The present paper proposes an optimization design method for the Doherty output matching network (OMN) using impedance–phase hybrid objective function constraints, which possesses the capability of enhancing the efficiency consistency of the Doherty power amplifier (DPA) using integrated enhancing reactance (IER) during the back-off power (BOP) range. By calculating the desired reactance for an extended BOP range and combining it with the two-impedance matching method, the S -parameters of the OMN are obtained. Meanwhile, the impedance and phase constraints of the OMN are proposed to narrow the distribution range of the IER. Furthermore, a fragmenttype structure is employed in the OMN optimization so as to enhance the flexibility of the circuit optimization design. To validate the proposed method, a 1.7–2.5 GHz symmetric DPA with a large BOP range was designed and fabricated. Measurement results demonstrate that across the entire operating frequency band, the saturated output power is >44 dBm, and the efficiency ranges from 45% to 55% at a 9-dB BOP.

This article proposes a design and optimization method for Ultra-Wideband power amplifiers (PAs) using improved multiobjective evolutionary algorithm based on decomposition (MOEA/D) and mixed optimization objective function (MOOF). In order to address the insufficient optimization capabilities of conventional MOEA/D algorithm when dealing with complex Pareto fronts, the optimization algorithm is improved by using adaptive weights, neighborhoods, and global replacement. Initially, based on the sparsity of the population and an external population, the weight vectors corresponding to invalid or crowded individuals in the population are replaced. And, the neighborhoods are adaptively adjusted based on the number of iterations and the sparsity of each individual. Then, a global replacement is employed to accelerate the convergence process. Moreover, a MOOF using the load impedance, output power, efficiency and gain is conducted in the PA optimization design. To reduce the difficulty of impedance judgment, a construction method of impedance solution set based on Poisson disk sampling has been proposed and employed for optimization. For validation, an Ultra-Wideband PA operating at 100–4000 MHz (190.2% fractional bandwidth) was designed and optimized. Measured results show a drain efficiency ranging from 56.0% to 70.9% with an output power higher than 39 dBm at saturation within the whole operational frequency band.

In this paper, a multi-channel 5G millimeter wave array is presented, operating between 24.25 and 27.5 GHz. The array is composed of array antenna and multi-channel radio frequency (RF) front-end, which utilizing 4-channel mixer chips to achieve brick-shaped massive MIMO array design. It supports wide band signal transmission and is suitable for fully digital beamforming (DBF) architecture. Besides, a 5G millimeter array testing platform based on intermediate frequency (IF) phase control and mechanical turntable is built to verify the performance of beam scanning. The measured gain achieves over 14.2dB and the error vector magnitude (EVM) of 5G NR signal is lower than 1.07%. Beam scanning patterns demonstrate that the 5G millimeter wave array can cover ±30° region. This multi-channel array provides a foundation for 5G millimeter wave fully digital massive MIMO transceiver implementation.

In this paper, a highly efficient gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) Doherty power amplifier (DPA) from 4.6 to 5.5 GHz with the consideration of the influence of the peaking transistor’s output capacitor$(C_{\mathrm {out}}$) operated in Class-C state is presented. Based on the load-modulation behavior analysis, the effect of the$C_{\mathrm {out}}$of the peaking transistor on the performance of the wideband DPA has been theoretically analyzed for the first time by directly evaluating the value of the peaking transistor’s$C_{\mathrm {out}}$. A hybrid matching technique has been proposed to ensure that the DPA can realize a proper load-modulation with high back-off efficiency in a wide bandwidth. In this method, the peaking transistor is matched using a simple T-shape band-pass type network with the$C_{\mathrm {out}}$of the peaking transistor in Class-C operation state compensated properly, while the carrier transistor is matched using a 2-point matching method. For verification, a wideband GaN MMIC DPA with the frequency range of 4.6 to 5.5 GHz was designed using a 0.25-$\mu {\mathrm{ m}}$GaN on silicon-carbon high-electron-mobility transistor process. Experimental results show that the fabricated DPA can realize the output power of 41.1-41.6 dBm and the drain efficiency (DE) of 57.6%-63.3% at saturation in the whole frequency band. The measured DE at 6-dB power back-off is 51%-56.4%. Good linearity with high average efficiency performance was obtained when excited by a 160-MHz modulated signal after linearization.

A symmetric Doherty power amplifier (DPA) based on integrated enhancing reactance (IER) was proposed for large back‐off applications. The IER was generated using the peaking amplifier with the help of a desired impedance transformation in the low‐power region to enhance the back‐off efficiency of the carrier amplifier. To convert the impedances properly, both in the low‐power region and at saturation, a two‐impedance matching method was employed to design the output matching networks. For verification, a symmetric DPA with large back‐off power range over 2.2–2.5 GHz was designed and fabricated. Measurement results show that the designed DPA has the 9 dB back‐off efficiency of higher than 45%, while the saturated output power is higher than 44 dBm over the whole operation bandwidth. When driven by a 20 MHz LTE signal, the DPA can achieve good average efficiency of around 50% with adjacent channel leakage ratio of about –50 dBc after linearization over the frequency band of interest. The linearity improvement of the DPA for multistandard wireless communication system was also verified with a dual‐band modulated signal.

A novel digital predistortion (DPD) technique is proposed to linearize ultra‐broadband millimeter wave (mmWave) power amplifiers (PAs) by only employing very limited bandwidth resources for the Tx, feedback loop (FB), and baseband (BB). Compared to the conventional methods, the proposed method will comprehensively reduce the bandwidth requirements for the whole system, which will make the linearization affordable for mmWave PAs. To validate the proposed idea, a 4‐carrier 320 MHz modulated signal was employed to excite a mmWave PA with the center frequency of 41 GHz. Experimental results have proven that the proposed method can effectively realize the PA linearization with very narrow Tx/FB/BB bandwidth, which largely extends the capability of DPD to the forthcoming 5G era.