Millimeter wave full-digital full-connected multibeam array can play a crucial role in meeting the massive data capacity demands for the future Internet of Things. In this paper, a novel digital predistortion (DPD) technique is designed to linearize this array for the scenario under constraint bandwidth. Two different linearization schemes, including beam-oriented DPD schemes and PA-oriented DPD schemes, are analyzed and compared, along with their respective applicable scenarios. Based on the characteristics of full-digital full-connected arrays, and by fully leveraging the alleviation of adjacent channel power ratio metrics requirement in FR2 band specification, the band-limited DPD concept can be effectively integrated into the full-digital full-connected multibeam array architecture, which allows for the array linearization with low system bandwidth requirements without introducing an analog filter for each PA. To demonstrate the effectiveness of the proposed technique, the simulations are analyzed for an array with 6-beam 64-chain configuration. Furthermore, experiments on a 2-beam 4-chain full-digital full-connected array are verified at the center frequency of 26 GHz with different modulated bandwidth scenarios. The experiment results indicate that the proposed method successfully achieves expected linearization performance for wideband multibeam array.

This paper presents a bandwidth-enhanced, low-profile dual-polarization (dual-pol) patch antenna array with a height of only 0.03λ₀ for glass-enclosed mobile platforms in 5G-enabled IoT applications at the millimeter-wave band. The bandwidth improvement and low-profile characteristic are achieved through a single-layer radiating patch fed by closely positioned lateral microstrip resonators, forming a multi-resonance structure that expands bandwidth while reducing the overall height by minimizing vertical feeding components. Dual-pol performance is accomplished via common-mode excitation of back-to-back C-shaped quarter-wavelength resonators on one side of the patch for one polarization, and differential-mode excitation of folded line-shaped resonators symmetrically placed on opposite sides for the orthogonal polarization, achieving extended bandwidth and high isolation. Building on this antenna element, a 1×4 dual-pol phased array is implemented for beam steering, fabricated using high-density interconnect (HDI) technology. Measurements reveal an operating bandwidth of 25.56–28.04 GHz (a fractional bandwidth of 9.5%) forx-pol and 24.42–28.49 GHz (15.6%) for y-pol. Beam scanning across ±45° shows a gain degradation of less than 3 dB, with cross-polarization levels remaining below -20 dB within the main lobe at each scan angle. This design is intended for integration within the camera region of a mobile terminal and has been optimized for operation in an under-glass environment. Performance tests conducted with a glass cover confirm the robustness of the design as an effective under-glass antenna for terminal applications.

Future sixth-generation (6G) low Earth orbit (LEO) satellite systems will utilize large-scale multi-beam phased arrays operating at millimeter-wave (mmWave) frequencies, with embedded power amplifiers (PAs) at each antenna element. However, the severe path loss drives PAs near saturation, and dynamic beamforming leads to nonuniform, time-varying PA conditions, jointly resulting in complex memory nonlinearities that degrade system performance. Such in-band distortions require mitigation by PA linearization, which remains highly constrained in LEO satellite systems. Therefore, accurate modeling and quantification of these nonlinearities are critical for realistic performance evaluation and to guide the development of effective linearization strategies. Current analytical methods focus on single-PA or memoryless-array models, without addressing the frequency-dependent statistical characteristics and spatially varying radiation patterns of nonlinear distortions in multi-beam phased arrays. In this paper, we develop statistical models for the PA output and the received signals in multi-beam phased arrays, explicitly decomposing the distortion structure and deriving closed-form expressions for each distortion component’s statistical properties. Furthermore, we analyze the spatial beam-pattern distortions and derive a closed-form expression for the signal-to-distortion-plus-interference-and-noise ratio (SDINR) under nonlinear distortion. Extensive simulations, conducted measurements, and over-the-air (OTA) experiments validate that the proposed model reduces optimal input back-off estimation error by 2 dB and improves SDINR prediction accuracy by approximately 3 dB. This research establishes a robust analytical foundation for future LEO satellite system design and linearization technology development.

In this work, the thresholds of the decomposed vector rotation (DVR) model for radio frequency (RF) power amplifiers (PAs) which based on canonical piecewise linear (CPWL) function, has been analyzed and optimized. The particle swarm optimization (PSO) algorithm is employed, and the thresholds of the DVR model is optimized to achieve the optimal performance. The basic theory and modeling procedure of the proposed technique are presented. Both Doherty PA (DPA) and sequential load modulated balanced amplifier (SLMBA) are used for experimental validation. Compared to the conventional Volterra-based model, the standard DVR model, the proposed PSO-based DVR (PSO-DVR) model present huge improvement. Compared with existing simultaneous perturbation stochastic approximation (SPSA) algorithm-based threshold optimization method, the optimization iteration number can be greatly reduced, which means the optimization efficiency is improved.

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 the era of 5G and beyond, the strategic utilization of both sub-6 GHz and millimeter-wave (mmWave) spectrums supports diverse communication services. Through smartphones, consumers can conveniently access a wide range of 5G/6G-enabled Internet of Things (IoT) scenarios anytime and anywhere. In this paper, mmWave and sub-6 GHz aperture-shared antenna and array are proposed for mobile terminals. For the mmWave antenna design, a slot radiating array is integrated into the metallic frame of a smartphone. This design incorporates a differential square-ring feeder and utilizes hybrid mode operation, enabling dual-polarized radiation capability across a wide operating frequency band. Importantly, this configuration requires only two metal layers with a 1.0-mm profile. Sharing the same frame, an inverted-F antenna (IFA) and a hybrid mode antenna with loop antenna and IFA operation are designed to work in sub-6 GHz bands. With the design principle of equal clearance, the sub-6 GHz antennas can perform well with the coexistence of the mmWave array. This approach is particularly applicable for sub-6 GHz antennas of different modes and frequencies. The proposed 1×4 mmWave phased array prototype demonstrates a -10 dB bandwidth of 23.3-30.8 GHz (covering the 5G n257/258 bands), a beam scanning range of ±40∘, and an in-band realized gain above 10.3 dBi. The sub-6 GHz antennas effectively cover 5G bands n1/2/3/7/18/28. By utilizing impedance tuning technique, the lower band can be further tuned to cover the bands n8/5.

In the realm of fifth-generation (5G)-enabled Internet of Things (IoT), the smartphone plays a pivotal role in providing users access to various IoT scenarios. With the emergence of millimeter-wave (mmWave) technology in 5G mobile terminals, it is feasible to realize an ultrabroadband, ultrahigh speed, and ultralow latency communication for advanced IoT applications. However, in a smartphone, the end-fire mmWave radiation is blocked by the metal frame. To solve this problem without altering the industrial design (ID) of the smartphone, we present a new mmWave beam-tilted phased array antenna with multiple hybrid modes operation. Our approach employs a physically oblique radiating aperture to achieve a tilted and frequency-insensitive radiation pattern, effectively addressing the interference from the smartphone platform while preserving the integrity of the ID. To expand the impedance bandwidth, monopole mode, magnetic dipole mode, and stepped patch mode are generated with an effective space utilization. For experimental validation, the proposed prototype is measured in a simplified mobile terminal. The$1\times 4$phased array achieves a −10 dB impedance bandwidth of 23.5–30.5 GHz, which covers the 5G n257 and n258 bands, with an in-band realized gain higher than 9.4 dBi. Furthermore, at 27.0 GHz, a wide 3-dB scanning range of 102.5°/72.0° is obtained for vertical/horizontal polarization, along with a peak gain of 9.4/11.0 dBi. The experimental results validate the proposed beam-tilted antenna solution, indicating that it can effectively address impedance mismatching, radiation distortion, low robustness, and other practical issues in 5G smartphones.

The novelty of this article is proposing an optimization strategy to design a high-efficiency load modulated balanced amplifier (LMBA) for integrated sensing and communication applications. Taking account of the operating characteristics, theoretical analysis reveals that different load modulation factors of the LMBA need to be realized in Mode I for communication applications, and in Mode II for sensing applications, respectively. To address this issue, the proposed strategy is used to optimize the LMBA, so as to achieve good performance for both modes. To verify the proposed strategy, an LMBA prototype operating from 1.55 to 2.55 GHz is designed with the use of three commercial gallium nitride (GaN) transistors. When tested in Mode I, the LMBA achieves a 9-dB back-off efficiency of 50.1%–68.7% and a saturated efficiency of 65.0%–79.6%. When excited by a 60-MHz 5G new radio signal with a 9-dB peak-to-average power ratio, the adjacent channel power ratio of the LMBA in Mode I is from -45 to -52.2 dBc after digital predistortion with the average efficiency of 50.0%–66.9% over the entire bandwidth. When the LMBA is measured in Mode II, it achieves a saturated output power of 43.7–45.4 dBm and a saturated efficiency of 55.3%–72.2% from 1.55 to 2.55 GHz.

In this work, the design of a load-modulated balanced power amplifier (LMBA), which is composed of a pair of classical balanced power amplifier (BA) and a signal control power amplifier (CA), based on using the X-parameter model is presented for the first time. A 10-W gallium nitride (GaN) packaged transistor is used for the power amplifier (PA) design. The extracted X-parameter model of the device under test (DUT) can accurately predict the nonlinear behavioral of the device, including both fundamental and harmonic characteristics, and determine the region of the Smith chart that leads to the optimal output power and drain efficiency (DE), with which the BA and CA are designed. In order to facilitate the application of the X-parameter for LMBA design, the X-parameter model of the classical BA pair is further extracted. Finally, an LMBA is fabricated and tested to verify the validity of the proposed design methodology. The measurements performed on the developed prototype show a saturation output power of up to 43.2 dBm in the frequency range of 1.3–1.6 GHz, with a saturation DE over 73% and an output power back-off (OBO) efficiency over 51% when it has more than 9-dB OBO. A single-carrier 20-MHz long-term evolution (LTE) signal is used to test the designed PA, and performance of the amplifier both with and without linearization are given.

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.