Search

Summary: This letter presents a design method for dual‐band filtering phase shifters, which is based on E‐type networks. The dual‐band filtering function and different predetermined phase shift values are realized by E‐type networks and two delay lines. The dual‐band bandwidth and frequency ratio can be adjusted. Moreover, the dual‐band phase‐shift bandwidth has been extended. Finally, a dual‐band filtering phase shifter with simple structure and good filtering characteristics is fabricated and measured, which can provide 90 ± 5° and 225 ± 5° phase shifts at 1.75–2.58 GHz and 4.38–5.78 GHz, respectively. All results exhibit a good agreement between the electromagnetic (EM) simulation and measurement results. [ABSTRACT FROM AUTHOR]

This paper studies the influence of the gate voltage of the power amplifier (PA) on the drain current and efficiency. This study proposes a theory of controlling input non‐linearity to improve the efficiency of PAs. The theoretical efficiency of the inverse Class F PA that controls the input nonlinearity is within the range of 77% to 97%. A new design method for the inverse Class F PA reconstructs the design of the load admittance space into a region instead of a point. To verify the validity of the proposed theory, an inverse Class F PA is designed and fabricated using a commercial 10 W GaN high electron mobility transistor (HEMT). Results of the measurement show a high drain efficiency (DE) of 78.5%, an output power of 41.6 dBm, and a large signal gain of 12.1 dB at 1.5 GHz. The overall PA's size is controlled at 80*50 mm2$$ \mathrm{m}{\mathrm{m}}^2 $$. [ABSTRACT FROM AUTHOR]

In this article, a systematic theory and design approach are presented to achieve bandwidth expansion of the Doherty power amplifier (DPA) by using extended continuous Class‐GF (ECCGF) power amplifiers (PAs) as carrier PAs. The results of the theoretical analysis indicate that compared to conventional DPA, introducing ECCGF PA as carrier PA into the DPA design can establish two larger target impedance spaces with overlapping regions for saturation and output back‐off (OBO) power levels, which can reduce the design complexity of impedance inverter networks (IINs) while achieving DPA bandwidth expansion. Based on this, the proposed design theory is validated in the design and fabrication of a prototype DPA employing the CGH40010F GaN HEMT provided by MACOM. The measured results show that under continuous wave excitation, the designed DPA delivers a saturated output power of 43.1–44.2 dBm in the range of 1.3–2.7 GHz with a relative bandwidth of 70%. The drain efficiencies of 61.2%–73.2% and 42.5%–52.7% are achieved over the entire band at the saturation and 6‐dB OBO power levels, respectively. The measured results also confirmed the theoretical findings. [ABSTRACT FROM AUTHOR]

Summary: The small signal modeling, design, fabrication, and measurement about monolithic millimeter‐wave integrated circuit (MMIC) using gallium nitride (GaN) power amplifier (PA) on silicon carbide (SiC) working at the E band are proposed in this paper. The two stage PA used customized 4 × 75 μm transistor with 100 nm T gate technology. The extraction and optimization of small signal model are based on single GaN high electron mobility transistor (HEMT)'s measurement. Balanced structure and new method are used by low impedance matching, which can simplify circuits prominently and benefit for die size reduction. Radial stub and LC stub are made the whole circuit in absolute stable status; the in‐series DC block metal–insulator–metal capacitor from the matching circuit ensure the process is within small tolerances. From the 61–66 GHz bandwidth, a peak 10.7 dB small signal gain is obtained from the designed MMIC GaN PA, and also, the maximum output power can reach 29.7 to 30.4 dBm from 61 to 66 GHz, with an associated the peak drain efficiency of 18.8%. The final die size without dicing slot is 3.0 × 1.74 mm2. [ABSTRACT FROM AUTHOR]

Summary: An off‐chip compensation technology for low‐loss and broadband characteristics of radio frequency (RF) switches is proposed based on mathematical analysis of series shunt single pole double throws switches in this letter. This compensation technology can absorb the parasitic parameters of the switch Field Effect Transistor, improving the insertion loss and return loss of the switch as well as supporting higher bandwidth. To verify the design principle, a RF switch, using the SANAN GaAs 0.15 um pseudomorphic High Electron Mobility Transistors (pHEMT) process, and an off‐chip compensation network were designed and implemented. Specifically, after using an off‐chip compensation network, the measured bandwidth of switch has been expanded from 1.1–8.8 to 0.8–11 GHz, while the input and output return loss have also improved significantly. [ABSTRACT FROM AUTHOR]

A versatile method is invented to self‐assemble gold nanoparticles (GNPs) into nanoclusters (NCs) of various morphologies. By storing the particles in toluene, a highly non‐polar solvent, under conditions that ensure particle stability, the success rate of subsequent assembly can be enhanced. Additionally, conducting particle self‐assembly at a stirring speed of 200 rpm allows the NCs to maintain a spherical shape. The relative standard deviation (RSD) of Raman spectral peaks of multiple NCs used as surface‐enhanced Raman spectroscopy (SERS) substrates is calculated to be less than 10%, effectively addressing the issue of low repeatability when using NCs as SERS substrates. Furthermore, even at an analyte concentration reduced to 10−9 m, a SERS characteristic peak intensity of approximately 2 × 103 is measurable, demonstrating the high sensitivity of the assembled structures. Finally, by detecting SERS signals from NCs of varying sizes, the intensities of characteristic peaks tend to converge, eliminating the influence of morphology and size on SERS detection. [ABSTRACT FROM AUTHOR]

AlGaN/GaN high-electron-mobility transistors (HEMTs) are widely used in high-frequency and high-power applications owing to the high two-dimensional electron gas (2DEG) concentration. However, the microscopic origin of the 2DEG remains unclear. This hinders the development of device fabrication technologies, such as threshold voltage modulation, current collapse suppression, and 2DEG concentration enhancement technologies, as well as AlGaN/GaN sensors with very high sensitivity to polar liquids. To clarify the 2DEG microscopic origin, we studied the effects of gas molecules on AlGaN/GaN surfaces through various experiments and first-principles calculations. The results indicated that the adsorption of gas molecules on the AlGaN/GaN surface is an important phenomenon, clarifying the microscopic origin of the 2DEG. This study elucidates the properties of AlGaN/GaN heterojunctions and promotes the development of new fabrication technologies for AlGaN/GaN devices. [ABSTRACT FROM AUTHOR]

Summary In this paper, a systematic research of the effects of second source harmonics caused by gate‐source capacitance in the design of a series of continuous mode (SCM) power amplifiers (PAs) is first presented. The research results show that, compared to the conventional SCMs that require the input second harmonic to be short circuited, SCMs under the impact of input nonlinearity have a more flexible input second harmonic manipulation space, and to further improve and maintain the performance of PAs in wideband operations, a new impedance design space is explored through analysis. For practical validation, SCMs PA considering the effects of the input nonlinearity is designed and fabricated with a 10‐W gallium nitride (GaN) device, acquiring 39.1–42 dBm output power and 60.6–71.5% drain efficiency (DE) performance at a 3 dB gain compression level operating over the 0.5–3.5 GHz frequency range with a relative bandwidth of 150%. [ABSTRACT FROM AUTHOR]

Colloidal gold nanorods (GNRs) have demonstrated their potential to absorb light within specific wavelength bands and induce photothermal effects. However, the unpredictability and lack of adjustability in the broadband spectrum formed by the self-assembly of gold nanospheres or the coupling of various sizes of GNRs have posed significant challenges. To address this, we have developed broadband GNRs (BGNRs) with a predictable and adjustable extinction band in the visible and near-infrared regions. The BGNRs were synthesized by simply mixing GNRs with different aspect ratios, allowing for control over the bandwidths and positions of the extinction bands. Subsequently, the BGNRs were coated with silica and underwent surface modification. The resulting BGNRs@SiO2 were then mixed with either polydimethylsiloxane (PDMS) or polyvinylidene fluoride (PVDF) to create BGNRs@SiO2/PDMS (or PVDF) films. The BGNRs@SiO2/PDMS and BGNRs@SiO2/PVDF films both exhibit excellent photothermal performance properties. Additionally, the light absorption intensity of the BGNRs@SiO2/PVDF film linearly increases upon folding, leading to significantly enhanced photothermal performance after folding. This work demonstrates that plasmonic colloidal GNRs, without the need for coupling, can yield predictable and adjustable extinction bands. This finding holds great promise for future development and practical applications, particularly in the transfer of these properties to films. [ABSTRACT FROM AUTHOR]

The poor ion transport kinetics and serious volumetric change of transition metal sulfides hinder their electrochemical applications. In this study, we introduced a heterostructure between CoS2 and V2O3 as an anode of sodium-ion batteries (SIBs) via a feasible hydrothermal method combining with a biomass carbon derived from coffee grounds (CG). The as-prepared CoS2/V2O3-CG composite retained a reversible capacity of 464.5 mAh g−1 after 300 cycles at 0.5 A g−1, which exhibited an excellent rate capability of up to 8 A g−1 and a remarkable long-cycling life of over 2000 cycles at 2 A g−1 with a capacity decay rate of less than 0.041% per cycle. The kinetic analysis indicated that CoS2/V2O3-CG composite exhibited a superior capacitive behavior, making it a high Na+ diffusion coefficient in SIBs. The enhanced electrochemical performances of composite can be primarily attributed to the CoS2/V2O3 heterostructure and porous biomass-derived carbon, which offers a built-in electric field and a large surface area and effectively alleviates the volumetric expansion effect. [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]

A distributed basic matching network (MN) designed method that can achieve multioctave bandwidth and highly efficient power amplifier (PA) for multiband applications is presented in this letter. The distributed network unit with a left-rotating T-type structure is employed to construct the wideband MN, whose topology and circuit parameters are acquired through optimization. Finally, the impedance realized by the designed MN falls into the target impedance region obtained by using multi-harmonic bilateral pull technique in the desired frequency band. For the proof of the method, a broadband highly efficient PA has been designed, fabricated, and measured using commercialized GaN high electron mobility transistors (HEMT). The measured results show that the implemented PA achieves a bandwidth of 137.8% from 0.7 to 3.8 GHz. The drain efficiency is between 59% and 70% with an output power of greater than 39 dBm and a gain ranging from 9 to 12.1 dB. [ABSTRACT FROM AUTHOR]