continuous-mode impedance condition in back-off and saturation for Doherty operation can be achieved with a simple impedance inverter network (IIN) that can be realized using lumped components in gallium nitride (GaN) monolithic microwave integrated circuits (MMICs). A DPA was designed and fabricated using the 250-nm GaN process to validate the proposed architecture and design methodology. The fabricated DPA chip attains around 8 W saturated power from 4.1 to 5.6 GHz. About 38.5%–46.5% drain efficiencies are achieved at 6-dB output power back-off within the entire design band. When driven by a 100-MHz OFDM signal with 6.5-dB peak-to-average power ratio (PAPR), the proposed DPA achieves better than −45-dBc adjacent channel leakage ratio (ACLR) and higher than 38% average efficiency at 4.4 and 5.2 GHz after digital predistortion. [ABSTRACT FROM AUTHOR]

An under-sampling digital predistortion based on a multi-tone mixing feedback technique (MTM-DPD) is presented in this article. In contrast to the under-sampling digital predistortion (DPD) based on conventional receivers, the proposed method could simultaneously reduce the sampling rate and acquisition bandwidth using a multi-tone mixing (MTM)-based feedback channel. The MTM-DPD is implemented with an evolved direct learning architecture, where the coefficients of a predistorter are estimated based on the aliased feedback signal, preprocessed input signal, and preprocessed kernels of the DPD model. To preprocess the input signal and kernels, the behavioral model of the MTM-based feedback channel and its corresponding identification algorithm are analyzed in detailed. Experimental results show that for a gallium nitride (GaN)-based power amplifier (PA) with 40-MHz input, under the excitation of a 17 tone LO signal with frequency interval 7.68 MHz, the MTM-DPD with sampling rate 15.36 MSPS and acquisition bandwidth 15.36 MHz could improve the adjacent channel power ratio (ACPR) from −30.1 to −46.5 dBc and the error vector magnitude (EVM) from 9.13% to 1.76%. Compared with the conventional full sampling DPD (FS-DPD), the MTM-DPD could reduce the cost of analog-to-digital converters (ADCs) in feedback channel significantly while maintaining satisfactory linearization performance. [ABSTRACT FROM AUTHOR]

In this article, a design method for a tri‐band power amplifier (PA) with dynamic drain bias voltage is presented. Continuous operation modes are used to expand the impedance design space. In the input and output matching networks, harmonic control circuits are set up to improve efficiency. The load harmonic impedances are obtained by continuous theory. Bias network and harmonic short circuit are used in the input matching network to control harmonics and obtain stop‐band. Dynamic drain bias enables the PA to adapt to different emission environments. With input and output harmonic control technology, a 0.9, 1.5, and 2.1 GHz GaN PA is designed to achieve high efficiency in different modes. The measured efficiencies of the fabricated PA at all three bands are more than 58.6%. At 1.5 GHz, when driven with a 20 MHz LTE signal with a 7 dB peak‐to‐average power ratio, by applying digital pre‐distortion, the PA prototype maintains an adjacent channel power ratio of better than −48.7 dBc. [ABSTRACT FROM AUTHOR]