Maximum Frequency Research Articles

Design and Simulation of Butterworth Low-pass Filter

Filters are required to filter the signal to improve the signal-to-noise ratio. It is known that the maximum frequency of the human ear is about 20 kHz, and filtering out the signal components above 20 kHz can greatly improve the audio signal quality. Therefore, the design requires the cut-off frequency of 20 kHz. In this design, the normalized transfer function of the fourth-order Butterworth filter is obtained by using the normalization process, and the denormalization process is carried out according to the cutoff frequency of 20kHz, the transfer function of the fourth-order Butterworth filter is obtained.The idea of circuit cascade is applied to derive the parameters of the components, so that a filter that meets the design requirements is obtained, and the filter is used in the Multisim and Matlab simulation software to verify the filtering effect.

Integration of liquid crystal optical delay and mechanical stage optical delay for measurement of ultrafast autocorrelations and terahertz pulses

To improve the temporal resolution in an optical delay system that uses a conventional mechanical delay stage, we integrate an in-line liquid crystal (LC) wave retarder. Previous implementations of LC optical delay methods are limited due to the small temporal window provided. Using a conventional mechanical delay stage system in series with the LC wave retarder, the temporal window is lengthened. Additionally, the limitation on temporal resolution resulting from the minimum optical path alteration (resolution of 400 nm) of the conventionally used mechanical delay stage is reduced via the in-line wave retarder (resolution of 50 nm). Interferometric autocorrelation measurements are conducted at multiple laser emission frequencies (349, 357, 375, 394, and 405 THz) using the in-line LC and conventional mechanical delay stage systems. The in-line LC system is compared to the conventional mechanical delay stage system to determine the improvements in temporal resolution relating to maximum resolvable frequency. This work demonstrates that the integration of the in-line LC system can extend the maximum resolvable frequency from 375 to 3000 THz. The in-line LC system is also applied for measurement of terahertz pulses.

Designing process and analysis of a new SOI-MESFET structure with enhanced DC and RF characteristics for high-frequency and high-power applications.

This research introduces a new designing process and analysis of an innovative Silicon-on-Insulator Metal-Semiconductor Field-Effect (SOI MESFET) structure that demonstrates improved DC and RF characteristics. The design incorporates several modifications to control and reduce the electric field concentration within the channel. These modifications include relocating the transistor channel to sub-regions near the source and drain, adjusting the position of the gate electrode closer to the source, introducing an aluminum layer beneath the channel, and integrating an oxide layer adjacent to the gate. The results show that the AlOx-MESFET configuration exhibits a remarkable increase of 128% in breakdown voltage and 156% in peak power. Furthermore, due to enhanced conductivity and a significant reduction in gate-drain capacitance, there is a notable improvement of 53% in the cut-off frequency and a 28% increase in the maximum oscillation frequency. Additionally, the current gain experiences a boost of 15%. The improved breakdown voltage and peak power make it suitable for applications requiring robust performance under high voltage and power conditions. The increased maximum oscillation frequency and cut-off frequency make it ideal for high-frequency applications where fast signal processing is crucial. Moreover, the enhanced current gain ensures efficient amplification of signals. The introduced SOI MESFET structure with its modifications offers significant improvements in various performance metrics. It provides high oscillation frequency, better breakdown voltage and good cut-off frequency, and current gain compared to the traditional designs. These enhancements make it a highly desirable choice for applications that demand high-frequency and high-power capabilities.

Load frequency stabilization of distinct hybrid conventional and renewable power systems incorporated with electrical vehicles and capacitive energy storage

Maintaining a power balance between generation and demand is generally acknowledged as being essential to maintaining a system frequency within reasonable bounds. This is especially important for linked renewable-based hybrid power systems (HPS), where disruptions are more likely to occur. This paper suggests a prominent modified “Fractional order-proportional-integral with double derivative (FOPIDD2) controller” as an innovative HPS controller in order to navigate these obstacles. The recommended control approach has been validated in power systems including wind, reheat thermal, solar, and hydro generating, as well as capacitive energy storage and electric vehicle. The improved controller’s performance is evaluated by comparing it to regular FOPID, PID, and PIDD2 controllers. Furthermore, the gains of the newly structured FOPIDD2 controller are optimized using a newly intended algorithm terms as squid game optimizer (SGO). The controller’s performance is compared to benchmarks such as the grey wolf optimizer (GWO) and jellyfish search optimization. By comparing performance characteristics such as maximum frequency undershoot/overshoot, and steadying time, the SGO-FOPIDD2 controller outperforms the other techniques. The suggested SGO optimized FOPIDD2 controller was analyzed and validated for its ability to withstand the influence of power system parameter uncertainties under various loading scenarios and situations. Without any complicated design, the results show that the new controller can work steadily and regulate frequency with an appropriate controller coefficient.

Impact of molybdenum disulfide diffused coir fiber on the physical, mechanical, thermal, and vibrational characteristics of polyester composites

AbstractThis research focuses on comparing the properties of molybdenum disulfide (MoS2) diffused coir fiber polyester composites (MCF‐PCs) with neat coir fiber polyester composites (NCF‐PCs) and exploring its applications in various industrial sectors such as automotive, construction and manufacturing, where mechanical strength and fire resistance are critical factors. The study aims to investigate the physical, mechanical, thermal degradation, fire performance, and vibration properties of these composites. Compression molding was used to develop composites with different coir fiber loadings (10%, 20%, and 30% by weight). MoS2 nanoparticles diffused on the fiber surface significantly improved mechanical characteristics, thermal stability, and fiber‐matrix compatibility. The findings indicate better crystallinity and physical properties in MCF‐PCs compared to NCF‐PCs. Morphological observations confirmed improved fiber‐matrix compatibility in MoS2‐diffused fiber composites with polyester. The MCF‐PC with 20% loading exhibited the highest tensile (28 ± 1.24 MPa), flexural (50 ± 0.50 MPa), and impact (15 ± 1.01 kJ/m2) strength. The flame retardancy of the composites was evaluated using a horizontal combustion test apparatus. In addition, MCF‐PCs exhibited better flame retardancy as evidenced by lower flame propagation velocity (9 ± 0.20 mm/min) and increased ignition time (13 ± 0.29 Sec). The MCF‐PC with 20% loading shows maximum natural frequencies of 77 ± 4.1 Hz.Highlights This study investigated MoS2‐diffused coir fiber‐reinforced polyester composites. Fiber‐matrix adhesion can be improved with modified fiber‐reinforced composites. The MoS2 diffusion on fibers improved the physical and mechanical properties of polyester composites. The MoS2 diffusion on fibers enhanced the thermal and vibrational characteristics of polyester composites. MoS2‐diffused natural fiber composites offer considerable research potential.

Influence of Prestress on Vibration Frequency of Beam String Structures Based on Exact Matrix Stiffness Method

Beam string structures (BSS) are frequently employed in large-span spatial structures due to their high load-carrying efficiency and elegant appearance. Owing to the neglect of the influence of prestress, the natural frequency of the BSS is often overestimated which could be crucial to the dynamic behavior of BSS. This paper presents an exact matrix stiffness analysis method (MSM) for investigating the relationship between prestress and the natural frequency of the planar BSS. A novel dynamic stiffness matrix of beam–columns considering the natural frequency and axial force is used to develop the MSM. The dynamic analysis of the structural vibration stability of BSS is performed by using the global structural stiffness matrix which is assembled from the element stiffness matrices in the global coordinate system. The proposed MSM with the exact dynamic element stiffness matrix for the dynamic analysis of the BSS is verified by comparing with previous results based on the finite element method. The illustrative examples demonstrate that the prestress in the cable has a negative effect on the natural frequency of the BSS and should be considered in the dynamic analysis. As the axial force increases from zero to the buckling load [Formula: see text], the natural frequency of the BSS decreases from the maximum vibration frequency to zero. The influence of prestress on the vibration frequencies of BSS is particularly significant when the prestress to balance the loads is large, especially in the case of large dead and live loads (e.g. floor slabs).

A Comparative Study of the Antiemetic Effects of α2-Adrenergic Receptor Agonists Clonidine and Dexmedetomidine against Diverse Emetogens in the Least Shrew (Cryptotis parva) Model of Emesis.

In contrast to cats and dogs, here we report that the α2-adrenergic receptor antagonist yohimbine is emetic and corresponding agonists clonidine and dexmedetomidine behave as antiemetics in the least shrew model of vomiting. Yohimbine (0, 0.5, 0.75, 1, 1.5, 2, and 3 mg/kg, i.p.) caused vomiting in shrews in a bell-shaped and dose-dependent manner, with a maximum frequency (0.85 ± 0.22) at 1 mg/kg, which was accompanied by a key central contribution as indicated by increased expression of c-fos, serotonin and substance P release in the shrew brainstem emetic nuclei. Our comparative study in shrews demonstrates that clonidine (0, 0.1, 1, 5, and 10 mg/kg, i.p.) and dexmedetomidine (0, 0.01, 0.05, and 0.1 mg/kg, i.p.) not only suppress yohimbine (1 mg/kg, i.p.)-evoked vomiting in a dose-dependent manner, but also display broad-spectrum antiemetic effects against diverse well-known emetogens, including 2-Methyl-5-HT, GR73632, McN-A-343, quinpirole, FPL64176, SR141716A, thapsigargin, rolipram, and ZD7288. The antiemetic inhibitory ID50 values of dexmedetomidine against the evoked emetogens are much lower than those of clonidine. At its antiemetic doses, clonidine decreased shrews' locomotor activity parameters (distance moved and rearing), whereas dexmedetomidine did not do so. The results suggest that dexmedetomidine represents a better candidate for antiemetic potential with advantages over clonidine.

A Cross-Process Signal Integrity Analysis (CPSIA) Method and Design Optimization for Wafer-on-Wafer Stacked DRAM.

A multi-layer stacked Dynamic Random Access Memory (DRAM) platform is introduced to address the memory wall issue. This platform features high-density vertical interconnects established between DRAM units for high-capacity memory and logic units for computation, utilizing Wafer-on-Wafer (WoW) hybrid bonding and mini Through-Silicon Via (TSV) technologies. This 3DIC architecture includes commercial DRAM, logic, and 3DIC manufacturing processes. Their design documents typically come from different foundries, presenting challenges for signal integrity design and analysis. This paper establishes a lumped circuit based on 3DIC physical structure and calculates all values of the lumped elements in the circuit model with the transmission line model. A Cross-Process Signal Integrity Analysis (CPSIA) method is introduced, which integrates three different manufacturing processes by modeling vertical stacking cells and connecting DRAM and logic netlists in one simulation environment. In combination with the dedicated buffer driving method, the CPSIA method is used to analyze 3DIC impacts. Simulation results show that the timing uncertainty introduced by 3DIC crosstalk ranges from 31 ps to 62 ps. This analysis result explains the stable slight variation in the maximum frequency observed in vertically stacked memory arrays from different DRAM layers in the physical testing results, demonstrating the effectiveness of this CPSIA method.

Optimizing ultrasound Doppler measurement precision: a comprehensive experimental approach

Experimental studies were conducted utilizing advanced equipment comprising a generator, tubing system, pump module, sonographer, and PC. The generator serves as the central component connected by tubes to the pump, forming a closed circuit. A tee in the tubing set prevents Doppler fluid leakage, with the fluid poured through a special funnel into the circuit post-connection. The Doppler fluid is evenly mixed by shaking its bottle to enhance signal strength. The entire system is sealed. The centrifugal pump generates continuous flows; different power modes were tested for 30 minutes each, with frequency shifts measured at angles α=15°, 30°, and 60°. Pump disconnection from the power supply prevents liquid entry during tubing connection. The pump module housing includes ventilation holes. A 3 by 8 cm Doppler prism, treated with ultrasonic gel, was connected to the tubing to capture data. A sonographer emitting signals at 2 MHz, with a gain range of 10 to 40 dB, was utilized for sound spectra analysis. High-mode operation, 4 microseconds pulse duration, and a 32 microseconds receiver gate were set. The ultrasound apparatus dimensions were 230 x 236 x 168 mm, with a power consumption of 27 VA. Data visualization was facilitated by an LED panel, with adjustable acoustic signal volume. A USB interface enabled connection to a PC for ease of use and data analysis. Special software facilitated graph generation depicting frequency vs. time dependence measurements. Frequency analysis yielded average (f-mean) and maximum (f-max) frequency values, with f-mean utilized to measure Doppler effect frequency shift. The presented data showcases various pump speeds and incidence angles, each yielding distinctive frequency characteristics.

GaN-HEMT Performance Enhancement

In this work, a simulation analysis and calibration are carried out to improve the performance of AlGaN/GaN- MOSHEMTs (Metal-Oxide Semiconductor High Electron Mobility Transistors). The effect of the AlGaN layer thickness, gate length, Al mole fraction, and the interface traps on the electrical performance of the device has been presented. Device simulations have been done using Sentaurus technology computer-aided design (TCAD). The simulations and analysis show better drain current, transconductance, and cut-off frequency performance. The maximum cut-off frequency shown by the proposed HEMT device is 45.7 GHz at 100-nm gate length. Good transcoductance has been obtained by scaling down the gate length of the device, which is ascribed to the present two-dimensional electron gas (2DEG) density that supports upgrading the output current. Higher drain current is achieved without using acceptor-like traps in the Al2O3/AlGaN interface. Results show that the Al2O3/AlGaN/GaN-based MOSHEMT is a promising device for high-frequency and power electronic applications.

The Possible Synergistic Pharmacological Effect of an Oral Berberine (BBR) and Curcumin (CUR) Complementary Therapy Alleviates Symptoms of Irritable Bowel Syndrome (IBS): Results from a Real-Life, Routine Clinical Practice Settings-Based Study.

Irritable bowel syndrome (IBS) is a prevalent chronic functional gastrointestinal disorder, characterised by recurrent abdominal discomfort and altered bowel movements. IBS cause a significantly negative impact on quality of life (QoL). Growing pharmacological evidence suggests that berberine (BBR) and curcumin (CUR) may mitigate IBS symptoms through multiple complementary synergistic mechanisms, resulting in the attenuation of intestinal inflammation and regulation of bowel motility and gut functions. In the present observational study conducted under real-life routine clinical practice settings, 146 patients diagnosed with IBS were enrolled by general practitioner clinics and pharmacies in Belgium. For the first time, this study assessed the potential synergistic pharmacological effect of a combined oral BBR/CUR supplement (Enterofytol® PLUS, containing 200 mg BBR and 49 mg CUR) (two tablets daily for 2 months), serving as complementary therapy in the management of IBS. Following the 2-month supplementation, significant improvements were observed in the patients' IBS severity index (IBSSI) (47.5%) and all the primary IBS symptoms, such as abdominal discomfort (47.2%), distension (48.0%), intestinal transit (46.8%), and QoL (48.1%) (all p < 0.0001). The improvement in the patients' IBSSI was independent of age, sex, and IBS sub-types. The patients' weekly maximum stool passage frequency decreased significantly (p < 0.0001), and the stool status normalized (p < 0.0001). The patients' need for concomitant conventional IBS treatment decreased notably: antispasmodics by 64.0% and antidiarrhoeals by 64.6%. Minor adverse effects were reported by a small proportion (7.1%) of patients, mostly gastrointestinal. The majority (93.1%) experienced symptom improvement or resolution, with a high satisfaction rate (82.6%) and willingness to continue the supplementation (79.0%). These findings support the potential synergistic pharmacological role of BBR and CUR in IBS, and their co-supplementation may alleviate IBS symptoms and improve QoL.

Effect of Menstrual Cycle on Neuromuscular Efficiency and Muscular Strength in Runners

PURPOSE: The aim of this study was to examine the influence of the menstrual cycle (MC) stages on neuromuscular efficiency and muscular strength in female runners. METHODS: Three runners (females) underwent testing using a BIODEX isokinetic dynamometer concurrently with a BioPac EMG, during which peak torque, peak torque/body weight, time to peak torque, mean amplitude, median amplitude, minimum amplitude, maximum amplitude, frequency, and the p-p value were collected throughout the test. During the test, the performance variables were assessed on the quadriceps (rectus femoris) muscle and collected at speeds of 60 degrees/second and 180 degrees/second. STATISTICAL ANALYSIS: A paired-sample t-test was used to determine the correlation between neuromuscular efficiency and peak torque of the quadriceps during extension in the two MC phases. A paired-sample t-test was also used to determine the difference in neuromuscular efficiency between the MC phases, as well as peak torque between the MC phases. RESULTS: Muscular strength testing did not reveal statistical significance between neuromuscular efficiency and peak torque of the quadriceps during MC phases. Furthermore, there was no statistical significance between the differences in peak torque of the MC phases. Maximum amplitude at 60 degrees/second on the left leg between the MC phases revealed statistical significance (p = 0.026). EMG wave frequency at 60 degrees/second on the right leg between the MC phases revealed statistical significance (p = 0.007). CONCLUSION: Results show a significant difference in maximum amplitude and wave frequency at 60 degrees/second during knee extension between the MC phases.

Instantaneous frequency measurement system based on quantum dash mode-locked laser

We present the theory and experimental results of a microwave photonic (MWP) filter based instantaneous frequency measurement system. A quantum dash mode-locked laser is used as an optical frequency comb source. With up to 41 flat comb lines and a real-time feedback loop for comb shaping, a set of MWP filters with linear frequency responses for either linear unit or dB unit are experimentally demonstrated. The maximum measurement frequency can be up to 20 GHz limited by the available test-and-measurement instruments. By using one MWP filter, the root-mean-square error is 51∼66 MHz, which can be improved to 42.2 MHz for linear unit, and 30.7 MHz for dB unit by using two MWP filters together.

A Flexible Hardware Accelerator for Booth Polynomial Multiplier

This article presents a parameterized/flexible hardware accelerator design tailored for the Booth polynomial multiplication method. The flexibility is achieved by allowing users to compute multiplication operations across various operand lengths, reaching up to 212 or 4096 bits. Our optimization strategy involves resource reuse, effectively minimizing the overall area cost of the Booth accelerator design. A comprehensive evaluation compares the proposed multiplier design with several non-digitized bit-serial polynomial multiplication accelerators. Implementation is realized in Verilog HDL using the Vivado IDE tool, featuring diverse operand sizes, and post-place and route assessments are performed on the Xilinx Virtex-7 field-programmable gate array device. For the largest considered operand size of 1024 × 1024, our Booth accelerator utilizes 1434 slices and can operate on a maximum frequency of 523.56 MHz. A single polynomial multiplication operation requires 0.977 μs and the total power consumption is 927 mW. Moreover, a comparison to state-of-the-art accelerators reveals that the proposed flexible accelerator is 1.34× faster in computation time and 1.05× more area-efficient than the recent dedicated polynomial multiplication design. Therefore, the implementation results and comparison to the state of the art show that the proposed accelerator is suitable for a wide range of cryptographic applications.

FPGA-Based High-Speed Energy-Efficient 32-Bit Fixed-Point MAC Architecture for DSP Application in IoT Edge Computing

Designing high-speed and energy-efficient blocks for image and digital signal processing (DSP) architecture is an evolving research field. This work designs a high-speed and energy-efficient multiply-accumulate (MAC) unit to augment the performance of field-programmable gate array (FPGA)-based accelerators and softcore processors. In this work, three discrete 32-bit fixed-point signed MAC architectures were designed in Verilog and synthesized for the Zynq 7000 ZedBoard to obtain efficient MAC architecture. The ultimate goal of this work is to design a fast and energy-efficient MAC unit that can achieve speed up to the DSP48 block to reduce the latency of IoT edge computing. Energy efficiency was achieved in PPG and partial product addition (PPA) for the proposed Booth radix-4 Dadda (BR4D)-based MAC. At PPG, the width of the partial product (PP) terms was optimized with Bewick’s signed extension to reduce the power consumption. At PPA, the number of PP rows reduces the critical path delay (CPD) with Dadda-based PPA. The proposed BR4D MAC unit offers a reduction in dynamic power, CPD, power-delay product (PDP) and energy-delay product (EDP) by 22%, 9%, 29% and 36%, respectively, compared to standard Booth radix-4 Wallace tree (BR4WT) based MAC. Furthermore, hybrid MACs (BR4WT and BR4D) were compared with the current state-of-the-art (SoA) designs, and it was found that the proposed BR4D MAC is 47% faster compared to the same design in SoA. The proposed BR4D was tested for frequency scaling technique by reducing the frequency in steps of 10 MHz from a maximum usable frequency (MUF) of 64 MHz to 10 MHz to evaluate the performance for low-power applications. Reducing clock frequency by 84% will reduce the power consumption at the same proportion and speed by 38%. Additionally, the proposed design helps to improve the battery life of IoT end nodes with a reduction in energy consumption and EDP by 76% and 61%, respectively.

Electrochemical oscillation behaviors of gold during its recovery from waste printed circuit boards through slurry electrolysis

Slurry electrolysis is an effective technology for recovering gold from waste printed circuit boards (WPCBs). However, electrochemical oscillation during the gold recovery process is a potential factor affecting power consumption. As a result, the potential oscillation behaviors of gold dissolution at a constant current were studied. These results showed that the periodic formation and dissolution of the Au-OH passive film on the anode induced electrochemical oscillation. The amplitude and frequency of electrochemical oscillation were affected by hydrochloric acid concentration, current intensity, electrode spacing, and sodium chloride concentration, among which the concentration of sodium chloride had a significant inhibitory effect. Under the following conditions: hydrochloric acid concentration of 8 mol/L, current of 0.03 A, and electrode spacing of 1.5 cm, the obtained maximum amplitude potential and frequency were 1.17 V and 0.56 Hz, respectively. The phase space reconstruction results showed that the systems evolved between the near-linear equilibrium region and the periodic oscillation region. Different factors induced two oscillation modes: top-down and bottom-up. The top-down and bottom-up oscillations induced by current intensity, hydrochloric acid concentration, and electrode spacing reduced the relative power consumption by 11.8, 17.2, and 11.8 %, respectively, and increased the relative power consumption by 14.3, 21.2, and 30.1 %, respectively. A critical value was obtained, which varied oscillation patterns and gained a region of lower power consumption. The addition of trisodium citrate and PVP can improve gold recovery rate and current efficiency by regulating process of electrochemical oscillation. This work will provide theoretical support for recovering valuable metals from WPCBs with reduced energy consumption by controlling the external conditions to switch the oscillation mode.

Dental Service Cost Analysis Using Time-Driven Activity-Based Costing

This research has the objective to analyze dental service costs of the case study dental clinic using Time-Driven Activity-Based Costing (TDABC). The study was conducted in teaching clinic where dental services were provided by undergraduate-level dentistry students under the supervision of the teachers of Dentistry Faculty, and where there were also dental assistants on hand to provide service support. The research studied only five treatment procedures with a maximum frequency of service use, cumulatively totaling 80%, according to the Pareto principle. The research started from studying various activities in the processes of providing each category of dentistry service. Then, the dental service costs using TDABC were analyzed by estimating from two key parameters: the capacity cost rate and the time taken for each activity of the treatment procedure. The study found that Sealant Compounds, Tooth Extraction, Preventive Resin Restoration, Composite Fillings and Stainless Steel Crown had treatment costs of 623, 594, 669, 642 and 761 Thai Baht/treatment respectively. This research enabled the case study dental clinic to identify its costs for each treatment procedure, and also calculate profit and loss by comparison with income from service users. These data could also be used to determine more appropriate service charges for each category of treatment.

VLSI design for adjustable compression rate in lossless/lossy compression of EEG signal

In the realm of remote health monitoring, the compression of electroencephalography (EEG) signals at the edge holds significant importance. This paper presents a VLSI structure capable of adjustable compression rates to achieve both lossless and lossy compression of EEG data, catering to environments requiring flexible adjustment of compression types and rates. The architecture integrates two-dimensional discrete wavelet transform (2D-DWT) and the Set Partitioning in Hierarchical Trees (SPIHT). Notably, the Haar wavelet lifting structure is employed in 2D-DWT, and the SPIHT scanning sequence is optimized for enhanced resource efficiency. The proposed algorithm is validated using the CHB-MIT Scalp EEG Database, demonstrating compression ratios of ≥1.95 for normal EEG and ≥1.69 for epileptic EEG. Through synthesis and layout design in the 130 nm CMOS technology, the resulting circuit achieves a maximum clock frequency of 57 MHz and occupies an area of 81 kμm2, with an average power consumption of less than 0.71nj per data for 16-bit data. These findings affirm the efficacy of the proposed VLSI structure for achieving efficient lossless/lossy compression of edge EEG data.

Effects of parasitic gate capacitance and gate resistance on radiofrequency performance in LG = 0.15 μm GaN high‐electron‐mobility transistors for X‐band applications

AbstractThe effects of the parasitic gate capacitance and gate resistance (Rg) on the radiofrequency (RF) performance are investigated in LG = 0.15 μm GaN high‐electron‐mobility transistors with T‐gate head size ranging from 0.83 to 1.08 μm. When the device characteristics are compared, the difference in DC characteristics is negligible. The RF performance in terms of the current‐gain cut‐off frequency (fT) and maximum oscillation frequency (fmax) substantially depend on the T‐gate head size. For clarifying the T‐gate head size dependence, small‐signal modeling is conducted to extract the parasitic gate capacitance and Rg. When the T‐gate head size is reduced from 1.08 to 0.83 μm, Rg increases by 82%, while fT and fmax improve by 27% and 26%, respectively, because the parasitic gate–source and gate–drain capacitances reduce by 19% and 43%, respectively. Therefore, minimizing the parasitic gate capacitance is more effective that reducing Rg in our transistor design and fabrication, leading to improved RF performance when reducing the T‐gate head size.

Precipitation Characteristics of Easterly Waves Across the Global Tropics

AbstractTropical easterly waves (TEWs) are a recurrent mode of low‐latitude weather that are often convectively coupled and impact precipitation extremes. Previous work has examined the development of TEWs and their associated precipitation for individual seasons or regional domains, but no studies exist that document the importance of TEW precipitation globally. This study quantifies the precipitation associated with TEWs across the entire tropics using satellite (Integrated Multi‐satellitE Retrievals for the Global Precipitation Measurement [IMERG]) and reanalysis (Modern‐Era Retrospective analysis for Research and Applications, Version 2 [MERRA‐2]) data. Traditional space‐time filtering of precipitation reveals a mostly similar climatological power distribution for westward traveling, synoptic period disturbances corresponding to TEWs within all data sets. Using objective tracking, we find that areas with maximum TEW frequency such as the North Atlantic, Equatorial Pacific, and Indian Ocean have the highest accumulation of TEW‐associated precipitation. TEWs account for at most 30% of total annual precipitation in regions where they commonly occur and 1%–5% over much of the tropics. Vertically collocated storms, where the 850 and 700 hPa tracks correspond with each other, have higher conditional rain rates and indicate that waves with vertical development produce stronger and more organized convection. We find similar regional patterns using MERRA‐2 precipitation and latent heating, although the importance and contribution of TEWs to the background are reduced compared to IMERG. While the broad pattern of TEW associated precipitation in MERRA‐2 is like observations, the underestimation of rainfall contributions from TEWs, coupled with occasional false alarms in reanalysis data, suggests that MERRA‐2 does not capture organized convection within TEWs correctly.