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A bunching system utilizing a heterodyne combiner is designed to generate a sawtooth waveform with three harmonics to increase the beam current intensity of medical cyclotron accelerators. The design incorporates a low-pass filter, helical bandpass filters, and a broadband matching network, producing a sawtooth waveform exceeding 1200 V, which meets the requirements for efficient bunching. This buncher substitutes the design and manufacturing requirements for high linearity broadband power amplifiers with three narrowband single-frequency power amplifiers for amplification. The digital direct synthesizer achieves coherent amplitude and phase adjustment of these three frequency signals. The broadband matching network is based on transmission line transformers to avoid the design of large-sized coaxial resonant cavities, which satisfy the spatial constraints of the cyclotron injection line. [ABSTRACT FROM AUTHOR]

In this paper, 5G communication system requires high broadband, high efficiency, low distortion, and good heat dissipation for RF power amplifier. A GaN RF power amplifier working in broadband is designed. The input and output matching is processed on the Al2O3 ceramic substrate with bond wire, and the tube shell is packaged with CuMoCu copper alloy shell. Because the power loss of the power amplifier will produce a lot of heat, the heat dissipation problem becomes a factor that cannot be ignored in the design. Using the finite element thermal simulation analysis method, the maximum temperature of the power amplifier chip under long time operation is 85◦, which meets the heat dissipation demand. Under the continuous wave test conditions, the drain voltage is 30 V; the operating frequency band is 2 ∼ 6 GHz; the saturation output power is 42 dBm; the power gain is more than 45 dB; and the power added efficiency is 40%. The test results meet the actual demand. [ABSTRACT FROM AUTHOR]

This review paper examines the advancements in solid-state power amplifiers (SSPAs) for wireless communication technology. As mobile devices rely on efficient power amplifiers to maintain battery life and ensure clear signal transmission, fabrication technologies like complementary metal–oxide–semiconductor (CMOS) and gallium nitride (GaN) are revolutionizing power amplifier (PA) design. The choice of material depends on the working frequency, with gallium arsenide (GaAs) and GaN suitable for frequencies under 100 GHz, and indium phosphide reaching up to 500 GHz. However, cost is a crucial factor in industrial manufacturing, making CMOS technology advantageous for on-chip system integration. Millimeter-wave chips have different requirements based on their application scenarios. In the Ka-band (26.5–40 GHz), high-power GaN and GaAs chips are preferred for satellite and long-distance communication. In contrast, the 60 GHz band is suited for short-distance high-speed communication and consumer electronics, making lower-cost CMOS and germanium silicon devices the preferred choice. This paper explores critical design considerations for SSPAs, focusing on common structures like envelope tracking, Doherty amplifiers, envelope elimination and restoration, and various linearization methods. We provide a clear comparison of their strengths and weaknesses to empower readers to select the optimal SSPA structure for their needs. Our review aims to facilitate informed decisions in the development of efficient and cost-effective SSPAs for advancing wireless communication technology. [ABSTRACT FROM AUTHOR]

Bismuth (Bi)‐doped glass fibers are being developed into next‐generation broadband amplifiers and tunable lasers. Yet, the well‐developed Bi‐doped fiber devices only realize silica‐based optical fibers prepared by the modified chemical vapor deposition method, which faces challenges such as low doping concentration, high cost, intricate device structure, and high preparation difficulty. Here, a novel highly Bi‐doped multicomponent phosphate glass was developed. The high ion solubility of this phosphate glass facilitates achieving a Bi doping concentration of 8 mol%. The introduction of aluminum nitride (a new reducing agent) can create a local reducing environment, further increasing the concentration of low‐valence near‐infrared (NIR) active Bi ions. Furthermore, the resulting enhanced highly Bi‐doped multicomponent phosphate glass with efficient 900–1600 nm NIR emission can be drawn into corresponding optical fibers by a rod‐in‐tube method. Broadband NIR amplified spontaneous emission with a 3 dB bandwidth of 275 nm was achieved in this new fiber. As far as we know, this is the first successful preparation of Bi‐doped multicomponent phosphate glass fiber. Our results indicate that this fiber will be a powerful alternative to Bi‐doped silica‐based fibers for the preparation of related Bi‐doped fiber devices. [ABSTRACT FROM AUTHOR]

We present a systematic and rigorous analytical approach, based on the transfer matrix methodology, to study the existence, evolution, and robustness of subwavelength topological interface states in practical multilayered vibroacoustic phononic lattices. These lattices, composed of membrane-air cavity unit cells, exhibit complex band structures with various bandgaps, including Bragg, band-splitting induced, local resonance, and plasma bandgaps. Focusing on the challenging low-frequency range and assuming axisymmetric modes, we show that topological interface states are confined to Bragg-like band-splitting induced bandgaps. Unlike the Su-Schrieffer-Heeger model, the vibroacoustic lattice exhibits diverse topological phase transitions across infinite bands, enabling broadband, multi-frequency vibroacoustics in the subwavelength regime. We establish three criteria for the existence of these states: the Zak phase, surface impedance, and a new reflection coefficient concept, all derived from transfer matrix components. Notably, we provide an explicit expression for the exact location of topological interface states within the band structure, offering insight for their predictive implementation. We confirm the robustness of these states against structural variations and identify delocalization as bandgaps narrow. Our work provides a complete and exact analytical characterization of topological interface states, demonstrating the effectiveness of the transfer matrix method. Beyond its analytical depth, our approach provides a useful framework and design tool for topological phononic lattices, advancing applications such as efficient sound filters, waveguides, noise control, and acoustic sensors in the subwavelength regime. Its versatility extends beyond the vibroacoustic systems, encompassing a broader range of phononic and photonic crystals with repetitive inversion-symmetric unit cells. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study on the design and performance of a high-power amplifier (PA) covering a broad frequency band from 0.1 to 4.8 GHz. Leveraging a 10 W GaN device, the amplifier achieves output power levels surpassing 10 W across the entire frequency band. Furthermore, the power-added efficiency (PAE) of the amplifier ranges from 47% to 59%, indicating its energy-efficient operation. With consistent gain characteristics varying between 7 and 15 dB, the design ensures reliable signal amplification for diverse applications. Notably, the approach introduces a simplified output matching network based on an LC network, prioritizing practicality without sacrificing performance. Additionally, comprehensive guidance is provided on utilizing the Smith chart for streamlined amplifier design, enabling engineers with an accessible methodology. Through a meticulous analysis, this work contributes to advancing the field of high-power amplification, offering enhanced performance and usability for next-generation wireless communication systems. [ABSTRACT FROM AUTHOR]

This paper conducts a validation of two linearization approaches that utilize baseband nonlinear linearization signals of the 2nd order, through practical experiments on an asymmetrical two-way microstrip Doherty amplifier (ADA), and simulations on a symmetrical two-way Doherty amplifier (DA) as well as the single stage power amplifier (PA) for the post-OFDM 5G modulation formats. In the first approach, linearization signals are led at the input and output of the carrier transistor in the DA, while in the second approach, they are injected at the outputs of both the carrier and peaking amplifiers. The DA was tested in simulation for the FBMC signal of 20 MHz bandwidth, while the experimental measurements were performed for the FBMC signal on the ADA for different useful signal frequency bandwidths, 5 MHz, 7.5 MHz, and 10 MHz. The maximal improvement of DA linearity obtained in simulation is 10 dB for lower power and 5 dB for maximum amplifier output power, while the second approach gives around 2 dB better results for higher power levels. The experimental test for ADA performed for considered signal bandwidths indicates 3 dB to 5 dB linearity improvement for the implemented approaches and more symmetrical results achieved by the second approach. Additionally, the simulation tests for the PA were carried out for the FBMC, UFMC, and FOFDM signals of 100 MHz bandwidth, with the application of the first linearization approach. The minimal achieved linearization improvement is 13 dB for the FOFDM signal and a maximal of 18 dB for the FBMC signal. [ABSTRACT FROM AUTHOR]

The paper explores the investigation of an inverse Class‐E amplifier featuring a series output filter across various switch‐off duty ratios D. Analysis of different duty ratios as a design parameter reveals their impact on peak switch voltage, output power capability, and maximum operating frequency. Notably, it is demonstrated that adjusting the D ratio affects these parameters, with specific emphasis on achieving a maximum normalized switch voltage lower than 2 and an output power capability exceeding 0.1 for D = 0.7. Furthermore, the paper considers both parasitic shunt capacitance and series inductor in the load network, a departure from previous works that solely focused on the series inductor. The proposed circuit is highlighted for its ease of implementation compared with conventional reactance compensation circuits employing parallel resonant circuits, which are challenging to form directly. An innovative approach is introduced to showcase the broadband performance of the inverse Class‐E amplifier. The measured drain efficiency and output power versus input power at 430 MHz are 82% and 45.3 dBm, respectively. A similar performance can be achieved within the frequency range of 380–600 MHz by proper tuning at saturated power. The measurement results demonstrate a maximum high power‐added efficiency (PAE) of 79% and drain efficiency of 82% within this frequency range, accompanied by a gain exceeding 12.0 dB and output power surpassing 44 dBm. [ABSTRACT FROM AUTHOR]

In this paper, a GaN high-electron-mobility transistor (HEMT) compact high-power wide-band power amplifier with an operation frequency from 0.8 GHz to 2 GHz is proposed. In order to realize a compact design, an internally matched method is employed. A wide-band matching strategy with an LC network and a multi-stage wide-band power combiner/divider is introduced in this design to achieve a wide bandwidth. A power combination structure is applied to have high output power. Wire-spiral inductance and film capacitors are employed to construct the compact matching network. The equivalent inductance of the bonding wire is also involved in the matching network. Experimental results show that the PAE (power-added efficiency) during the whole operation's bandwidth (0.8 GHz to 2.0 GHz) is from 40% to 57%. The output power can reach from 48.3 dBm to 49.8 dBm with a circuit size of 30.8 × 27.4 mm 2 . [ABSTRACT FROM AUTHOR]

This paper discusses the challenges faced by existing power amplifier configurations in meeting the bandwidth requirements of modern communication technology while maintaining high efficiency due to the overlap of fundamental and harmonic frequencies. To address this issue, the paper proposes a matching method based on mode combination theory that utilizes the overlap of harmonic and fundamental impedance to simplify the design of broadband amplifiers. In this paper, a Chebyshev low-pass filter is used to control the higher harmonics instead of the conventional quarter-wavelength harmonic control network with a combination of harmonic impedances. The proposed method combines three modes of Resistive-Reactive class F [-1], class J, and class F power amplifiers, which can achieve high efficiency and octave frequency at the same time. The paper verifies the proposed method by designing and fabricating a multimultiplier power amplifier with a drain efficiency of 61.8-73.9%, an operating bandwidth of 1.4-2.9 GHz, and a saturation output of 41.1-42.3 dBm. The amplifier also has a gain greater than 11.1-12.3 dBm, and at an output power of 36 dBm, the ACPR value is -32 to -33.1 dBc across the band. [ABSTRACT FROM AUTHOR]

With the emergence of GigaHertz applications in microwave systems, the design of the broadband amplifiers became a big challenge especially with the implementation in silicon CMOS process. This paper presents a new design scheme for these amplifiers using the distributed matrix amplifier concept. The new scheme reduces the total number of the amplifier's inductors by replacing the conventional T portions in the transmission lines with the π portions. The potential benefits of the new technique over the classical matrix amplifier designs are: very high and stable gain, onchip area saving, and less parasitic-aware optimization steps. Taking the advantages of the proposed methods, a four-stage amplifier has been carefully designed using 0.13μm standard CMOS technology. As a comparison with the previous matrix amplifiers, the new design achieved the best gain-bandwidth product in smallest on chip area. [ABSTRACT FROM AUTHOR]

Bismuth (Bi)‐doped glass and fiber materials exhibit excellent optical performance and have potential in fields such as fiber communication and tunable lasers. However, the preparation of Bi‐doped glass and fiber with high optical activity is still confronted with huge challenges. This study proposes a germanium oxide hybridization strategy to enhance near‐infrared emission in Bi‐doped glass. In addition, by the systematical optimization of the optical response and processability of the glass system, Bi‐doped glass fibers are successfully constructed. The constructed glass fibers have excellent optical performance, and the enhanced amplified spontaneous emission is realized. They show potentials for applications in broadband fiber amplifiers and tunable lasers. [ABSTRACT FROM AUTHOR]

Expanding gain bandwidth into the L-band for erbium-doped fiber amplifiers (EDFAs) is a crucial strategy to overcome limitations in prevalent C-band focused commercial silica-based EDFAs, significantly boosting optical network transmission capacity. Herein, we synthesized Er3+-doped broadband near-infrared emission tellurite glasses utilizing the melt quenching process, systematically exploring the impact of ZnCl 2 on the glass structure and optical properties. The 82TeO 2 –3Nb 2 O 5 –15ZnCl 2 –3Er 2 O 3 (TNZ15) glass emerged as a standout candidate for broadband amplifiers around wavelength at 1.55 μm. With escalating ZnCl 2 concentration, a discernible red shift in the emission peak wave lines was observed, accompanied by an expansion of the full width at half maximum (FWHM) from 98 nm to 106 nm. Noteworthy characteristics of all samples included exceptional thermal stability and elevated near-infrared (NIR) transmittance. Application of the Judd-Ofelt (J-O) theory facilitated the calculation of J-O parameter intensity, providing deeper insights into the optical behavior of the materials. Finally, the evaluation of TNZ15 planar optical waveguides, employing the vertical top pumping mode of two 980 nm LEDs, encompassed both the C-band (1530–1565 nm) and the L-band (1565–1625 nm). The results underscore the potential of TNZ15 glass as a promising gain material for broadband optical amplifiers and lasers, offering valuable insights into the development of next-generation optical amplification technologies. [ABSTRACT FROM AUTHOR]

Decades of measurements of the thermophysical properties of hot metals show that pulsed Joule heating is an effective method to heat solid and liquid metals that are chemically reactive or difficult to contain. To extend such measurements to hundreds of GPa pressure, pulsed heating methods have recently been integrated with diamond anvil cells. The recent design used a low-side switch and active electrical sensing equipment that was prone to damage and measurement error. Here, we report the design and characterization of new electronics that use a high-side switch and robust, passive electrical sensing equipment. The new pulse amplifier can heat ∼ 5 to 50 μm diameter metal wires to thousands of kelvin at tens to hundreds of GPa using diamond anvil cells. Pulse durations and peak currents can each be varied over three orders of magnitude, from 5 µs to 10 ms and from 0.2 to 200 A. The pulse amplifier is integrated with a current probe. Two voltage probes attached to the body of a diamond anvil cell are used to measure voltage in a four-point probe geometry. The accuracy of four-point probe resistance measurements for a dummy sample with 0.1 Ω resistance is typically better than 5% at all times from 2 µs to 10 ms after the beginning of the pulse. [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]

In this paper, a fully differential amplifier is proposed in a 1.8 V-0.18 μm CMOS (Complementary Metal-Oxide-Semiconductor) technology, which can accommodate both voltage (V-mode) and current (C-mode) inputs. Post-layout simulation results show a fixed gain amplifier exhibiting a 26 dB (V-mode)/89 dBΩ (C-mode) gain and a programmable gain amplifier featuring a 6–26 dB gain, overall yielding a 26.8–46.4 dB dB (V-mode)/89.6–109.2 dBΩ (C-mode) programmable gain range, with a 100 MHz bandwidth and a power and area consumption of 360.5 µW and 0.0177 mm2, respectively. This amplifier has been designed considering the constraints and specifications (including low voltage, low power, reduced noise and high common mode rejection ratio) for its use in an analogue Lock-in-based Frequency Response Analyser-Impedance Spectroscopy (FRA-IS) device. The proposed design introduces a novel fully differential open-loop structure based on a transconductance–transimpedance (TC-TI) topology for high performance applications with a broad programmable bandwidth. To compare this work, different figures of merit (FoMs) are introduced as well as a comparison table with other simulated and experimental results, reporting an overall better performance in terms of gain, frequency and power-area consumption. [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]

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]

This paper presents a numerical study and the optimization of very short discrete multi-pump Raman amplifiers using Tellurite-based optical fibers. While most studies about discrete Raman amplifiers usually focus on cases where hundreds of meters of fiber are used, here we consider a multi-pumped Raman amplifier setup with extremely short dimensions, in which the length of the gain media was varied from 2.5 to 30 meters. The optimization process was developed over an broad amplification band from 1520 to 1600 nm, considering a maximum acceptable ripple of 3 dB, and using 2, 3 and 4 pumps with individual powers always below 2.5 W. The results show that it is possible to achieve net gains as high as 10 dB for gain media around 20 meters, and close to 15 dB for 30 meters. These high gains highlight the fact that Tellurite-based optical fibers can be used for the construction of very short and compact broadband amplifiers using just a few pump lasers with modest optical powers. [ABSTRACT FROM AUTHOR]

This paper reports a broadband near-infrared emission ranging from 1400 to 1660 nm in Er3+-doped nanocrystal-modified PbO-PbF 2 -Bi 2 O 3 -Ga 2 O 3 glasses. After heat treatment, X-ray diffraction measurements were performed and confirmed that PbBiO 2 F nanocrystals were precipitated in the precursor glasses. As nanocrystals alter the local environment around Er3+ ions, the emission spectrum of the transition 4I 13/2 →4I 15/2 is broadened and enhanced, resulting in a broadband emission and an FWHM wavelength range of 143.4 nm from 1470.1 to 1613.5 nm, which overlaps the S+C+L optical communications windows. In addition, the emission intensity of the 4I 11/2 →4I 13/2 transition is also found to be increased after heat treatment, thus enhancing the λ∼2750 nm emission intensity. Our results indicate that an Er3+-doped nanocrystal-modified PbO-PbF 2 -Bi 2 O 3 -Ga 2 O 3 glass could be a competitive candidate material that can offer improved bandwidths for S+C+L broadband amplifiers used in very high-capacity optical communications systems. [ABSTRACT FROM AUTHOR]

This letter presents a design method of resistance reactance hybrid continuous power amplifier based on reconfigurable devices and CG2H40010F. The power amplifier combines resistive‐reactive inverse F‐class power amplifier (RRIFPA), resistive‐reactive J‐class power amplifier (RRJPA), and resistive‐reactive F class power amplifier (RRFPA). We utilize the principle of low‐pass filters to control the impedance of multi‐frequency harmonics, and use the reconfigurable device SMP1345‐079LF to expand the bandwidth of the power amplifier. This article designs and produces a 1–4 GHz broadband power amplifier. The simulation and measurement results show that within the entire frequency range of 1–4 GHz, the Drain efficiency is between 53.6 and 72.1% $ \% $, the output power is between 40.1 and 42.6 dBm, the gain is between 10.1 and 12.6 dB, and the relative bandwidth is up to 120% $ \% $. [ABSTRACT FROM AUTHOR]

A power amplifier (PA) stands as a central module within the electronic information system (EIS), and any variation in a PA's specifications has a direct impact on the EIS's performance, especially in the face of temperature fluctuations. In examining the influence of PA specification changes on the EIS, we employed support vector machine (SVM) to model the behavior of the temperature characteristics of 0.3–1.1 GHz complementary metal oxide semiconductor (CMOS) class-A broadband PAs. The results show that the parameters of S11, S12, S21, and S22 can be effectively modeled. SVM outperforms Elman and GRNN in terms of combined modeling time and modeling accuracy. This research can be extended to modeling the behavior of other types of power amplifiers or devices and circuits. [ABSTRACT FROM AUTHOR]

In this letter, a novel design method of split‐ring resonator (SRR) as the input matching network (IMN) of power amplifier (PA) is proposed. Compared with conventional microstrip lines, SRR is capable of providing necessary harmonic short‐circuit while achieving broadband impedance matching. Applying the even–odd‐mode theory, the impedance transformation characteristics of SRR are analyzed and show SRR can perform accurate impedance matching. To verify the proposed method, a PA is designed and implemented, the input impedance of 10‐W GaN transistor is well matched to the source impedance by the SRR IMN in the operation band of 1.0–3.0 GHz. The measurement results show that the maximum drain efficiency of PA can reach 79.5% with 41.8 dBm of average output power in the operation band. [ABSTRACT FROM AUTHOR]

In this paper, a compact internally matched architecture of continuous class‐B/J Doherty power amplifier is studied. The influence of symmetric generalized combiner and postmatching network with harmonic control on the bandwidth and efficiency of Doherty power amplifier (DPA) is analyzed in detail. Based on the parameters obtained from theoretical analysis, a design method of internally matched continuous mode DPA (CM‐DPA) is proposed, and a broadband DPA with a size of 22.8 mm × $\times $ 24.5 mm was developed for experimental verification. The test structure shows that the maximum output power at saturation can reach 46.2 dBm. The efficiency of 6 dB back‐off is 58%–63.4%, with good consistency. In the reliability experiment, transistor and matching circuit of the CM‐DPA have a temperature below 100°C at saturation. The output power and efficiency tested at different temperatures (25∘ $2{5}^{\circ }$C, −55∘ $-5{5}^{\circ }$C, and 85∘ $8{5}^{\circ }$C) show that the DPA has high reliability. [ABSTRACT FROM AUTHOR]

In this work, Tm3+ doped and Tm3+/Ho3+ co-doped germanate glasses with various TiO 2 concentrations have been examined using optical spectroscopy. The broad emission bands corresponding to 3F 4 →3H 6 (1.8 μm) and 5I 7 →5I 8 (2 μm) transitions of thulium and holmium ions were registered, respectively. It was observed that the intensity of near-infrared emission bands significantly changes with increasing titanium oxide content in the glass composition. Furthermore, the energy transfer process from Tm3+ to Ho3+ ions in studied glass systems was confirmed and discussed. The dependence of spectroscopic parameters like full width at half maximum (FWHM) and energy transfer efficiency (η ET) on increased TiO 2 concentration in glass host was established. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) luminescence of Pr3+ and Tm3+ ions in titanate‐germanate glasses has been studied for laser and fiber amplifier applications. The effect of the molar ratio GeO2:TiO2 (from 5:1 to 1:5) on spectroscopic properties of glass systems was studied by absorption, luminescence measurements, and theoretical calculations using the Judd–Ofelt theory. It was found that independent of the TiO2 concentration, intense NIR emissions at 1.5 and 1.8 μm were observed for glasses doped with Pr3+ and Tm3+ ions, respectively. Moreover, several spectroscopic and NIR laser parameters for Pr3+ and Tm3+ ions, such as emission bandwidth, stimulated emission cross‐section, quantum efficiency, gain bandwidth, and figure of merit, were determined. The results were discussed in detail and compared to the different laser glasses. Systematic investigations indicate that Pr3+‐doped system with GeO2:TiO2 = 2:1 and Tm3+‐doped glass with GeO2:TiO2 = 1:2 present profit laser parameters and could be successfully applied to NIR lasers and broadband optical amplifiers. [ABSTRACT FROM AUTHOR]

In this paper, a millimeter‐wave broadband high‐efficiency power amplifier (PA) for Ka‐band (26–32 GHz) using 0.15‐μm GaAs pseudomorphic high‐electron‐mobility transistor process is proposed. The PA utilizes a three‐stage cascade structure and adopts an RC series feedback network, which expands the bandwidth and ensures the circuit stability. To improve the output power and efficiency of the circuit, a tree‐like transistor structure is proposed. The power amplifier, it can provide 23.6 dBm output P1dB with 33.1% power‐added efficiency at 28 GHz with high linearity. The maximum small signal gain can reach 27 dB with 3‐dB bandwidth from 24 to 33 GHz for the measured results. [ABSTRACT FROM AUTHOR]

Purpose: Multinuclear MRI/S is of increasing interest. Currently, most multinuclear receive array coils are constructed by nesting multiple single‐tuned array coils or using switching elements to control the operating frequency, in which case more than one set of conventional isolation preamplifiers and associated decoupling circuits is required. These conventional configurations rapidly become complicated when greater numbers of channels or nuclei are needed. In this work, a novel coil decoupling mechanism is proposed to enable broadband decoupling for array coils with one set of preamplifiers. Methods: Instead of using conventional isolation preamplifiers, a high‐input impedance preamplifier is proposed to create broadband decoupling of the array elements. A matching network consisting of a single inductor‐capacitor‐capacitor multi‐tuned network and a wire‐wound transformer was used to interface the surface coil to the high‐impedance preamplifier. To validate the concept, the proposed configuration was compared to the conventional preamplifier decoupling configuration on both bench and scanner. Results: 2 The approach can provide more than 15dB decoupling over a range of 25MHz, covering the Larmor frequencies of 23Na and 2H at 4.7T. This multi–tuned prototype obtained 61% and 76% of the imaging SNR at 2H and 23Na respectively, 76 and 89% in a higher loading test phantom, when compared to the conventional single–tuned preamplifier decoupling configuration. Conclusion: With the multinuclear array operation and decoupling achieved using only one layer of array coil and preamplifiers, this work provides a simple approach of building high element‐count arrays to enable accelerated imaging or SNR improvement from multiple nuclei. [ABSTRACT FROM AUTHOR]

In this paper, the design methodology of a high-linearity wide-band transimpedance amplifier (TIA) for cable television (CATV) application is addressed. A simple four-stage topology is proposed to maintain a well-balanced linearity over a wide operating band. The regulated cascode (RGC) input stage is used to match an input impedance of 75 Ω, followed by a gain stage with enhanced bandwidth. The high-linearity output stage is able to drive the 75 Ω load directly with high output swing under a high supply voltage. The prototype is implemented with a standard 0.11μm CMOS process while occupying the silicon area of 0.034 mm2. The measurement results for the prototype show a peak gain of 76.6 dBΩ over a 3-dB bandwidth of 1.1 GHz with a considerably small gain ripple and an OIP3 of 20.4 dBm. The whole test chip consumes 447 mW DC power and the measured average input-referred noise current spectral density is 7.9 pA Hz−1/2 up to 1 GHz. [ABSTRACT FROM AUTHOR]

We report a novel PbS/Er co-doped silica fiber (PEDF) with improved spectral properties in O-band (1260–1360 nm). The results show that the gain of the PEDF exceeds 15 dB in the range of 1150–1360 nm. Compared to PbS-doped silica fiber, the PEDF has a gain improvement of 6.4–10.9 dB in O-band. In addition, the concentration of Pb and S in the PEDF core is significantly higher, and the size distribution of PbS nanoparticles is more concentrated in a narrow range. These factors may account for the enhanced gain characteristics of the PEDF. This work reveals the positive effect of co-doping Er3+ ions on the gain characteristics of the PEDF in O-band, and suggests an important research direction for the design of broadband amplifiers and light sources for optical communication with zero dispersion.

In this paper, a realization method for high-efficiency broadband power amplifier (PA) based on split-ring resonator (SRR) second harmonic output matching network (SHOMN) is presented. The SRR is composed of double rectangular rings, and it can flexibly match the second harmonic components to the high-efficiency impedance region in the Smith chart in a wide frequency band. Besides, the impedance transformation characteristic of SRR is derived, and the optimal output impedance is converted from the transistor drain to the output of SHOMN for accurate fundamental matching. For validation, a PA operating in 1.2–3.0 GHz is designed and fabricated for a 10-W GaN transistor. The measurement results show that the maximum efficiency can reach 78.3%; meanwhile, the average saturated output power is 41.0 dBm. [ABSTRACT FROM AUTHOR]

Broadband millimeter-wave power amplifiers have attracted much attention and have wide applications for 5G communication, satellite communication, radar, sensing, etc. Yet, it is challenging to design a power amplifier with broadband small-signal gain and power performance simultaneously. In this study, a transformer-based symmetrical magnetically coupled resonator (MCR) matching network for broadband output matching and stagger-tuned MCRs are used to achieve both broadband small- and large-signal performance. Also, to enhance the gain for the power amplifier, a three-stage common-source pseudo-differential structure is adopted to mitigate the low-gain issue due to stagger tuning, and the shunt resistors aimed to decrease the Q factor of the MCRs. We used the in-phase two-way current combined with microstrip transmission lines to increase the output power. Designed in 65 nm bulky CMOS technology, the power amplifier presents a 3 dB small-signal gain bandwidth from 25.8 GHz to 36.9 GHz, indicating a peak gain of 25.87 dB at 30.5 GHz. The power amplifier demonstrates a 17.84 dBm saturated output power ( P s a t ) at 31 GHz and a 24.37% peak power added efficiency ( P A E m a x ) at 28 GHz. The power amplifier achieves a flat P s a t of 17.44 ± 0.4 dBm, a P A E m a x of 22.59 ± 1.78%, and an O P 1 d B of 13.78 ± 0.31 dBm from 26 GHz to 36 GHz. [ABSTRACT FROM AUTHOR]

Summary: Wideband low‐noise amplifiers (LNAs) are widely used in 5G and 6G communication systems. This paper first analyzes two common bandwidth extension technologies: the stagger tuning technique and the magnetically coupled resonators (MCR) technique. Then, a four‐stage LNA based on double‐tuned transformer combined with stagger tuning idea and MCR idea was proposed. In order to improve the broadband characteristics of the LNA, the loose coupling double‐tuned transformer is carefully designed. Compared with the traditional stagger tuning LNA, it has better broadband characteristics, lower element error sensitivity, and lower design complexity. This designs a gain bandwidth product of 1.48 T with a −3‐dB bandwidth in 9.11 GHz and the noise factor is lower than 3 dB, which covers more than 45% −3‐dB fractional bandwidth. The LNA consumes 37‐mW power with a 1.1‐V supply and occupies 1.22 × 0.4 mm2. [ABSTRACT FROM AUTHOR]

Summary: We propose a broadband high‐efficiency power amplifier (PA) with output power between 42.6 and 44.7 dBm, drain efficiency (DE) over 62%, and power additional efficiency (PAE) over 52% in the 2.3–3.5GHz frequency band. This PA effectively combines the high‐efficiency characteristics of class‐F PAs with the advantages of controlling the second harmonic for obtaining high efficiency at large bandwidth. The Dual Band Harmonic Control and Matching Network (DBHCN) realizes the conversion from 50 Ω to high‐efficiency impedance space (HEIS) while controlling the high‐order harmonics in different frequency bands. The proposed PA can be used for the fifth‐generation mobile communication technology (5G) base stations and broadband radars. [ABSTRACT FROM AUTHOR]

Traveling salesman problem (TSP) is a decision-making problem that is essential for a number of practical applications. Today, this problem is solved on digital computers exploiting Boolean-type architecture by checking one by one a number of possible routes. In this work, we describe a special type of hardware for the TSP solution. It is a magnonic combinatorial device comprising magnetic and electric parts connected in the active ring circuit. There is a number of possible propagation routes in the magnetic mesh made of phase shifters, frequency filters, and attenuators. The phase shifters mimic cities in TSP while the distance between the cities is encoded in the signal attenuation. The set of frequency filters makes the waves on different frequencies propagate through the different routes. The principle of operation is based on the classical wave superposition. There is a number of waves coming in all possible routes in parallel accumulating different phase shifts and amplitude damping. However, only the wave(s) that accumulates the certain phase shift will be amplified by the electric part. The amplification comes first to the waves that possess the minimum propagation losses. It makes this type of device suitable for TSP solution, where waves are similar to the salesmen traveling in all possible routes at a time. We present the results of numerical modeling illustrating the TSP solutions for four and six cities. Also, we present experimental data for the TSP solution with four cities. The prototype device is built of commercially available components including magnetic phase shifters/filters, coaxial cables, splitters, attenuators, and a broadband amplifier. There are three examples of finding the shortest route between the cities for three different sets of city-to-city distances. The proposed approach is scalable to TSP with a larger number of cities. Physical limits and challenges are also discussed. [ABSTRACT FROM AUTHOR]

The design of a continuous broadband Doherty power amplifier (DPA) based on an X‐parameter model is presented in this work. The broadband load‐pull X‐parameter model is extracted at both the package plane and current generate plane of the device under test. The model cannot only predict the fundamental and harmonic nonlinear behavioral accurately, but also find the optimal output power and drain efficiency (DE) region of the Smith chart precisely, thereby assisting DPA design. A 10‐W gallium nitride packaged transistor from Wolfspeed is utilized in this design. The fabricated DPA reached a saturation output power of 44.3 dBm, with a saturation DE over 68% and a 6 dB output power back‐off efficiency over 51% in the frequency range of 1.1–1.8 GHz, verifying experimentally the effectiveness of the proposed design methodology. [ABSTRACT FROM AUTHOR]

Bismuth (Bi)‐doped glasses with broadband near‐infrared (NIR) emission have been drawing increasing interest due to their potential applications in tunable fiber lasers and broadband optical amplifiers. Yet, the implementation of highly efficient and ultra‐broadband Bi NIR emission covering the whole telecommunication window remains a daunting challenge. Here, via a metal reduction strategy to simultaneously create a chemically reductive environment during glass melting and enhance the local network rigidity, a super broadband (FWHM ≈ 600 nm) NIR emission covering the entire telecommunications window with greatly enhanced intensity was achieved in Bi‐doped germanate glasses. More importantly, due to the excellent thermal stability, the super broadband Bi NIR emission can be well retained after the glass was drawn into an optical fiber. Furthermore, the transmission loss of 0.066 dB/cm at 1310 nm and an obvious broadband amplified spontaneous emission spectrum spanning a range of 1000–1600 nm were observed in this fiber. This work can strengthen our comprehension of the complicated Bi NIR luminescence behaviors and offer a feasible and universal way to fabricate tunable fiber lasers and broadband optical amplifiers based on Bi‐doped multicomponent glasses. [ABSTRACT FROM AUTHOR]

Dense wavelength division multiplexing (DWDM) is recognized as one of the leading technologies for resolving the internet data traffic capacity issue. Although the successful development of rare-earth doped fiber amplifiers enables to achieve optical signal amplification in various telecommunication wavebands, their bandwidth is limited by the inherent sharp 4f electronic transition. Here, we propose the clustering engineering strategy in tellurium (Te)-doped glass fiber for broadband optical amplification. The correlation among the glass system, chemical state of Te and the optical response are systematically studied. The active Te-doped phosphate glass with intense and broadband luminescence is successfully achieved by control of the cluster state of the Te atoms. Subsequently, Te-activated phosphate fiber is successfully drawn and the optical response is transferred smoothly. Importantly, the amplified spontaneous emission and broadband optical amplification are achieved for the first time in Te-doped glass fiber. A small signal on-off gain covering an ultra-wide range of O + E + S + C + L bands is observed under excitation at 808 nm. Our results establish a critical step toward advancing Te-based photonic materials for novel broadband fiber amplifiers serviced in telecommunication system. [ABSTRACT FROM AUTHOR]

A compact broadband 12 W power amplifier with broadband matching networks is presented. Transistors connected in parallel are used to synthesize the high power. Input, interstage, and output matching networks are also properly designed to meet the requirement of the broadband application. The broadband high power amplifier (HPA) was fabricated using a 0.15‐μm gallium nitride (GaN) HEMT technology, with a maximum saturated measured output power of 43 dBm from 6 to 18 GHz. The measured power added efficiency exceeds 20% in the whole interested band. The proposed HPA also has a compact size of 3.1 mm × 2.96 mm. [ABSTRACT FROM AUTHOR]

To meet the application requirements of broadband radar systems for broadband power amplifiers, a Ku-band broadband power amplifier (PA) microwave monolithic integrated circuit (MMIC) based on a 0.15 µm gallium arsenide (GaAs) high-electron-mobility transistor (HEMT) technology is proposed in this paper. In this design, the advantages of the stacked FET structure in the broadband PA design are illustrated by theoretical derivation. The proposed PA uses a two-stage amplifier structure and a two-way power synthesis structure to achieve high-power gain and high-power design, respectively. The fabricated power amplifier was tested under continuous wave conditions, and the test results showed a peak power of 30.8 dBm at 16 GHz. At 15 to 17.5 GHz, the output power was above 30 dBm with a PAE of more than 32%. The fractional bandwidth of the 3 dB output power was 30%. The chip area was 3.3 × 1.2 mm2 and included input and output test pads. [ABSTRACT FROM AUTHOR]

We have developed a versatile near-field microscopy platform that can operate at high magnetic fields and below liquid-helium temperatures. We use this platform to demonstrate an extreme terahertz (THz) nanoscope operation and to obtain the first cryogenic magneto-THz time-domain nano-spectroscopy/imaging at temperatures as low as 1.8 K, magnetic fields of up to 5 T, and with operation of 0–2 THz. Our Cryogenic Magneto-Terahertz Scattering-type Scanning Near-field Optical Microscope (or cm-THz-sSNOM) instrument is comprised of three main equipment: (i) a 5 T split pair magnetic cryostat with a custom made insert, (ii) a custom sSNOM instrument capable of accepting ultrafast THz excitation, and (iii) a MHz repetition rate, femtosecond laser amplifier for broadband THz pulse generation and sensitive detection. We apply the cm-THz-sSNOM to obtain proof of principle measurements of superconductors and topological semimetals. The new capabilities demonstrated break grounds for studying quantum materials that require an extreme environment of cryogenic operation and/or applied magnetic fields in nanometer space, femtosecond time, and THz energy scales. [ABSTRACT FROM AUTHOR]

This paper presents the design procedure of an efficient compact monolithic microwave integrated circuit power amplifier (MMIC PA) in a 0.1 μm GaN-on-Si process for 5G millimeter-wave communication. Load/source-pull simulations were conducted to correctly create equivalent large-signal matching models for stabilized power cells and to determine the optimal impedance domain. The shorted stub with bypass capacitors minimizes the transistor's output reactance, simplifying the matching objective to an approximate real impedance transformation (IT). With miniaturization as the implementation guide, explicit formulas and tabulated methods based on mathematical analysis were applied to synthesize the filtering matching networks (MNs) for the input and output stages. In addition, a CAD-dependent numerical optimization approach was used for the interstage MN that needs to cope with high IT ratio and complex loads. The continuous-wave (CW) characterization for the proposed two-stage PA demonstrated 19.8 ± 0.7 dB of small-signal gain, very flat output power (Pout) and power-added efficiency (PAE) at 4 dB gain compression of 32–32.4 dBm and 34–34.6%, respectively, over 24–30 GHz, with 37.1% of peak PAE at mid-frequency. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tellurite glass with Tm3+/Ho3+/Er3+ combination was developed by melt-quenching method. • A broad luminescence from 1570 to 2200 nm with 379 nm FWHM was obtained under 808 nm pump. • Energy transfer from Er3+ to Tm3+/Ho3+ enhances broadband luminescence intensity by about 116 %. • There are potential applications in ultrashort pulse lasers and broadband amplifiers. Improving the broadband luminescent properties in ∼2 μm band has always been a serious challenge. This paper proposed a Tm3+, Ho3+ and Er3+ doped combination in tellurite glass, which was synthesized through melt-quenching and characterized by a series of physical and spectral tests. Firstly, tellurite glass of Tm3+–Ho3+ co-doping produced a ∼2 μm broadband luminescence ranging from 1570 to 2200 nm with FWHM (full width at half maximum) of 379 nm under 808 nm pumping. This broadband luminescence originated from 3F 4 to 3H 6 level transition of Tm3+ and 5I 7 to 5I 8 level transition of Ho3+. Furthermore, after adding an appropriate amount of Er3+, the luminescent intensity was improved by 116 %, mainly attributed to the direct or indirect energy transfers from Er3+ to Tm3+ and Ho3+ ions. Calculations of Judd-Ofelt spectroscopic parameters and gain cross-sections supported the results obtained from Tm3+/Ho3+/Er3+ doped tellurite glass in ∼2 μm band. In addition, DSC (differential scanning calorimetry) curves exhibited excellent thermal stability, XRD (X-ray diffraction) patterns and Raman spectra disclosed the non-crystalline and network structural units of the synthesized tellurite glasses. The findings in this work demonstrate that tellurite glass with Tm3+, Ho3+ and Er3+ combination is an efficient strategy which can be applied in ∼2 μm band ultra-short pulse lasers and broadband amplifiers. [ABSTRACT FROM AUTHOR]