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This article presents a new broadband three-way series Doherty power amplifier (DPA) topology, which enables a broadband output power back-off (OBO) efficiency enhancement of up to 10 dB or higher. The proposed DPA topology achieves Doherty load modulation and three-way power combining through a transformer, which requires only a low coupling factor, thus facilitating its implementation in double-sided PCBs or monolithic microwave integrated circuit (MMIC) processes. The design equations for the proposed DPA topology are proposed and analyzed in detail. A proof-of-concept PA at the 2.1–2.8 GHz band using commercial GaN transistors was designed and fabricated to validate the proposed concept. Within the operating frequency band, it achieves a saturated output power ( P sat ) of 44.5–46.5 dBm with a peak drain efficiency (DE) of 60–72%, and 43–52% DE at 10 dB OBO. Moreover, under a 20 MHz long-term evolution (LTE)-modulated signal, the PA demonstrates a 36.8–37.5 dBm average output power ( P avg ) and 47–53% average drain efficiency ( DE avg ). Notably, the adjacent channel leakage ratio (ACLR) is as low as −35–−28.2 dBc without any digital predistortion (DPD). [ABSTRACT FROM AUTHOR]

In this paper, physical layer security is investigated, which is characterized by utilizing the physical layer characteristics to achieve secure transmissions without adopting encryption or decryption. In order to acquire the secrecy capacity, we propose to employ the nonlinear transmission, where the operating point of the power amplifier is set to be relatively high, so that the transmitted signal displays obvious nonlinear property. At the receiver side, the legitimate user can carry out the nonlinear reception scheme utilizing the predesigned training information, which is unavailable for the wiretap channel. Consequently, the eavesdropper could hardly decode the messages correctly from the received nonlinearly distorted signal, leading to an effective enhancement of secrecy capacity. To validate the secrecy performance of this approach, nonlinearity cancellation algorithm is employed at the confidential receiver, while OFDM and single carrier systems are exploited in the simulations. Numerical results show that the proposed nonlinear transmission method has the capability in achieving the secrecy capacity for physical layer security. [ABSTRACT FROM AUTHOR]

In this study, we present a high peak power Ho :YLF amplifier seeded by an electro-optically diodepumped Ho :GdVO4 laser operating at 2.05 μm. The diode-pumped Ho :GdVO4 laser, operating under a continuous-wave (CW) regime, achieved an output power of 7.1 W at an absorbed pump power of 28 W, resulting in a slope efficiency of 41.4%. At a repetition rate of 1 kHz, the laser delivered an average output power of 3.6 W with a pulse width of 4.3 ns. By utilizing a Ho :YLF crystal as the amplification medium, with a seed power of 3 W and an incident pump power of 22.5 W, the amplifier generates an average output power of 15.5 W with a pulse width of 4.5 ns. We calculate the maximum pulse energy and peak power to be 15.5 mJ and 3.4 MW, respectively. [ABSTRACT FROM AUTHOR]

A broadband Doherty power amplifier (DPA) always experiences an efficiency degradation between two efficiency peaks, especially at two side bands. In this study, the efficiency degradation was demonstrated to be caused caused by the in-phase power combining at the saturation power level. To solve this problem, current misalignment was introduced into the broadband DPA design. The carrier and peaking PA have different current phases when performing the power combination at the saturation power level. In this work, it was also demonstrated that the efficiency in the high-power region of a DPA can be improved by elaborately using misaligned current phases. A detailed analysis and the design procedure of a broadband DPA are presented in this paper. And a 1.5–2.45 GHz broadband DPA was implemented and measured. The fabricated DPA achieves a saturation output power of 42.7–44.9 dBm, a saturation drain efficiency (DE) of 62.7–74.1% and a gain of 10.2–13.9 dB over 1.5–2.45 GHz. Moreover, the fabricated DPA also achieves a 6 dB back-off DE of more than 49.1% in the frequency band of interest. [ABSTRACT FROM AUTHOR]

In this article, a 7–11.5 GHz 2‐W power amplifier (PA) based on cascode transistors is developed using 0.15‐µm GaAs pHEMT. This design facilitates impedance matching in the broadband range by using a cascode structure. A double‐cascode transistors structure is used as a unit cell to combine radio frequency voltage swings to achieve a broad bandwidth (BW). In addition, power synthesis techniques are used to achieve higher power output. Ultimately, based on the above two structures, a four‐way power‐synthesized PA is designed. The fabricated PA shows a peak power of 33.8 dBm at 9 GHz with a power‐added efficiency (PAE) of 43%. The output power is higher than 32 dBm at frequencies from 6 to 11.5 GHz with a PAE of more than 25%. The fractional 3‐dB output power BW is 80%. The chip area is 3.6 × 1.8 mm2, including the input and output test pads. [ABSTRACT FROM AUTHOR]

An efficient and compact, 20 kW solid-state power amplifier (SSA) at 325 MHz has been designed and developed in-house, using single stage combining. It comprises of 24 nos. of 1 kW power amplifier (PA) modules, a 24-way Wilkinson power combiner and divider, and other peripheral systems. The typical gain and conversion efficiency of the PA modules at 1.0 kW output is 21.7 dB and 66.6%, respectively. It is demonstrated that overall power gain and AC to RF efficiency of this SSA at 20 kW is 88.5 dB and 54.8%, respectively, which matches closely with the design estimates. The harmonic content in the RF output is < −40 dBc for all the harmonics. The results of the Monte Carlo simulation are also presented, showing lower bound on combining efficiency with a degree of confidence if magnitude and phase data for 24 inputs are randomly chosen from a normal distribution's pre-defined interval. The salient features of this SSA include power density of 12.7 kW/m3, AC to RF efficiency of 54.8% at 20 kW, and guaranteed output of 20 kW with one failed PA module and 18.1 kW under two failed PA modules condition. [ABSTRACT FROM AUTHOR]

This article presents a model that can automatically produce a power amplifier's (PA) design parameters, that is, transmission lines (TLs) dimension, from a dataset of user‐specified design goals like gain, efficiency, linearity, and scattering (S‐) parameters. Based on the applied boundary conditions, a synthetic dataset is generated with the best range of design parameters (W and L). This dataset is utilized for training the physics‐informed neural network (PINN) model with user‐specified design goals as input and design parameters as target to produce the optimum value of W and L as the resultant output. Furthermore, utilizing the obtained dimensions, design, simulation, fabrication, and measurement of a PA are performed to validate our proposed model. The results of large signal measurements of PA are drain efficiency (DE) of 26.9%, power added efficiency (PAE) of 24.7%, output power (Pout) of 30.98 dBm at an input power Pin$$ \left({P}_{in}\right) $$ of 19 dBm, and gain of 12.41 dB at an operating frequency of 1.625 GHz. It has been observed that the design parameters produced by the model have a significant agreement with the validated output. Also, the statistical error analysis is done by calculating the error metrics between the validated output and the actual output of the PA design. [ABSTRACT FROM AUTHOR]

Summary: This paper presents Doherty power amplifier (DPA) based on gallium nitride (GaN) technology, incorporating a parallel grounded network with series RC elements in front of the carrier and peaking amplifiers to enhance circuit stability. In comparison to the traditional series network with parallel RC structure, this configuration effectively reduces the sensitivity of the stability factor K to the capacitance value within the stability network. Consequently, it mitigates the impact on various performance indicators such as gain and drain efficiency, addressing the issue of measurement performance deviation caused by inaccurate capacitance models in the simulation files, which is particularly crucial for DPA. As a result, the circuit exhibits improved consistency in design and processing. With full band stability, the DPA achieves a saturation output power of approximately 29.8 dBm at 28 GHz, a saturation efficiency of 38.2%, and a 6‐dB back‐off efficiency of 29.6%. [ABSTRACT FROM AUTHOR]

Due to the limitation of high power amplifier's (HPA) physical structure, challenges such as nonlinearity and memory distortions which impact the transmitted signal in HPA system remain as an open research problem. As such, this paper introduces a simple and low complex Hammerstein model design as a digital predistorter (DPD) which can handle both of the mentioned challenges. This model first estimates the reverse error to deal with the nonlinearity effect. Subsequently, the DPD complexity is eliminated by removing the order of the memory polynomial. In order to reduce the memory effect resulting from HPA, the proposed model deploys traditional filter such as Finite Impulse Response to the acquired signal in the Hammerstein model. The simulation results show that the proposed DPD outperforms the current best practices for nonlinearity by 96 % from the ideal signal, and memory effect compensation by 95 % from the original signal position in space. Based on that, the proposed DPD can be utilized as conventional HPA for transmitting a standard signal with minimum risk of distortion, and achieving high signal to noise ratio against state-of-the-art models. [ABSTRACT FROM AUTHOR]

A design of a broadband Doherty power amplifier (DPA) using a novel harmonic control network (HCN) is presented. The DPA structure focused on manipulating harmonic components using this new HCN to enhance the bandwidth of operation and power efficiency. The proposed HCN combines a third harmonic suppression network (THSN) with the second harmonic impedance inverter circuit (SHIIC). In the design, the second harmonic component of the main transistor and the peaking transistor are short‐circuited by their associated SHIIC. Additionally, the carefully designed SHIIC and THSN circuit placed between the main and peaking transistors realise open circuit conditions at the third harmonic for both transistors at the saturation state and back‐off regions. Side by side with the aid of the properly designed post‐matching tuned network (PMTN), these harmonic loading conditions make both amplifiers to operate in continuous Class‐F modes with enhanced‐added efficiencies over wideband conditions. As a result, a succession of highly efficient DPA modes can be formed over a continuous frequency range in the full Doherty region, resulting in a reduced‐size enhanced power efficiency wideband DPA. For verification, a wideband DPA operating from 1.1 to 1.8 GHz was designed and implemented using the proposed topology. The measured drain efficiency of the implemented DPA at 6‐dB back‐off is 52.5%–67.5%, while the saturated power across the specified bandwidth is 43–43.7 dBm. The fabricated DPA exhibits an average efficiency of 48.7%–59.4%, when supplied by a 40‐MHz long‐term evolution (LTE) signal with a 7.5‐dB peak‐to‐average power ratio (PAPR). Performing digital pre‐distortion (DPD) improves the adjacent channel power ratio (ACLR) from −25.8 dBc to −47.6 dBc. [ABSTRACT FROM AUTHOR]

In this study, we designed a wideband CMOS power amplifier to support multi-band and multi-standard wireless communications. First, an input matching technique through LC network and a wideband design technique using a low Q-factor transformer were proposed. In addition, a design technique was proposed to improve output matching using RC feedback. To verify the feasibility of the proposed design methodology for wideband CMOS power amplifiers, the designed power amplifier was fabricated using a 180 nm RFCMOS process. The size including all of the matching network and test pads was 1.38 × 0.90 mm2. In addition, the effectiveness of the proposed power amplifier was verified through the measured results using modulated signals of WCDMA, LTE, and 802.11n WLAN. [ABSTRACT FROM AUTHOR]

Next-generation wireless systems require increased spectral and energy efficiency in terminals. This can only be achieved if the nonlinear characteristics of the radio front-end, primarily the power amplifier (PA), are known and considered while designing algorithms or optimizing radio links. PA datasheets contain limited information, and wideband PA measurements typically require advanced equipment and software. This paper proposes a measurement and signal processing framework that enables the acquisition of nonlinear PA characteristics using generic complex sample transmitters and receivers, e.g., software-defined radio (SDR). This paper also proposes a multistage signal calibration and synchronization procedure that allows obtaining nonlinear PA characteristics that are non-distorted by other phenomena. The correctness and usefulness of the proposed framework are demonstrated by measuring three PAs, each under varying supply voltage and carrier frequency. At the same time, the high variability of the obtained nonlinear characteristic justifies the need for PA measurements to obtain awareness of nonlinear characteristics. [ABSTRACT FROM AUTHOR]

In this paper, a novel wideband power amplifier (PA) operating in the 2–6 GHz frequency range is presented. The proposed PA design utilizes a combination technique consisting of a distributed equalization technique, multiplexing the power supply network and matching network technique, an LR dissipative structure, and an RC stability network technique to achieve significant bandwidth while maintaining superior gain flatness, high efficiency, high gain, and compact size. For verification, a three-stage PA using the combination technique is designed and implemented in a 0.25 μm GaN high-electron-mobility transistor (HEMT) process. The fabricated prototype demonstrates a saturated output power of 4 W, a power gain of 21 dB, a gain flatness of ±0.6 dB, a power-added efficiency of 39–46%, and a fractional bandwidth of 100% under the operating conditions of drain voltage 28 V (continuous wave) and gate voltage −2.6 V. Moreover, the chip occupies a compact size of only 2.51 mm × 1.97 mm. [ABSTRACT FROM AUTHOR]

The impact of embedded microfluidic cooling on the performance of Ku-band gallium nitride (GaN) microwave monolithic integrated circuit (MMIC) power amplifiers (PAs) has been studied in this work. The research demonstrates that embedded cooling can substantially lower junction temperatures, mitigate the self-heating effect, and thereby improve the electrical performance of GaN MMIC PAs. Using merely 10.4 mW of pumping power (Ppump), the technology reduces the maximum junction temperature (Tj,max) from 216.7 to 147.8 °C. Furthermore, the system enhances the saturation current by 13.8%, increases output power (Pout) and gain (Gain) by 1.8 dB, elevates the power added efficiency (PAE) by 5.9%, and improves the heat flux of last gate (Qgate) to 37.3 kW/mm2 and the heat flux of MMIC (QMMIC) over 2.6 W/mm2, while reducing the thermal resistance (Rj-c) from 2.13 to 1.26 °C/W. Additionally, there is a notable improvement of the small signal gain (S21) by 2.5 dB. Therefore, the achievements in this work indicate that embedded cooling offers a powerful technique to suppress the thermal effects on GaN MMIC PAs, consequently improving their electrical performance. [ABSTRACT FROM AUTHOR]

In this study, we report on the direct-current (DC) and frequency characteristics of split-gate heterostructure field-effect transistors (HFETs) with different split-gate lengths. The split-gate HFET contains two distinct operating parts, the large and the small transconductance parts. The split-gate HFET has a current cutoff frequency ( f T ) of 814 MHz and a maximum oscillation frequency ( f max ) of 18.8 GHz in the large transconductance part. Meanwhile, in the small transconductance part, there is a higher unilateral power gain of f max = 2 7. 7 GHz. Also, the split-gate HFET exhibits a voltage gain greater than 1 (0 dB) at both DC and frequencies. Additionally, compared to the large transconductance part, the small transconductance part of the split-gate HFET presents a 53.5% reduction in DC power consumption and a larger input signal voltage range. Split-gate HFETs can be used as conventional power amplifiers in the large transconductance part and are also suitable as low-power voltage amplifiers in the small transconductance part. [ABSTRACT FROM AUTHOR]

This paper presents a groundbreaking Ku-band 20W RF front-end power amplifier (PA), designed to address numerous challenges encountered by satellite communication systems, including those pertaining to stability, linearity, cost, and size. The manuscript commences with an exhaustive discussion of system design and operational principles, emphasizing the intricacies of low-noise amplification, and incorporating key considerations such as noise factors, stability analysis, gain, and gain flatness. Subsequently, an in-depth study is conducted on various components of the RF chain, including the pre-amplification module, driver-amplification module, and final-stage amplification module. The holistic design extends to the inclusion of the display and control unit, featuring the power-control module, monitoring module, and overall layout design of the PA. It is meticulously tailored to meet the specific demands of satellite communication. Following this, a thorough exploration of electromagnetic simulation and measurement results ensues, providing validation for the precision and reliability of the proposed design. Finally, the feasibility of that design is substantiated through systematic system design, prototype production, and exhaustive experimental testing. It is noteworthy that, in the space-simulation environmental test, emphasis is placed on the excellent performance of the Star Ku-band PA within the 13.75GHz to 14.5GHz frequency range. Detailed power scan measurements reveal a P1dB of 43dBm, maintaining output power flatness < ± 0.5dBm across the entire frequency and temperature spectrum. Third-order intermodulation scan measurements indicate a third-order intermodulation of ≤ -23dBc. Detailed results of power monitoring demonstrate a range from +18dBm to +54dBm. Scans of spurious suppression and harmonic suppression, meanwhile, show that the PA evinces spurious suppression ≤ -65dBc and harmonic suppression ≤ -60dBc. Rigorous phase-scan measurements exhibit a phase-shift adjustment range of 0° to 360°, with a step of 5.625°, and a phase-shift accuracy of 0.5dB. Detailed data from gain-scan measurements show a gain-adjustment range of 0dB to 30dB, with a gain flatness of ± 0.5dB. Attenuation error is ≤ 1%. These test parameters perfectly align with the practical application requirements of the technical specifications. When compared to existing Ku-band PAs, our design reflects a deeper consideration of specific requirements in satellite communication, ensuring its outstanding performance and uniqueness. This PA features good stability, high linearity, low cost, and compact modularity, ensuring continuous and stable power output. These features position the proposed system as a leader within the market. Successful orbital deployment not only validates its operational stability; it also makes a significant contribution to the advancement of China's satellite PA technology, generating positive socio-economic benefits. [ABSTRACT FROM AUTHOR]

This article presents a resistive‐reactive Class‐X power amplifier (PA) with bandwidth beyond one octave. By introducing resistive component into the second‐harmonic load of Class‐X power amplifier, the impedance design space is expanded. The basic theory of extended Class‐X PA is deduced, including impedance calculation, high‐efficiency design consideration and targeted impedance trace design. An impedance overlapping region between fundamental and second‐harmonic impedances with high drain efficiency is obtained, paving the way for bandwidth enhancement. For validation, the Class‐X and extended Class‐X theory are employed to design a broadband PA with bandwidth of 0.6–2.6 GHz (125%), drain efficiency of 57%–70%, and gain of 10.2–13.2 dB. [ABSTRACT FROM AUTHOR]

Terahertz (THz) bands are considered to have various anticipated applications. Output power is an important factor determining the operating distance of THz systems, but it is very challenging to achieve high output power under current solid‐state terahertz circuit technology. The paper first presents a four‐way G‐band radial combiner, which features high passive efficiency of 88% and compact size. Moreover, based on this radial combiner and in‐house fabricated gallium nitride chips, a solid‐state power amplifier prototype is further demonstrated. Measured results show that, the average saturated output power is 21.7 dBm across the 180–240 GHz band with a typical output power of 23.2 dBm at 189 GHz. [ABSTRACT FROM AUTHOR]

One high efficiency second harmonic tuned (2HT) power amplifier (PA) with a compact multi‐harmonic tuning network is presented. The proposed design method can drive the third harmonic impedance to short‐circuit condition to achieve an ideal 2HT PA operation. Then the second harmonic impedance is controlled to proper position to improve the PA efficiency. Meanwhile, the fundamental impedance is also transferred to 50 Ω load by making the most of this tuning network. Consequently, the proposed output network can be designed to a compact size and is suitable for high frequency PA applications. For demonstration, a PA using Cree CGH40010 GaN high‐electron‐mobility transistor is designed and fabricated at 3.5 GHz. The measured results show that the PA achieves peak power added efficiency of 72.8%, output power of 41.3 dBm and drain efficiency of 80.2% at 3.3 GHz. [ABSTRACT FROM AUTHOR]

In magnetic particle imaging, a field-free region is maneuvered throughout the field of view using a time-varying magnetic field known as the drive-field. Human-sized systems operate the drive-field in the kHz range and generate it by utilizing strong currents that can rise to the kA range within a coil called the drive field generator. Matching and tuning between a power amplifier, a band-pass filter, and the drive-field generator is required. Here, for reasons of safety in future human scanners, a symmetrical topology and a transformer called an inductive coupling network are used. Our primary objectives are to achieve floating potentials to ensure patient safety while attaining high linearity and high gain for the resonant transformer. We present a novel systematic approach to the design of a loss-optimized resonant toroid with a D-shaped cross section, employing segmentation to adjust the inductance-to-resistance ratio while maintaining a constant quality factor. Simultaneously, we derive a specific matching condition for a symmetric transmit–receive circuit for magnetic particle imaging. The chosen setup filters the fundamental frequency and allows simultaneous signal transmission and reception. In addition, the decoupling of multiple drive field channels is discussed, and the primary side of the transformer is evaluated for maximum coupling and minimum stray field. Two prototypes were constructed, measured, decoupled, and compared to the derived theory and method-of-moment based simulations. [ABSTRACT FROM AUTHOR]

Power amplifiers (PA) are used to boost the power of signals. Recently, harmonically tuned power amplifiers (HTPA) offer high efficiency and wider bandwidth than conventional PA. HTPA achieves by shaping waveforms using varying drain terminal impedance conditions (open and short-circuited etc.), but this impedance creates reflected waves at the drain. Existing HTPA methods lack a foundation in Electromagnetic Theory (EM), leading them to miss reflected waves. As a result, the existing equations show problems Type I: generate unwanted and non-required higher-order harmonics (n > 3); and Type II: they cannot link with simulated/measured results properly. This paper proposes an alternative approach by applying EM theory to develop a general HTPA equation. This equation works for any HTPA class and overcomes problems (Type I & II). To validate the proposed theory and equation, continuous mode Class F PA is designed and fabricated. Theoretical, simulation and experimental results all showed good agreement. [ABSTRACT FROM AUTHOR]

The practical implementation of massive multi-user multi-input–multi-output (MU-MIMO) downlink communication systems power amplifiers that are energy efficient; otherwise, the power consumption of the base station (BS) will be prohibitive. Constant envelope (CE) precoding is gaining increasing interest for its capability to utilize low-cost, high-efficiency nonlinear radio frequency amplifiers. Our work focuses on the topic of CE precoding in massive MU-MIMO systems and presents an efficient CE precoding algorithm. This algorithm uses an alternating minimization (AltMin) framework to optimize the CE precoded signal and precoding factor, aiming to minimize the difference between the received signal and the transmit symbol. For the optimization of the CE precoded signal, we provide a powerful approach that integrates the majorization-minimization (MM) method and the fast iterative shrinkage-thresholding (FISTA) method. This algorithm combines the characteristics of the massive MU-MIMO channel with the second-order Taylor expansion to construct the surrogate function in the MM method, in which minimizing this surrogate function is the worst-case of the system. Specifically, we expand the suggested CE precoding algorithm to involve the discrete constant envelope (DCE) precoding case. In addition, we thoroughly examine the exact property, convergence, and computational complexity of the proposed algorithm. Simulation results demonstrate that the proposed CE precoding algorithm can achievean uncoded biterror rate (BER) performance gain of roughly 1 dB compared to the existing CE precoding algorithm and has an acceptable computational complexity. This performance advantage also exists when it comes to DCE precoding. [ABSTRACT FROM AUTHOR]

This study proposes a novel, conditionally applied neural network technique to reduce the overall peak‐to‐average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) system while maintaining an acceptable bit error rate (BER) level. The main purpose of the proposed scheme is to adjust only those subcarriers whose peaks exceed a given threshold. In this respect, the developed C‐ANN algorithm suppresses only the peaks of the targeted subcarriers by slightly shifting the locations of their corresponding frequency samples without affecting their phase orientations. In turn, this achieves a reasonable system performance by sustaining a tolerable BER. For practical reasons and to cover a wide range of application scenarios, the threshold for the subcarrier peaks was chosen to be proportional to the saturation level of the nonlinear power amplifier used to pass the generated OFDM blocks. Consequently, the optimal values of the factor controlling the peak threshold were obtained that satisfy both reasonable PAPR reduction and acceptable BER levels. Furthermore, the proposed system does not require a recovery process at the receiver, thus making the computational process less complex. The simulation results show that the proposed system model performed satisfactorily, attaining both low PAPR and BER for specific application settings using comparatively fewer computations. [ABSTRACT FROM AUTHOR]

Multi-band transmission is one of the key practical solutions to cope with the continuously growing demand on the capacity of optical communication networks without changing the huge existing fiber base. However, ultra-broadband communication requires the development of novel power efficient optical amplifiers operating beyond C- and L-bands, and this is a major research and technical challenge comparable to the introduction of the seminal erbium-doped fiber amplifiers that dramatically changed the optical communication sector. There are several types of optical fibers operating beyond C- and L-bands that can be used for the development of such amplifiers, specifically the fibers doped with neodymium, praseodymium, thulium, and bismuth. However, among these, Bi-doped fibers are of special interest as the most promising amplification medium because, unlike the others, different Bi-associated active centers allow amplification in an enormous band of overall width of 700 nm (1100–1800 nm). Such spectral coverage can be obtained by using different host materials, such as aluminosilicate, phosphosilicate, silica, and germanosilicate glasses. Here, we report a novel Bi-doped fiber amplifier with record characteristics for E-band amplification, including the highest power conversion efficiency among telecom-compatible E-band amplifiers reported to date. This bismuth-doped fiber amplifier (BDFA) features a maximum gain of 39.8 dB and a minimal noise figure of 4.6 dB enabled by 173 m Bi-doped fiber length. The maximum achieved power conversion efficiency of 38% is higher than that of L-band Er-doped fiber amplifiers. This performance demonstrates the high potential of BDFA for becoming the amplifier of choice in modern multi-band optical communication networks. [ABSTRACT FROM AUTHOR]

In this paper, we develop a kW-level high-repetition-rate nanosecond master oscillator power amplifier (MOPA) laser system, employing a structure of fiber, Nd:YVO4, and Nd:YAG hybrid amplification. A tunable fiber seed source is used for adjustable pulse repetition frequency and pulse width. The Nd:YVO4 pre-amplifier, which is dual-end-pumped, achieves high gain while maintaining good beam quality, and the high-power side-pumped Nd:YAG slab main-amplifier enables efficient power amplification. The repetition rate of the output laser can be adjusted within the range of 1~20 kHz, and the pulse width can be tuned within the range of 10~300 ns. The seed output is 6 mW at a repetition frequency of 20 kHz; we achieve an average output power of 1240 W with a total power extraction efficiency of 39.1% and single-pulse energy of 62 mJ at a pulse width of 301 ns. This parameter-controllable high-power laser holds promise for applications in the laser cleaning of complex surface contaminants. [ABSTRACT FROM AUTHOR]

Waste heat dissipation from spacecraft subsystems is crucial due to spatial limitations (no convective heat transfer, limited electrical power, lightweight, and high reliability). Radiators are often responsible for collecting and dissipating this waste heat into cold space. Panel radiators are widely used in various satellites, including scientific, communication, and remote sensing satellites. In scientific satellites, panel radiators are used to dissipate heat generated by scientific instruments such as cameras and spectrometers. In communication satellites, panel radiators are used to dissipate heat generated by power amplifiers. In remote sensing satellites, panel radiators are used to dissipate heat generated by sensors and processors. High efficiency, light weight, and high reliability are the advantages of using this equipment. The main challenge in using it is to provide sufficient heat dissipation area and uniformity of the surface temperature when radiating waste heat to the cold environment (space). The use of heat pipes in the panel radiator structure provides this uniformity. A heat pipe radiator consists of a sandwich panel with an embedded network of heat pipes. Increasing the number of heat pipes reduces the temperature gradient across the radiator surface but increases the radiator weight. Due to the importance of equipment lightness in space systems, optimization of the number of pipes and their geometric arrangement in the radiator should be such that maximum temperature uniformity on the surface and minimum radiator weight are achieved. The objective of this research is to optimize the performance of a radiator (maximum temperature uniformity on the surface) to achieve minimum weight while considering the weight and size constraints imposed by the system designer as requirements. Initially, a mathematical model is developed and solved numerically, and the effect of design parameters on the performance of a panel radiator, including face and core thickness, spacing between heat pipes, mass, and surface area, is comprehensively investigated. Based on the simulation results, considering the weight limitations and existing face and core thicknesses, the maximum allowable spacing between heat pipes is calculated to achieve maximum efficiency of the panel radiator. A network of heat pipes with this characteristic was produced and used in the panel sandwich. The results obtained from testing the manufactured panel radiator were compared with the design efficiency to validate the model. Based on the experimental results, an efficiency of 89% was obtained at a root temperature of 39°C. The error of this efficiency with the efficiency calculated from the theory is about 3%.Waste heat dissipation from spacecraft subsystems is crucial due to spatial limitations (no convective heat transfer, limited electrical power, lightweight, and high reliability). Radiators are often responsible for collecting and dissipating this waste heat into cold space. Panel radiators are widely used in various satellites, including scientific, communication, and remote sensing satellites. In scientific satellites, panel radiators are used to dissipate heat generated by scientific instruments such as cameras and spectrometers. In communication satellites, panel radiators are used to dissipate heat generated by power amplifiers. In remote sensing satellites, panel radiators are used to dissipate heat generated by sensors and processors. High efficiency, light weight, and high reliability are the advantages of using this equipment. The main challenge in using it is to provide sufficient heat dissipation area and uniformity of the surface temperature when radiating waste heat to the cold environment (space). The use of heat pipes in the panel radiator structure provides this uniformity. A heat pipe radiator consists of a sandwich panel with an embedded network of heat pipes. Increasing the number of heat pipes reduces the temperature gradient across the radiator surface but increases the radiator weight. Due to the importance of equipment lightness in space systems, optimization of the number of pipes and their geometric arrangement in the radiator should be such that maximum temperature uniformity on the surface and minimum radiator weight are achieved. The objective of this research is to optimize the performance of a radiator (maximum temperature uniformity on the surface) to achieve minimum weight while considering the weight and size constraints imposed by the system designer as requirements. Initially, a mathematical model is developed and solved numerically, and the effect of design parameters on the performance of a panel radiator, including face and core thickness, spacing between heat pipes, mass, and surface area, is comprehensively investigated. Based on the simulation results, considering the weight limitations and existing face and core thicknesses, the maximum allowable spacing between heat pipes is calculated to achieve maximum efficiency of the panel radiator. A network of heat pipes with this characteristic was produced and used in the panel sandwich. The results obtained from testing the manufactured panel radiator were compared with the design efficiency to validate the model. Based on the experimental results, an efficiency of 89% was obtained at a root temperature of 39°C. The error of this efficiency with the efficiency calculated from the theory is about 3%. [ABSTRACT FROM AUTHOR]

A nonlinear capacitance compensation technique is presented in this paper to enhance the linearity of a power amplifier (PA) in the GaN process. The method involves placing an MSM varactor device alongside the GaN HEMT device, which works as the amplifying unit such that the overall capacitance observed at the amplifier input is constant, thus improving linearity. This approach is a reliable and straightforward way to improve PA linearity in the GaN process. The proof-of-concept prototype in this study involves the fabrication of a PA device using a standard GaN HEMT process, which successfully integrates the proposed compensation technique and demonstrates excellent compatibility with existing processes. The prototype has a saturation output power of 18 dBm, a peak power-added efficiency of 51.8%, and a small signal gain of 15.5 dB at 1 GHz. The measured AM–PM distortion at the 5 dB compression point is reduced by more than 50% compared to that of an uncompensated device. Furthermore, the results of third-order intermodulation distortion demonstrate the effectiveness of the linearity enhancement concept, with values improved by more than 5 dB in the linear region compared to those of the uncompensated device. All of the results demonstrate the potential utility of this design approach for wireless communication applications. [ABSTRACT FROM AUTHOR]

This paper presents an ultra-wideband transformer feedback (TFB) monolithic microwave integrated circuit (MMIC) power amplifier (PA) developed using a 0.25 μm gallium nitride (GaN) process. To broaden the bandwidth, a drain-to-gate TFB technique is employed in this PA design, achieving a 117% relative −3 dB bandwidth, extending from 5.4 GHz to 20.3 GHz. At a 28 V supply, the designed PA circuit achieves an output power of 25.5 dBm and a 14 dB small-signal gain in the frequency range of 6 to 19 GHz. Within the 6 to 19 GHz frequency range, the small-signal gain exhibits a flatness of less than 0.78 dB. The PA chip occupies an area of 1.571 mm2. This work is the first to design a power amplifier with on-chip transformer feedback in a compound semiconductor MMIC process, and it enables the use of the widest bandwidth power amplifier on-chip transformer matching network. [ABSTRACT FROM AUTHOR]

When it comes to the radio frequency (RF) frontend, power amplifier (PA) is one of the most important functional blocks for dependable wireless transmission. In order to provide the necessary output power, PAs boost and amplify the incoming signal, to ensure that the transmitter's signal reaches the receiver at the necessary distance. The PAs have not yet managed to find place within the transceiver circuit due to its bulky nature. Although rigorous efforts have been made to improve the linearity and efficiency of the PAs, it has come at the cost of increase in chip area. This paper focusses on design of an RFPA in an 18nm FinFET advanced node technology that is adaptable to the Sub-6 GHz frequency band of 5G communication standard so as to provide maximum output power at the operating frequency of 3.5GHz. The single stage PA, thus designed and simulated on Cadence Virtuoso provides a gain of 27.71 dB at a supply voltage of 1V. The bandwidth is 208 MHz, power gain is 25dB and the output power is 6.335 dBm. The simple design with a single transistor paves way for a considerable decrease in the chip area, thus making it possible to be placed within the transceiver chip. [ABSTRACT FROM AUTHOR]

This paper presents the design and measurements of a 215-252 GHz 40 nm bulk CMOS frequency doubler with a 6.8 dBm deliverable peak output power and a conversion gain of 11.8 dB. The designed chip is composed of a 28.5 dB gain 6-stages 110 GHz power amplifier, an optimized push-push doubler biased in class-C configuration, and an output impedance matching network. A numerical method had been applied here for designing each implemented matching network achieving the optimum matching while maintaining the minimum insertion loss as well. The presented design shows the highest output power among the other sub-THz-designed CMOS counterparts. The design occupies an area of 0.795 mm2 and shows a total DC power dissipation of 262 mW and DC-RF efficiency of 1.87%. [ABSTRACT FROM AUTHOR]

In this paper, a high-efficiency class-F power amplifier with a harmonic control circuit is proposed. The harmonic control circuit is realised by loading microstrip branch lines to achieve a short-circuit state for the second harmonic. The double spiral defected ground units are loaded on the ground of the microstrip line of the drain bias circuit to produce a low-pass filtering and stopband suppression effect outside the passband, so as to suppress the third harmonic. Meanwhile, it would provide an open-circuit state for the third harmonic, and finally meet the harmonic impedance tuning demands of class-F power amplifier. Through theoretical analysis and simulation, a high-efficiency class-F power amplifier operating at 2.5 GHz ~2.7 GHz is designed. The measured results show that in the working frequency band, the drain efficiency is 66.3%~71.1%, the output power is 40.9 dBm ~42.1 dBm and the gain is 10.9 dB ~11.8 dB. [ABSTRACT FROM AUTHOR]

A 2–26.5GHz broadband amplifier monolithic microwave integrated circuit (MMIC) based on the 0.15 μm GaN high electron mobility transistor process has been developed. The broadband amplifier adopts a two‐stage distributed amplifier cascade structure, which improves the gain of the broadband amplifier. Further, the capacitive coupling is used to improve the gain bandwidth product of the power amplifier. To improve the output return loss of the wideband amplifier, a tuning stub is introduced at the output of the circuit. The on‐wafer measurement results show that the amplifier has a gain greater than 18 dB, gain flatness less than ±1.4 dB, and saturated output power >35 dBm with a >13% power added efficiency in the whole band. [ABSTRACT FROM AUTHOR]

Parametric amplifiers have become a workhorse in superconducting quantum computing; however, research and development of these devices has been hampered by inconsistent and, sometimes, misleading noise performance characterization methodologies. The concepts behind noise characterization are deceptively simple, and there are many places where one can make mistakes, either in measurement or in interpretation and analysis. In this article, we cover the basics of noise performance characterization and the special problems it presents in parametric amplifiers with limited power handling capability. We illustrate the issues with three specific examples: a high-electron mobility transistor amplifier, a Josephson traveling-wave parametric amplifier, and a Josephson parametric amplifier. We emphasize the use of a 50-Ω shot noise tunnel junction (SNTJ) as a broadband noise source, demonstrating its utility for cryogenic amplifier amplifications. These practical examples highlight the role of loss as well as the additional parametric amplifier "idler" input mode. [ABSTRACT FROM AUTHOR]

The power amplifiers (PAs) will embody the nonlinear distortion if they work at saturation so as to increase efficiency. The neural network (NN)‐based digital predistortion (DPD) is widely applied for the linearization of the PA in wireless communication. However, the current NN‐based DPD schemes only focus on designing the NN hidden layer and ignore improving the NN input layer, which loses the degree of freedom to fit the DPD. Therefore, this paper first proposes the generalized memory polynomial (GMP) input NN structure. The training data of GMP‐NN outputs are obtained by iterative learning control. The experimental results show that the GMP‐NN presents a great advantage in performance compared with the widely used GMP model and recurrent NN (RNN) model. From the testing data, it is observed that the minimum mean square error (MMSE) of the GMP‐NN is 4 dB lower than the conventional GMP model and is nearly 8 dB lower than the RNN model. The proposed GMP‐NN model is also verified in the DPD application, which shows 2.61 dB improvement in comparison with the GMP DPD model. [ABSTRACT FROM AUTHOR]

Support vector machine (SVR) has been introduced into the modeling of S‐parameters in radio‐frequency (RF) power amplifiers (PA). The modeling accuracy and speed of SVR are primarily affected by the penalty parameter c and the kernel function coefficient γ. Using the traditional grid search technique to determine these two parameters is time‐consuming and labor‐intensive, and ensuring the model's accuracy is not easy. This article proposes an S‐parameters modeling method based on PSO‐GA‐SVR to improve the SVR's modeling accuracy and speed. The model mainly focuses on particle swarm optimization (PSO) and combines selection, crossover, and mutation operations in genetic algorithms (GA). The fitness values are arranged from small to large in each iteration process, and the first 1/3 are selected for crossover and mutation. Then, the resulting new particle swarms are introduced into the original particle swarm population for searching. On the one hand, PSO‐GA extends the population size and reduces the possibility of falling into local optimization. On the other hand, due to population size expansion, the number of iteration rounds is reduced, and the modeling speed is also increased. The experimental results show that compared to SVR, GA‐SVR, and PSO‐SVR, the proposed PSO‐GA‐SVR can improve the modeling accuracy by more than one magnitude or more while also increasing modeling speed by one magnitude or more. Furthermore, compared with the classical machine learning algorithms such as gradient boosting, random forest, and gcForset, the proposed PSO‐GA‐SVR improves the modeling accuracy by one order of magnitude and the modeling speed by two orders of magnitude more than gradient boosting, random forest, and improves the modeling speed by one order of magnitude more than gcForset. [ABSTRACT FROM AUTHOR]

In this paper, an automatic multi‐objective particle swarm optimization (AMOPSO) method is developed for the design of Doherty power amplifiers (DPAs). In comparison to the well‐known built‐in optimizer available in commercial simulators, the proposed method not only reduces the optimization time, but also provides superior power added efficiency (PAE) for the final power amplifier. According to the reported measurements, the output PAE of the fabricated DPA exceeds 50% at 6 dB backoff, the saturated PAE is more than 61%, and the saturated output power (Pout) is over 43 dBm in the target frequency range of 1.9–2.1 GHz. As compared with existing optimization methods, the proposed method allows reducing optimization time by more than 37%. [ABSTRACT FROM AUTHOR]

This paper proposes a ± 9.4 ps ultra‐small group delay (GD) variation of fully integrated 65 nm complementary metal oxide semiconductor (CMOS) power amplifier (PA) over 6.5–17 GHz broadband for wireless application. The proposed CMOS PA is realised by using broadband stage, RLC inter‐stage and power stage topologies. The non‐dominated sorting genetic algorithm (NSGA‐II) is employed for PA parameter optimisation to ensure a small GD variation of ±9.4 ps over broadband with an excellent small signal gain flatness of 23.65 ± 1.85 for 6.5–17 GHz. The small GD variation of ±9.4 ps and ± 11.05 ps are attained under two cases of DC supply voltages of 2.4/1.2 V and 1.2/1.2 V, respectively. To the best of author's knowledge, the achieved GD variations are lowest among all CMOS PAs as reported so far. In addition, an analytical modelling of GD is derived to validating the minimum GD variation using zero‐pole compensation. With supply voltages of 2.4/1.2 V at 6.5 GHz, the large signal power gain, Psat and OP1dB are 26 dB, 19.3 dBm and 17.94 dBm, respectively, while peak power added efficiency (PAE) is 38.196%. At reduced supply voltages of 1.2/1.2 V, the PA achieves maximum power gain of 17.7 dB and peak PAE of 35% at 6.5 GHz. The CMOS PA occupies an area of 0.206 mm2. [ABSTRACT FROM AUTHOR]

XGBoost is the optimization of gradient boosting with the best overall performance among machine learning algorithms. By introducing a regularization term into the loss function of gradient boosting, XGBoost can effectively limit the complexity of the model, improve the generalization ability, and solve the overfitting problem. In this paper, XGBoost is first introduced into modeling radio‐frequency (RF) power amplifiers (PA) under different temperatures. Furthermore, the modeling effect of XGBoost is mainly dependent on hyperparameters. As traditional grid search is time‐consuming and labor‐intensive, this paper combines particle swarm optimization (PSO) with XGBoost for searching hyperparameters. The experimental results show that XGBoost can effectively suppress the overfitting problem in gradient boosting while modeling RF PAs in different ambient temperatures. In addition, compared to classic machine learning algorithms, including support vector regression (SVR), gradient boosting, and XGBoost, the proposed PSO‐XGBoost can increase the modeling accuracy by one order of magnitude or more while also increasing the modeling speed by more than one magnitude or more. The PSO‐XGBoost model proposed in this paper can be introduced into modeling other microwave/RF devices and circuits to improve modeling accuracy and reduce modeling time. [ABSTRACT FROM AUTHOR]

Using a large number of power amplifiers brings serious nonlinear distortion to 5G communication systems, which becomes a challenging problem for conventional digital predistortion (DPD) to linearize signals. To address this challenge, we propose a digitally assisted nonlinearity suppression architecture for applications in multiple antenna arrays. In this architecture, we use an auxiliary array to generate a nonlinear cancelation signal to cancel with the main beam at the receiving end. We explore a two‐step method to model the nonlinear signal and combine neural network to complete the modeling. In addition, we introduce a novel method for estimating and tracking the channel to update the model coefficients. To verify the proposed methods, we design a scene and compare the performance of our architecture with that of conventional DPD. Our experiments demonstrate that our proposed methods can significantly enhance the adjacent channel power leakage ratio performance by 12 dB while also optimizing in‐band distortion. Moreover, our architecture outperforms conventional DPD approaches even with enhanced distortion. [ABSTRACT FROM AUTHOR]

High frequency (HF) transmitter implemented with the multioctave broadband power amplifier (PA) is always faced with the problem of interfering harmonics because of the nonlinearity of the PA. With the harmonic‐cancelation digital predistortion (HC‐DPD) scheme, the harmonics at lower frequencies can be canceled by the injected components and the harmonics at higher frequencies can be filtered out using a low‐pass filter (LPF). However, the HC‐DPD scheme brings the problem of unwanted spurs while lowering the requirements for sampling rate. In this article, a time‐delay neural network (TDNN) model is used to replace the conventional memory polynomial (MP) model in the forward modeling. Theoretical derivation and simulation results validate the effectiveness of the TDNN model in harmonic cancelation and spur suppression. Further, a frequency‐agile neural network (FANN) model is proposed based on the TDNN model. By adding the carrier frequency to the inputs of the network, the trained model can apply to all the trained carrier frequencies and is more friendly to the frequency‐hopping scenarios. Experiments were carried out on a 2–30 MHz HF transmitter testbench. Measurement results show that the harmonic‐to‐fundamental power ratio, the adjacent channel power ratio (ACPR), and the error vector magnitude (EVM) performances were all improved by more than 20 dB. Compared with the MP model, the unwanted spurs can be suppressed by up to 22 dB. In addition, the number of total model coefficients of the proposed FANN model is only 22% of that of the TDNN model under the frequency‐hopping scenario. [ABSTRACT FROM AUTHOR]

This article examines the effects of Bayesian optimization (BO) with different covariance functions on the optimization of a radio frequency power amplifier (RFPA). An initial PA is designed based on a Chebyshev low‐pass topology using a 10 W Gallium Nitride (GaN) transistor. The objective function is established in a novel manner. The performance of the initially designed PA was optimized by using various BO algorithms, including two different acquisition functions and five different covariance functions. Both simulation and measurement results indicate that the kernel squared exponential (KSE) and Matérn32 covariance functions provide the best option for optimizing PA by BO. A broadband power amplifier (PA) operating at a frequency range from 2.5 GHz to 3.5 GHz has been developed with an output power (Pout) greater than 40.8 dBm and a power‐added efficiency (PAE) greater than 65%. [ABSTRACT FROM AUTHOR]

In the manufacturing process of power amplifier (PA), various defects on the circuit surface will seriously affect the circuit performance and its operation. To solve the above problems, this article proposes a circuit defect detection method based on improved patch‐based support vector data description algorithm (Patch SVDD), which uses contrastive learning to enhance the feature extraction ability of neural network. An image calibration algorithm is used for calibration preprocessing to enhance the robustness of the model. The Euclidean distance between a query image patch and its nearest normal patch is defined to be an anomaly score. For verification, three defects in the PA circuit, including components missing, solder contamination and component orientation dislocation, were detected. The experimental results show that, compared with conventional method, the area under receiver operating characteristic (AUROC) of the improved anomaly detection model increased from 90.1% to 95.1%, which improves the detection accuracy effectively. [ABSTRACT FROM AUTHOR]

In this article, a compact dual‐band resonator is proposed for designing dual‐band power amplifiers (DBPAs). The proposed resonator has the characteristics of the band‐pass filters, suppressing the out‐of band signals. It is illustrated the proposed resonator has a simple circuit topology without sacrificing the performances of the DBPA. To verify the methodology, a high efficiency DBPA prototype operating at 1.72 and 3.48 GHz is fabricated and measured. The DBPA obtains a bandwidth of 100 and 50 MHz at the low and high frequency bands, respectively. The measurement results show that the DBPA delivers a saturation power of 43.1 and 40.8 dBm at 1.72 and 3.48 GHz, respectively. The measured drain efficiencies of the DBPA are 75.4% and 68.6% at 1.72 and 3.48 GHz, respectively. Meanwhile, when the DBPA is stimulated by a 20 MHz LTE signal with a peak to average power ratio (PAPR) of 7 dB, the measured adjacent channel leakage ratios are lower than −50 dBc at both 1.72 and 3.48 GHz after digital predistortion. [ABSTRACT FROM AUTHOR]

The Control of spatial electromagnetic (EM) waves has always been an attractive prospect, especially with the emergence of metasurfaces, which introduce additional manipulating methods and degrees of freedom. In this paper, a design is proposed to realize reconfigurable and programmable space channels for non‐reciprocal transmissions of EM waves through the use of active metasurface. The layout of the chessboard pattern is preferred for constructing the metasurface, which is composed of two kinds of meta‐atoms. One type of meta‐atom is independently controlled for the transmission gain, attenuation, and phase shift, while the other type is independently controlled for the transmission attenuation and phase shift only. The use of power amplifiers (PAs) to achieve transmission gain in the meta‐atoms can actualize the performance of non‐reciprocal transmissions. The programmable operations of phase shift and attenuation in meta‐atoms can dynamically establish varied spatial channels. A prototype of the active metasurface is fabricated and measured. In the measurements, multiple types of reconfigurable and programmable non‐reciprocal transmission channels are observed clearly, verifying the validity of the proposed method. [ABSTRACT FROM AUTHOR]

Aim. Development of method for design a two-level active shielding system for an industrial frequency magnetic field based on a quasi)static model of a magnetic field generated by power line wires and compensating windings of an active shielding system, including coarse open and precise closed control. Methodology. At the first level rough control of the magnetic field in open-loop form is carried out based on a quasi-static model of a magnetic field generated by power line wires and compensating windings of an active shielding system. This design calculated based on the finite element calculations system COMSOL Multiphysics. At the second level, a stabilizing accurate control of the magnetic field is implemented in the form of a dynamic closed system containing, in addition plant, also power amplifiers and measuring devices of the system. This design calculated based on the calculations system MATLAB. Results. The results of theoretical and experimental studies of optimal two-level active shielding system of magnetic field in residential building from power transmission line with a «Barrel» type arrangement of wires by means of active canceling with single compensating winding are presented. Originality. For the first time, the method for design a two-level active shielding system for an power frequency magnetic field based on a quasi-static model of a magnetic field generated by power line wires and compensating windings of an active shielding system, including coarse open and precise closed control is developed. Practical value. It is shown the possibility to reduce the level of magnetic field induction in residential building from power transmission line with a «Barrel» type arrangement of wires by means of active canceling with single compensating winding with initial induction of 3.5 µT to a safe level for the population adopted in Europe with an induction of 0.5 µT. References 53, figures 9. [ABSTRACT FROM AUTHOR]

The simulation of the steady state and the non-linear stability of a load modulated power amplifier (LMPA) driven by a random modulated generator, fully performed in the frequency domain by harmonic balance (HB) techniques, is presented. The non-linear microwave circuit and the driving pseudo-random modulated (PRM) generator are integrally defined in the frequency domain. The simulation is implemented and performed using commercially available circuit simulation software. The demodulation of the output signal of the LMPA is implemented with optimally matched filters as software-defined demodulation. The simulated dynamic results of a Quasi-MMIC GaN Doherty power amplifier (DPA) are shown and compared to the measured results with a 16-QAM driving signal at 10 MS/s. The time-domain measurement allows the validation of the new simulation technique through the comparison of both the measured and the simulated error vector magnitude (EVM), the left and right adjacent channel power ratios (ACPRs) versus the average output power. This new simulation is then called pseudo-random modulated harmonic balance (PRM-HB) simulation. The full PRM-HB simulation of an LMPA driven by a random modulated signal, performed in the frequency domain at the design circuit level, results in an advanced simulation tool in the frame of the design of RF circuits and subsystems for telecommunication applications. [ABSTRACT FROM AUTHOR]

This paper presents a highly efficient 5G New-Radio (NR) RF power amplifier module (PAM). The n77 PAM consists of a high-voltage differential-topology 2 μm GaAs HBT power amplifier, a CMOS controller, a silicon-on-insulator (SOI) switch, an integrated passive device (IPD) bandpass filter, a low-noise amplifier (LNA), and a bi-directional coupler. This PAM generates a saturation output power of 32.7 dBm including the loss of the SOI switch and output filter. The designed n77 PAM is tested with a commercial envelope tracker IC (ET-IC). The designed PAM with an ET-IC achieves an ACLR of −37 dBc at a 27 dBm output power with a DFT-s-OFDM QPSK 100 MHz NR signal and saves a dc power consumption of 950 mW compared to the APT mode. For the CP-OFDM 256QAM with the most stringent EVM requirements, it achieves an EVM of 1.22% at 23 dBm and saves 640 mW compared to the APT mode. [ABSTRACT FROM AUTHOR]

This paper introduces the structure and characteristics of an internal-matching high-power Doherty power amplifier based on GaN HEMT devices with 0.25 μm process platforms from the Nanjing Electronic Devices Institute. Through parameter extraction and load-pull testing of the model transistor, an EE_HEMT model for the 1.2 mm gate-width GaN HEMT device was established. This model serves as the foundation for designing a high-power three-stage Doherty power amplifier. The amplifier achieved a saturated power gain exceeding 9 dB in continuous wave mode, with a saturated power output of 49.7 dBm. The drain efficiency was greater than 65% at 2.6 GHz. At 9 dB power back-off point, corresponding to an output power of 40.5 dBm, the drain efficiency remained above 55%. The performance of the amplifier remains consistent within the 2.55–2.62 GHz frequency range. The measured power, efficiency, and gain of the designed Doherty power amplifier align closely with the simulation results based on the EE_HEMT model, validating the accuracy of the established model. Furthermore, the in-band matching design reduces the size and weight of the amplifier. The amplifier maintains normal operation even after high and low-temperature testing, demonstrating its reliability. In conjunction with DPD (digital pre-distortion) for the modulated signal test, the amplifier exhibits extremely high linearity (ACLR < −50.93 dBc). This Doherty power amplifier holds potential applications in modern wireless communication scenarios. [ABSTRACT FROM AUTHOR]

Dual-frequency ultrasounds have demonstrated significant potential in augmenting thermal ablation efficiency for tumor treatment. Ensuring proper impedance matching between the dual-frequency transducer and the power amplifier system is imperative for equipment safety. This paper introduces a novel dual-frequency impedance matching network utilizing L-shaped topology and employing a genetic algorithm to compute component values. Implementation involved an adjustable capacitor and inductor network to achieve dual-frequency matching. Subsequently, the acoustic parameters of the dual-frequency HIFU transducer were evaluated before and after matching, and the effects of ultrasound thermal ablation with and without matching were compared. The proposed dual-frequency impedance matching system effectively reduced the standing wave ratio at the two resonance points while enhancing transmission efficiency. Thermal ablation experiments with matching circuits showed improved temperature rise efficiencies at both frequencies, resulting in an expanded ablation zone. The dual-frequency impedance matching method significantly enhances the transmission efficiency of the dual-frequency ultrasound system at two operational frequencies, thereby ensuring equipment safety. It holds promising prospects for application in dual-frequency ultrasound treatment. [ABSTRACT FROM AUTHOR]