Search

The influence of frequency characteristics of devices is complex. The effects of AlN barrier thickness, gate length, gate-drain spacing and work function on the frequency characteristics of AlN/ β-Ga2O3 high electron mobility transistor (HEMT) were studied by Sentaurus TCAD in this paper. The following conclusions are obtained: as the thickness of the AlN barrier layer increases from 10 nm to 25 nm, the cutoff frequency (fT) and maximum oscillation frequency (fmax ) rise by 18 and 17 GHz respectively. The decrease of gate capacitance is the main reason for the increase of fT . Furthermore, it was found that the thinner barrier layer enhanced the gate's ability to control the channel electrons. When the gate length is scaled down from 0. 9 μm to 0. 1 μm, fT and fmax increase by 84 and 98 GHz, respectively, representing a far more profound influence on frequency characteristics than the barrier layer thickness. However, when the gate length fell below 0. 1 μm, short-channel effects emerged. As the gate-drain spacing increase, fT exhibits a slight decrease. Coupled with the concurrent reduction in source resistance, this led to a synchronized trend in fmax and fT only when the gate-source voltage (VGS ) exceeds - 1. 2 V. The work function, on the other hand, has minimal impacts on fT and fmax, but an increase in the work function positively influenced the device' s pinch-off characteristics. In summary, this paper indicates that by shortening the gate length while concurrently augmenting the thickness of the AlN barrier layer, gate-drain spacing, and work function, one can enhance the frequency characteristics while also improving the pinch-off characteristics of the device, which has certain guiding significance for the design of HEMT devices. [ABSTRACT FROM AUTHOR]

This paper introduces compact Printed Ridge Gap Waveguide (PRGW) phase shifters tailored for millimeter-wave applications, with a focus on achieving wide operating bandwidth, and improved matching and phase balance compared to single-layer technology. This study proposes a unique approach to achieve the required phase shift in PRGW technology, which has not been previously explored. This study also introduces a novel analytical approach to calculate the cutoff frequency and propagation constant of the PRGW structure, a method not previously addressed. Furthermore, the utilization of multi-layer PRGW technology enables the realization of multi-layer beamforming networks without crossing, thereby supporting wideband operation in a compact size. The proposed design procedure enables the realization of various phase shift values ranging from 0 ∘ to 135 ∘ over a broad frequency bandwidth centered at 30 GHz. A 45-degree phase shifter is fabricated and tested, demonstrating a 10 GHz bandwidth (approximately 33% fractional bandwidth) from 25 GHz to 35 GHz. Throughout the operating bandwidth, the phase balance remains within 45 ± 5 ∘ , with a deep matching level of −20 dB. The proposed phase shifter exhibits desirable characteristics, such as compactness, low loss, and low dispersion, making it a suitable choice for millimeter-wave applications, including beyond 5G (B5G) and 6G wireless communications. [ABSTRACT FROM AUTHOR]

III-nitride high-electron-mobility transistors (HEMTs) are the optimal choices for high-RF and power applications due to their exceptional performance characteristics. Nevertheless, HEMTs face formidable challenges related to large gate and buffer leakage currents, which inevitably impose significant limitations on device performance and reliability. In response to these challenges, this work studies the design consideration of a T-shaped gate InAlN/AlN with polarized doped buffer HEMT. The simulation results show that the parasitic capacitances are deeply affected by the geometry of the T-gate. The less influence of gate-to-source capacitance (Cgs) by the drain voltage possesses constant depletion charges at the source side, leading to a persistent value of Cgs with drain bias. Moreover, a polarization-doped buffer layer has been incorporated, effectively enhancing the confinement of the two-dimensional electron gas by causing an upward convex bend in the conduction band. This strategic design element significantly contributes to the reduction in leakage current (10−8), positive shift of Vth (0.9 V), and improves the switching ratio (108). The effect of gate head length (Hlength), gate stem height (Sheight), and gate foot length (Flength) on various RF parameters has been investigated. The simulated results confirm that the proper choice of Hlength (280 nm), Sheight (100 nm), and Flength (10 nm) significantly reduced the parasitic capacitance (Cgs = 350 fF/mm and Cgd = 140 fF/mm) and enhanced the Fmax (840 GHz), GBP (636 GHz), Ft (583 GHz) and also improved the power gains. The extracted results of the proposed design exhibit its efficacy for high-performance RF/microwave applications. [ABSTRACT FROM AUTHOR]

For possible uses in the THz frequency range, we investigated the one-dimensional gyroidal superconductor photonic crystals in the current work. In this regard, each unit cell is designed from gyroidal Bi2Sr2CaCu2O8 (BSCCO) and SrTiO3 layers. Here, BSCCO is embedded in a hosting dielectric medium of SrTiO3 to design the gyroidal layer. The transfer matrix approach and the two-fluid model are both used in the computational analysis of the suggested structure. Studying the optical properties and investigating how several factors, including filling fraction, operating temperature, and layer thicknesses, affect the PC's performance. The results showed the emergence of the cutoff frequency at 5.35 THz. In this regard, the value of the cutoff frequency can be tuned based on the filling fraction, operating temperature, and refractive index of the hosting medium, making the structure promising for optical communication applications. [ABSTRACT FROM AUTHOR]

In this research, a one-dimensional photonic crystal with such a novel and simple design is introduced to serve as an efficient reflector for infrared (IR) wavelengths. The construction of the proposed photonic crystal design based on the gyroidal geometry is the mainstay of this research to investigate the total reflectivity through a wide band of IR wavelengths. In this regard, [Air/(A/B)10/substrate] is indeed the configuration of the suggested photonic crystal structure. The layer symbols, A and B represent two layers of silver with a gyroidal configuration in host materials of titanium dioxide and silicon, respectively. Meanwhile, our numerical findings demonstrate the existence of a cutoff feature at a wavelength of 1 μ m of the propagating electromagnetic waves. Moreover, the filling fraction of sliver through layers (A) and (B) provides a substantial role in the tunability of the cutoff frequency and the reflectivity of the structure as well. Then, we have taken into account how the host material's thicknesses and refractive indices will affect the proposed structure's reflectance. In particular, the refractive index of the host material could lead to a significant variation of the permittivities of the considered materials. Finally, we think that the proposed structure may be of a great interest in a variety of physical and engineering applications including the optical reflectors, smart windows and solar cells applications as well. [ABSTRACT FROM AUTHOR]

Polarization grading in AlGaN/GaN‐based high‐electron‐mobility transistors (HEMTs) is a promising device design option that can improve linearity, speed, power, and noise performance for use in millimeter‐wave applications. This work investigates the potential of compositionally graded HEMT heterostructures to enhance device breakdown through lateral electric field engineering while maintaining a high device cutoff frequency (fT) due to reduced longitudinal optical (LO) phonon scattering. The impact of polarization grading on electric field profile is compared with conventional gate‐integrated mini‐field plates (mini‐FPs). It is also observed that polarization grading can augment the efficacy of gate‐connected FPs, further enhancing performance. Using physics‐based 2D device simulations, it is demonstrated that polarization engineering via polarization grading enhances breakdown (VBD) while preserving high fT, resulting in a Johnson's figure of merit (JFOM = fT × VBD), that is, ≈2.4× that of a conventional abrupt‐junction HEMT. This improvement represents a significant advancement over the ≈1.25× to ≈2× increase achieved with the use of mini‐FPs alone in HEMTs. [ABSTRACT FROM AUTHOR]

This paper points out that the commonly used normalized frequency for noncircular dielectric waveguides, which is based on the semiminor axis, causes the cross‐sectional area to vary with the cross‐sectional shape. Consequently, the shape effects described with the conventional normalized frequency are not due to the shape alone but the combined effects of the shape and area. Our numerical results show that the area effect is greater than the shape effect. An improved definition of normalized frequency based on an equivalent radius is proposed in this paper. Conversion formulas to convert from the conventional normalized frequency to the proposed normalized frequency are provided for elliptical and rectangular waveguides. Our numerical results show that the shape effects described by the proposed normalized frequency are free from the area effect. Consequently, the proposed normalized frequency is more accurate than the conventional normalized frequency in describing the shape effect of noncircular dielectric waveguides. [ABSTRACT FROM AUTHOR]

This study explores the optimization of a hetero-dielectric tunnel field-effect transistor (HDTFET) structure to improve device performance. By incorporating a high-k oxide pocket in a portion of the source-side gate insulator, a local minimum in the conduction band edge is induced at the source-channel interface. This technique leads to improved tunneling rates and increased current handling capability. The simulation analysis focuses on optimizing the position and dimension of the high-k dielectric pocket to enhance key device characterization metrics such as ON-state current (ION), ON-to-OFF-state current ratio (ION/IOFF), subthreshold swing (SS), and cutoff frequency (fT). The resulting optimized design for a 30 nm-channel length involves a pocket shift of 1 nm and a pocket length of 12 nm. This configuration achieves a remarkable ON current of 55 µA/µm, which is 30 times higher than that of a conventional TFET. Importantly, other analog performance parameters remain unaffected, with fT surpassing 175 GHz for the 30 nm-channel. Additionally, transient analysis is conducted by applying a resistive load inverter circuit to a pulse input. The fall propagation delay (tphl) exhibits a greater than two orders of magnitude enhancement, along with improved overshoot voltage (VP) compared to a TFET without a pocket. The study further explores the impact of supply scaling on transient parameters. Optimal pocket scalability concerning channel length is found to be 40% for pocket length and approximately 2.5% for pocket shift relative to the source-channel interface. The proposed design significantly enhances DC and analog as well as circuit-level metrics compared to the traditional uniform gate oxide TFET.

Frequency-dependent equivalent linear (FD-EQL) site response analysis methods, developed as potential substitutes for the EQL procedure to better simulate the nonlinear soil response, have been reported to overpredict the high-frequency wave propagation. Modified procedures proposed to overcome this limitation have demonstrated to improve the fits with the nonlinear analysis results. The method has not yet been applied to perform a deconvolution analysis, where a conventional EQL analysis often fails to converge or provide reliable estimate. The conventional EQL procedure and one of the modified FD-EQL method, which uses an empirical factor f to interpolate the strain spectrum between the EQL and FD-EQL outputs, are used to perform a series of deconvolution analyses using an idealized 1000 m profile and twelve Kik-net downhole arrays. The residuals of recorded and deconvoluted motions are shown to increase with strain for the EQL method even when using the recommended frequency cut-off. For the FD-EQL method, the range of f recommended for convolution analyses is shown to provide unrealistic responses in performing deconvolution analyses. A new range that produces unbiased residuals for all strain amplitudes is proposed. Comparisons highlight that the modified FD-EQL yields reliable predictions of the within motion for all profiles and motion intensities, automatically suppressing the amplification of high-frequency noise typically accompanied in a deconvolution analysis. [ABSTRACT FROM AUTHOR]

This study explores the optimization of a hetero-dielectric tunnel field-effect transistor (HDTFET) structure to improve device performance. By incorporating a high-k oxide pocket in a portion of the source-side gate insulator, a local minimum in the conduction band edge is induced at the source-channel interface. This technique leads to improved tunneling rates and increased current handling capability. The simulation analysis focuses on optimizing the position and dimension of the high-k dielectric pocket to enhance key device characterization metrics such as ON-state current (I ON), ON-to-OFF-state current ratio (I ON / I OFF), subthreshold swing (SS), and cutoff frequency (f T). The resulting optimized design for a 30 nm-channel length involves a pocket shift of 1 nm and a pocket length of 12 nm. This configuration achieves a remarkable ON current of 55 µA/µm, which is 30 times higher than that of a conventional TFET. Importantly, other analog performance parameters remain unaffected, with f T surpassing 175 GHz for the 30 nm-channel. Additionally, transient analysis is conducted by applying a resistive load inverter circuit to a pulse input. The fall propagation delay (t phl) exhibits a greater than two orders of magnitude enhancement, along with improved overshoot voltage (V P) compared to a TFET without a pocket. The study further explores the impact of supply scaling on transient parameters. Optimal pocket scalability concerning channel length is found to be 40% for pocket length and approximately 2.5% for pocket shift relative to the source-channel interface. The proposed design significantly enhances DC and analog as well as circuit-level metrics compared to the traditional uniform gate oxide TFET. [ABSTRACT FROM AUTHOR]

Herein thin films of CrSe deposited by the thermal evaporation technique onto Pt substrates are designed as Schottky diodes. It is observed that the Pt/CrSe/C (PCC) Schottky diodes are of tunneling type showing barrier height and widths of 0.56 eV and 18 nm, respectively. These diodes displayed biasing dependent nonlinearity and negative slope of differential resistance. The analyses of the cutoff frequency spectra indicated that PCC devices can exhibit high cutoff frequency up to 17 GHz based on the driving signal frequency. The features of the PCC devices make it promising as electronic component suitable for 5G/6G technology applications. [ABSTRACT FROM AUTHOR]

This work presents the molybdenum di-sulphide three-phase bridge rectifier integrated circuit utilizing the novel self-switching diode. The self-switching diode has a planar architecture having I-V behavior similar to an ideal diode. The structure of SSD is utilized to design single phase and three phase rectifiers. The performance in terms of rectification efficiency, total harmonic distortion, ripple factor and cut-off frequency has been evaluated and compared for both single and three phase SSDBR. The three-phase self-switching diode bridge rectifier (3P-SSDBR) has a cut-off frequency of ∼400 MHz with minimum total harmonic distortion (THD) and ripple factor (RF) of 4.73% and 0.59, respectively. While, the single phase self-switching diode bridge rectifier (1P-SSDBR) has a cut-off frequency of ∼300 MHz with minimum total harmonic distortion (THD) and ripple factor (RF) of 47.86% and 1.94, respectively. Further, to validate the obtained results, the simulation models have been calibrated with experimental and theoretical findings. [ABSTRACT FROM AUTHOR]

Despite the undoubted importance of having fairly simple analytical expressions for the refractive indices of wave modes in a magnetoactive plasma, such expressions are known only in some particular cases. For electron waves with frequencies much higher than the lower hybrid resonance frequency, such an expression is known only for whistler waves in a dense plasma when the electron plasma frequency significantly exceeds the electron cyclotron frequency. In this Letter, we propose simple operational expressions for the refractive indices of all four electron modes in a magnetoactive plasma, namely, the fast magnetosonic, also called whistler mode, the slow extraordinary mode, the ordinary mode, and the fast extraordinary mode. The form of these expressions does not depend on the value of the ratio of plasma frequency to cyclotron frequency.

This paper introduces compact Printed Ridge Gap Waveguide (PRGW) phase shifters tailored for millimeter-wave applications, with a focus on achieving wide operating bandwidth, and improved matching and phase balance compared to single-layer technology. This study proposes a unique approach to achieve the required phase shift in PRGW technology, which has not been previously explored. This study also introduces a novel analytical approach to calculate the cutoff frequency and propagation constant of the PRGW structure, a method not previously addressed. Furthermore, the utilization of multi-layer PRGW technology enables the realization of multi-layer beamforming networks without crossing, thereby supporting wideband operation in a compact size. The proposed design procedure enables the realization of various phase shift values ranging from 0∘ to 135∘ over a broad frequency bandwidth centered at 30 GHz. A 45-degree phase shifter is fabricated and tested, demonstrating a 10 GHz bandwidth (approximately 33% fractional bandwidth) from 25 GHz to 35 GHz. Throughout the operating bandwidth, the phase balance remains within 45 ± 5∘, with a deep matching level of −20 dB. The proposed phase shifter exhibits desirable characteristics, such as compactness, low loss, and low dispersion, making it a suitable choice for millimeter-wave applications, including beyond 5G (B5G) and 6G wireless communications.

In this study, copper (Cu) nanosheets are utilized as semitransparent conducting optical windows for the fabrication of terahertz band filters based on chromium selenide (CrSe2). The deposition of CrSe2 thin films onto glass substrates is performed via the thermal evaporation technique followed by the application of Cu nanosheets using the ion coating technique. The interaction between Cu windows and CrSe2 films resulted in a slight widening of the energy bandgap and a remarkable reduction in the Urbach tail states from 2.24 to 1.23 eV. Furthermore, the coating of CrSe2 with Cu optical windows led to a decrease in the dielectric constant values of more than 35% and an increase in the terahertz cutoff frequency by more than 70%. The application of Cu windows increased the cutoff frequency to 23 THz. The correlation between electrical and optical conduction in the terahertz band filters is investigated through the utilization of Drude–Lorentz models, revealing that although Cu windows reduced the free carrier density and conductivity, they enhanced drift mobility, resulting in more efficient terahertz filter properties. The calculated optical constants and optical conductivity parameters provided evidence of the suitability of Cu‐coated CrSe2 films for applications in terahertz technology. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate and explore the optical properties of one-dimensional ternary photonic crystal design containing graphene layers. By using the well-known transfer matrix method, the optical properties of the proposed designs are investigated at the terahertz (THz) region. The numerical results show the appearance of cutoff frequency feature within THz range. We found that the cutoff frequency feature is tunable through the considered spectrum by controlling the design parameters such as the thicknesses of the constituent materials and the incident angle of the incident light. Also, the results show that the chemical potential and the temperature of the graphene optical conductivity have a significant effect on the cutoff frequency. Finally, by using non-linear regression analysis, we fit our results to a quadratic regression model. Accordingly, a cutoff frequency of interest can be selected in a straight-forward way through the THz region. The proposed design can be useful in many applications at the THz region such as band-pass filters, high reflection mirrors, fibers, and microcavities. [ABSTRACT FROM AUTHOR]

To accurately determine the strength and the waveform of the partial discharge (PD) signal, especially if the source position is far from the ultra-high frequency (UHF) sensor or if the signal is weak, it is necessary to properly extract the most prominent PD from the background noise in the recorded signal. This paper provides a new procedure for the extraction of PD signal in the predominant very high frequency (VHF) range from the strong noise in each of the signals recorded online and onsite using the UHF sensor in the power transformer during its normal operation in a thermal power plant. A standard UHF drain valve sensor was used with good sensitivity in the high frequency and VHF bands. First, it is necessary to determine as precisely as possible the period in which the most prominent PD occurs in the middle part of each signal. Second, it is to compare the frequency spectra of the dominant, strong noise in the left and right parts in relation to the corresponding middle part of each recorded signal. And third, it is to extract the PD with the largest amplitudes from the estimated noise in the middle part of each recorded signal by finding the cutoff frequency and performing high-pass filtering in MATLAB. The new criterion for cutoff frequency is that there are no time shifts of the first peaks of the most prominent PD of each recorded signal. The results show some obvious similarities of PDs in the recorded signals, such as frequency range, duration, repetition rate, and the same dominant frequency, which sufficiently indicates that it is the same type of PD. [ABSTRACT FROM AUTHOR]

In this paper, the system of equations for nonlocal micropolar elastic materials is developed taking into account the assumption that the attenuation functions for the elastic and micropolar material coefficients are different, and applied for harmonic body waves. The dispersion equations of harmonic body waves propagating in a micropolar medium and their cutoff frequencies are obtained in simple form based on the new assumption. The obtained dispersion relations are potentially useful in an inverse problem by fitting the data of elastic and micropolar harmonic waves speed to estimate the elastic and micropolar nonlocal parameters of the medium. Some concerning remarks about the difference between the two-parameter nonlocal theory and the one-parameter nonlocal theory of Eringen are numerically discussed to show the necessary of the developed theory in the problem of wave propagation. [ABSTRACT FROM AUTHOR]

To increase the spatial resolution of passive microwave radiometry, mirrored aperture synthesis (MAS) was presented. In this letter, the method of cosine visibility extension (CVE) is proposed to further enhance the spatial resolution of 1-D MAS. In the CVE method, a convolutional neural network (CNN) is used to learn the distribution of the cosine visibility (CV), specifically the relationship between the low- and high-frequency CV distributions of various scenes. Then, the high-frequency CVs are estimated by the CNN according to the low-frequency CVs obtained by MAS. The high- and low-frequency CVs are combined in MAS image reconstruction to enhance the spatial resolution of MAS. The simulation and experiment indicate that the CVE method can effectively enhance the spatial resolution of MAS. [ABSTRACT FROM AUTHOR]

In Junctionless transistors, the source-channel-drain doping is of the same type and level, hence, the process of making Junctionless transistors is easier than inverting mode transistor. Despite this benefit, reducing the transconductance of Junctionless transistors due to reduced carrier velocity makes the operation of this type of transistor difficult for analog, radio frequency and high frequency noise usages. An effective method that increases the trans-conductance of Junctionless transistors without reducing efficiency is using a heterogeneous structure in the channel. In the present article, using Si and Si1-xGex materials in the channel is proposed and modeled so as to enhance the transconductance of Junctionless transistor. The special structure of the proposed transistor, called JL-Si / Si1-xGex, eliminates the intervalley scattering between valleys of ∆2 and ∆4. This increases the velocity of the electron and consequently enhances the transconductance. The outcomes of the modelling of the proposed JL-Si / Si1-xGex heterostructure transistor indicate the maximum transconductance of 2.5 mS / um, which increases 50% compared to similar silicon transistor. Moreover, calculations which are extracted from modelling demonstrate that the proposed JL-Si / Si1-xGex transistor has a unity gain cutoff frequency of 750 GHz, minimum noise figure of 65.0 dB, and an available gain of 28.5 dB. The parameters of cut-off frequency, minimum noise figure and available gain of the proposed JL-Si / Si1-xGex transistor have been improved by 34%, 62.5% and 53%, respectively, compared to the JL-Si transistor with similar dimensions. The proposed device can be suitable candidate for RFIC applications.

Subject and Purpose. The InN Gunn diode is known as the device capable of generating powerful oscillations atfrequencies above 300 GHz. A possible way for increasing both the microwave power and the cutoff frequency of the Gunn diode is to employ graded-gap semiconductors. The subject of this research is the process for generating electrical oscillations in InN and graded-gap GaInN Gunn diodes that involve resistive contacts at the cathode and the anode, and possess a 1-μm long active region. The research is aimed at suggesting an optimized structure for the graded-gap GaInN diode to obtain a maximum microwave power and maximum frequency of the oscillations, while consuming the lowest possible amount of DC power. Methods and Methodology. А hydrodynamic simulation has been performed of transport of electrons in graded-gap semiconductors, and an integro-differential equation analyzed concerning voltage drop across elements of the related RLC circuit. Results.The power spectra of oscillations have been analyzed for a variety of parameters of both the Gunn diode and the RLC circuit. The frequency dependences of the oscillatory power, characteristic of different electron concentrations, provide evidence for the possibility of obtaining considerable microwave powers at frequencies above 300 GHz through the use of graded-gap GaInN diodes. Conclusion. The results that have been obtained clearly confirm the expected practicality of using a graded GaInN layer in the InN diode for increasing the power of microwave oscillations, reducing the necessary level of the DC power, and restraining the dependence of the output characteristics on the electron density. The highest power of oscillations has been demonstrated by the InN diode with a 0.1 µm long graded-gap layer of GaInN. Meanwhile, the oscillation frequency generated in that diode is somewhat lower than in the InN diode. A compromise between the values of generated power and the oscillation frequency has been reached in the diode with a graded-gap GaInN layer of 0.9 µm in length. In addition, the latter structure requires the lowest level of DC power for effectuating microwave generation at the higher feasible frequencies.

Organic electrochemical transistors (OECT) are gaining momentum in future applications of biosensors and bioelectronics. Nonetheless, contact (or series) resistances (RS/D) remain underexplored, even though physical processes between the source/drain electrodes and organic mixed ionic‐electron conductors (OMIECs) drive a substantial part of their performances. To address this shortcoming, in this study, low‐dimension OECTs featuring 2 µm‐long poly(3,4‐ethylenedioxythiophene) and polystyrene sulfonate acid (PEDOT:PSS) channel are explored. Normalized contact resistances (RS/D⋅W) values as low as 1.4 W cm are obtained. It is observed that channel PEDOT:PSS thickness is not detrimental to RS/D but is impacting the cut‐off frequency. A figure‐of‐merit (h) expressing the charge‐carrier injection (or extraction, respectively) efficiency shows that planar depletion‐mode OECTs are not contact‐limited up to L = 30 µm channel length. Finally, an unprecedented approach that highlight the importance of optimizing the micro‐fabrication technologies is shown, by decreasing the contact overlap length, according to OMIECs physicochemical contact properties. Indeed, a transfer‐length method coupled to a current‐crowding model allow to fully understand the behavior of low‐dimension PEDOT:PSS OECTs and next, to optimize its circuits design. This is paving the way toward the development of OECTs‐based integrated circuits with faster switching speed, broadening further their scopes and future use as advanced bioelectronics platforms. [ABSTRACT FROM AUTHOR]

This paper presents the structure and techniques for frequency compensation of the floating load voltage‐controlled current sources employing power operational amplifiers (op‐amps), as active building blocks. Based on the performed theoretical analysis, conditions for self‐oscillation are determined, and an approach for introducing frequency compensation in a predetermined bandwidth is proposed. The obtained analytical expressions, as well as some additional conditions, are the basis of the proposed design procedure. The practical applicability of the proposed procedure has been tested by designing and analyzing sample electronic circuits of floating load voltage‐to‐current converters. [ABSTRACT FROM AUTHOR]

In this paper, the transmission characteristics, of an asymmetric periodic structure of air/LHP‐MCP is considered as LHPPC, are determined. In this study, the same structure with symmetrically introduced defect layer of MCP, as (AB)N/2B(BA)N/2, under same configuration is also analyzed. The authors find that, with an increase in magnitude of magnetizing field, the transmittance in such PCs increase. The transmittance in defect‐introduced PC is low as compared to corresponding LHPPC without defect. It is investigated that the cutoff value of frequency (GHz) for transmission for the defective LHPPC decreases with an increase in magnetic field similar to those of the PC without defect. Here, the complete bandgap obtained at a higher frequency range in the spectra of the defective PC exhibits defect mode and disappears at B = −0.8T, which is disappearing at B = −0.6T in case of the PC without defect. It is demonstrated that both the PCs show broadband reflector behaviors at lower frequency range with low magnetic field, viz. B = −0.2T, while the impact of defect is to further reduce the transmission in MCP‐based PC, for chosen values of the magnetic field. The obtained results under this analysis may be referred in designing broadband reflectors as well as multichannel transmitters and high transmitter with low and high magnetic fields, respectively. The shifting in the cutoff frequency for transmission with magnetic field shows the applications of such PCs in switching devices. [ABSTRACT FROM AUTHOR]

The scientific and practical significance of the synthesis of demodulators in solving the problem of monitoring unknown radio emissions has been substantiated. Features of the photoelastic effect are discussed in the context of constructing an amplitude demodulator. A mathematical model of the signal generation process at the output of the demodulator has been developed. It is shown that the output signal of this model is a copy of the information contained in the radio signal at the input of demodulator. In this case, the amplitude demodulator also performs the function of a low-pass filter with a characteristic cutoff frequency. A method for calculating the demodulator cutoff frequency based on the transient response is proposed. A breadboard of acousto-optic amplitude demodulator based on Bragg's cell with the central frequency of 80 MHz has been created. A number of experimental studies were conducted to verify the established concepts. The demodulation processes of signals with amplitude and pulse modulation were considered. It has been proved by experiment that the acousto-optic amplitude demodulator reproduces information with accuracy sufficient for practice. An example of determining the cutoff frequency of acousto-optic amplitude demodulator by employing the shape of the output pulse is presented. [ABSTRACT FROM AUTHOR]

Several applications of a cylindrical waveguide filled with inhomogeneous materials have been demonstrated. Analytical solutions for modes, an inhomogeneous cylindrical waveguide, are available only for a few material parameters and those are also mostly approximations. We have obtained exact analytical solutions for cylindrical waveguides filled with different inhomogeneous and anisotropic material parameters. Different sets of material parameters are obtained using the geometric transformation method. The analytical and numerical modal field distributions, the value of cutoff frequencies and effective mode indices for different propagating modes are well matched to each other. The inhomogeneity can be used to miniaturize the radial dimensions of the waveguide. This is highly desirable for many applications like sensing, near-field coupling and magnetic resonance imaging (MRI). [ABSTRACT FROM AUTHOR]

Abstract Organic electrochemical transistors (OECT) are gaining momentum in future applications of biosensors and bioelectronics. Nonetheless, contact (or series) resistances (RS/D) remain underexplored, even though physical processes between the source/drain electrodes and organic mixed ionic‐electron conductors (OMIECs) drive a substantial part of their performances. To address this shortcoming, in this study, low‐dimension OECTs featuring 2 µm‐long poly(3,4‐ethylenedioxythiophene) and polystyrene sulfonate acid (PEDOT:PSS) channel are explored. Normalized contact resistances (RS/D⋅W) values as low as 1.4 W cm are obtained. It is observed that channel PEDOT:PSS thickness is not detrimental to RS/D but is impacting the cut‐off frequency. A figure‐of‐merit (h) expressing the charge‐carrier injection (or extraction, respectively) efficiency shows that planar depletion‐mode OECTs are not contact‐limited up to L = 30 µm channel length. Finally, an unprecedented approach that highlight the importance of optimizing the micro‐fabrication technologies is shown, by decreasing the contact overlap length, according to OMIECs physicochemical contact properties. Indeed, a transfer‐length method coupled to a current‐crowding model allow to fully understand the behavior of low‐dimension PEDOT:PSS OECTs and next, to optimize its circuits design. This is paving the way toward the development of OECTs‐based integrated circuits with faster switching speed, broadening further their scopes and future use as advanced bioelectronics platforms.

Battery-less wireless sensor networks (BL-WSNs) are an interesting and sustainable solution for Internet-of-Things (IoT) applications. The sensor nodes in the BL-WSNs are often powered by an energy harvester. Generally, these harvesters provide intermittent energy to the BL-WSNs. Hence, to cater to a variety of applications, the energy harvesters should work as a high-pass filter, that is, provide continuous energy to the BLWSNs. This article proposes a novel design to harvest vibration energy using a coupled Dovetail-shaped piezoelectric and electromagnetic energy harvester (Dovetail-PEM-EH). Unlike earlier PEM-EH designs with either one or two vertical cantilevers, Dovetail-PEM-EH uses three bimorphs and one copper (fixed tip end) cantilever with magnets on the tips. Placing more than two cantilevers with tip magnets requires optimizing distances among cantilevers and selecting tip magnets in such a way that energy harvesting is increased and the design is stable, that is, cantilevers do not collide with each other. A low-complexity binary search-based algorithm is presented to achieve the same. By doing so, the magnetic attractive forces increase the vibration sensitivity of the proposed design, and it works as a high-pass mechanical filter with a low cutoff frequency. The detailed simulation analysis performed in COMSOL shows that there is a minimum $2\times $ increase in the voltage and six out of the nine tested models show more than $3\times $ improvement in the harvested power when compared to the state-of-the-art. The hardware implementation of one of the models validates the simulation results with a slight variation. [ABSTRACT FROM AUTHOR]

The frequency-dependent signal-to-noise ratio of terahertz time-domain signals is a relevant source of uncertainty for parameters measured with it. It also limits the total usable bandwidth of such signals. In the great majority of cases, the processes to establish the limits of this usable bandwidth are determined based on the experience of the user. Therefore, it is desirable to develop a procedure to automate this calculation. In this work, a method to estimate the bandwidth of terahertz time-domain signals is presented. Different spectra were analyzed, showing the potential of the algorithm in the calculation of cutoff frequencies which delimits the usable bandwidth. [ABSTRACT FROM AUTHOR]

In this brief, a design of microstrip lowpass filter with the 1 GHz cutoff frequency is revisited, where a class of modified Jacobi polynomials is used for the filter design. The optimization procedure for these filters includes the passband return loss minimization and the roll-off factor enhancement using the magnitude correction of the transmission coefficient. Mentioned correction is performed by introducing the multiple transmission zeros such that LC ladder prototype filter can be realized symmetrically. Three seventh degree filters for L-band applications are realized and simulated: allpole, with a single and double transmission zeros. It is shown that, among these three stepped impedance lowpass filters realizations, the filter with simple transmission zeros offers the best performance. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Beijing University of Technology is the property of Journal of Beijing University of Technology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To overcome the nonlinear distortion inherent in analog ICs based on Si-MOSFETs, we report here the graphene-silicon hybrid analog amplifier ICs that integrate graphene field-effect transistor (GFET) and Si-MOSFET components. By fabricating homogeneous GFETs on a silicon wafer with prefabricated Si-MOSFETs, we obtained the hybrid ICs that neatly incorporate the high linearity of GFETs. The high-linearity analog amplifier ICs can thus be realized simply using basic MOSFET circuit configurations, without requiring complicated calibration designs. This hybrid integration principle may enable immediate practical applications of graphene electronics. [ABSTRACT FROM AUTHOR]

In this brief, a high-speed wideband track-and-hold amplifier (THA) is implemented in a $0.8~{\mu }\text{m}$ InP double-heterojunction bipolar transistor (DHBT) process. This THA is based on a base-collector (b-c) switching diode architecture and achieves a −3 dB bandwidth of 35 GHz at a sampling rate of 30 GSa/s. For the first time, an enhanced unity-gain frequency (${f_{T}}$) doubler and an active peaking technique are used together in the design of the b-c switching diode sampler. The dominant pole of the THA is canceled by one zero produced by the active peaking structure. This is one step to improve the bandwidth. Secondly, the enhanced ${f_{T}}$ -doubler structure improves the driving capability of the input buffer at high frequencies. Therefore, the bandwidth of the THA is further extended. The measurement results show a total harmonic distortion (THD) of <−30.0 dBc and a maximum spurious-free dynamic range (SFDR) of 47.07 dB at a 30-GSa/s sampling rate. S-parameter tests show a better than −43 dB isolation within 45 GHz in hold-mode, and a −3 dB bandwidth of 35 GHz in track-mode under a 165 GHz device ${f_{T}}$. The proposed THA has the potential for high-speed broadband applications due to its competitive performance. [ABSTRACT FROM AUTHOR]

Copyright of Laser Technology is the property of Gai Kan Bian Wei Hui and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this article, we exhibit an order reduction output-feedback attitude stabilization scheme for 2-degree-of-freedom (2-DOF) helicopters by considering system nonlinearity and parameter variations in the controller and observer design tasks. As the first merit, the proposed observer for the angular velocity contains the disturbance estimation mechanism as a subsystem assisting the main estimator, which is independent of the system parameter information. As the second advantage, the resultant observer renders it possible to design an improved proportional-derivative-type controller that includes the active damping term and nonlinearly structured design parameters, reducing the closed-loop system order to 1. The Quanser 2-DOF helicopter system experimentally validates the practical merit of the proposed technique. [ABSTRACT FROM AUTHOR]

This paper presents experimental RF characterizations and modeling on the nano-scale multi-finger gate MOSFETs of the HLMC 40 nm low-power CMOS technology. Both the resistive and capacitive components in the equivalent circuit model for the RF MOSFET devices are calibrated based on temperature-dependent S-parameter measurements (0.25 – 40 GHz) from 298 K to 6 K. By integrating the intrinsic device model and the extrinsic parasitic parameters, a generic cryogenic device RF model is developed to capture the cutoff frequency and high-frequency performance of NMOS and PMOS transistors with varied device configurations. The establishment of validated database as functions of device size, temperature, and frequency responses lays a solid foundation for practical large-scale cryo-CMOS RF circuit design and optimization.

This work demonstrates the high-frequency characteristics of In0.53Ga0.47As nanowire with scaled wire width by implementing TCAD simulations. The physical models and correlated parameters have been calibrated to the experiments (Ko et al., 2022). As the width of the nanowire is scaled to 10 nm, the electron density peaks are no longer located close to the oxide/semiconductor interface. Instead, the peaks merge and volume inversion effects appear due to the strong quantum confinement. The volume inversion effects lead to higher cut-off frequency due to the reduced total transport delay time. To have a better understanding of this phenomena, the high-frequency properties of nanowire were quantified with the assistance of small-signal analysis and delay time analysis using TCAD. It is found that the channel charging delay increases with narrower wire width due to the raise of source/drain resistance. Regarding the extrinsic and intrinsic delay, they increase with smaller wire width and drop at width of 10 nm due to the volume inversion effects. Electron distribution which aims to clarify the above-mentioned observation is also plotted.

• We have proposed new formulas for analyzing and calculating the intrinsic dynamic resistance, gain, and cutoff frequency of double heterojunction bipolar transistors. • The reliability of our physics-based model through comparisons with experimental reports from three different research institutions. • Our work also introduces a novel method for obtaining the equivalent circuit of a transistor, providing an effective way to analyze various quantitative performance limiting factors. This can be extremely useful for designing and optimizing transistors. Significant discrepancies were found between experimental results and the results calculated by the conventional physics-based model for the cutoff frequency and some equivalent circuit parameters of double heterojunction bipolar transistors (DHBT). In order to accurately evaluate the primary quantitative performance of DHBT, a comprehensive physics-based model was developed and validated by comparing experimental data from three research institutions. The proposed physics-based model combines the equivalent circuit of the T-topology and hybrid-π topology, and includes modification formulas for estimating the intrinsic dynamic resistance of the base–collector and base-emitter junctions, as well as the cutoff frequency, the hybrid-π input capacitance, and the gain. [ABSTRACT FROM AUTHOR]

The rigorous solution for the single floating pile in layered soil subjected to lateral dynamic loads acting on the pile head is proposed. A unified depth-dependent soil mode function is systematically constructed using the matrix transfer method to ensure layer interface continuity. The model captures the pile head compliance comprehensively, encompassing swaying, rocking and cross-swaying-rocking compliance components. The model is validated by comparing with the existing solutions. The cutoff frequency for each mode is obtained explicitly and is captured by the present model. Parametric studies show that the cutoff frequency for the pile head swaying compliance component reaches the maximum value corresponding to each order of the cutoff frequency. The swaying compliance is affected significantly by the properties of the shallow layer, but its effect on the rocking-associated compliance components is limited. Furthermore, the horizontal displacement of the pile–soil system develops deeper and broader when the stratum becomes softer. The soil displacement attenuates rapidly with the distance to the pile and dissipates when it exceeds 20 times the pile diameter. [ABSTRACT FROM AUTHOR]