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Distributed Small-signal Equivalent Circuit Model and Parameter Extraction for SiGe HBT
摘要： In this paper, we present an improved high frequency small-signal distributed model for SiGe HBTs under forward-active mode based on the transmission line theory. The distributed nature of the transistor structure is taken into account in the proposed model. The single SiGe HBT is considered to be a cascade of many infinitesimal transistors, connected with the intrinsic base resistance. The closed-form solutions of admittance parameters for the distributed model are derived by solving the transmission line equation. With reasonable approximation and simplification, the model parameters are then directly extracted based on the nonlinear rational function fitting. The new improved distributed model and parameter extraction technique are validated with a 1×1.2×30 μm2 SiGe HBT from 100 MHz to 20.89 GHz. The simulated S-parameters in the proposed transmission line model are in close agreement with the measured data, and the frequency characteristics of the transistors are well predicted.
关键词： parameter extraction,rational function fitting,transmission line,SiGe HBT,Device modeling,small-signal model
更新于2025-09-23 15:23:52
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Uncertainty analysis for ac–dc difference measurements with the AC Josephson voltage standard
摘要： A detailed analysis of the uncertainties obtained in ac–dc difference measurements with an AC Josephson voltage standard (ACJVS) is presented. For audio frequencies and for voltages less than 200 mV, ac–dc transfers with the ACJVS may reduce the combined uncertainty by factors of 2–10, compared with conventional methods based on thermal converters. Type A uncertainties are predominantly limited by the thermal transfer standard (TTS), or the digital voltmeter used to acquire the output voltage from the TTS. In agreement with earlier work, the transmission line is the primary contributor to Type B errors for frequencies above 10 kHz. A Monte Carlo sensitivity analysis is used to demonstrate how the uncertainties of transmission line impedance and on-chip inductance impact the accuracy of the rms amplitude conveyed to the TTS.
关键词： ac voltage metrology,transmission line analysis,Josephson junction arrays,quantum voltage standards,uncertainty analysis
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Wide-Angle Frequent Scanning Metamaterial Leaky Wave Antenna Array for Automotive Radars
摘要： This paper designs a wide-angle frequency scanning metamaterial (MTM) leaky wave antenna (LWA) array for automotive radars. The gap capacitors and the vialess open stub-loaded resonators are used to construct the frequency scanning MTM LWA array. The propagation constant of the MTM LWA array is able to change from negative to positive values as the frequency is increased, resulting in backward to forward beam scanning. Compared to mechanical beam scanning arrays and phased arrays, the frequency scanning MTM LWA arrays have advantages of reducing the system complexity, light weight and low cost. The presented MTM LWA array has a maximum gain of 13 dB and wide scanning angle from -60° to +80° as the frequency varies from 23.5 to 25.6 GHz which is well suited for automotive radar applications.
关键词： frequency scanning antenna,composite right/left-handed transmission line,Antenna array,metamaterial,leaky wave antenna
更新于2025-09-23 15:22:29
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DESIGN OF DUAL- AND QUAD-BAND E-CRLH-TLS WITH ARBITRARY PHASE CHARACTERISTICS
摘要： In this paper, extended composite right/left-handed (E-CRLH) transmission line (TL) metamaterial structures, with two left-handed (backward) and two right-handed (forward) pass bands, are investigated. Also, design procedures in order to design dual- and quad-band E-CRLH-TLs are presented in detail and the parameters of these structures are extracted by clean formulas, while satisfying arbitrary phase shifts at the operating frequencies. Finally, the dispersion and characteristic impedances of these transmission lines are derived and plotted. The results of this paper can be applied to any type of TL-based dual- and quad-band microwave component.
关键词： microwave component,metamaterial,phase shift,dual-band,E-CRLH,quad-band,transmission line
更新于2025-09-23 15:22:29
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Impact Analysis of DSSC on Distance Relay Performance under Fault Conditions
摘要： This paper demonstrates the impact analysis of the Distributed Static Series Compensator (DSSC), on the performance of distance relay protection of high voltage transmission lines. The concept of DSSC model with its control circuit and distance relay are described. A five bus test system with DSSC and distance relay is designed with the help of MATLAB/SIMULINK software. The impact of DSSC on distance protection relay for different fault conditions and various fault locations is analyzed. The results of simulation show that the connection of DSSC in the transmission system changes the transmission line impedance greatly as estimated by the distance relay to be less or greater than the actual impedance in fault conditions. Hence, the distance relay performance changes, either over reaches or under reaches.
关键词： FACTS Controller,Distributed FACTS Devices,Distributed Static Series Compensator,High Voltage Transmission Line,Distance Relay
更新于2025-09-23 15:22:29
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Modal transmission line theory of plane wave excited layered media with multiple conductive anisotropic sheets at the interfaces
摘要： A succinct and efficient transmission line formulation is presented for the analysis of plane wave excited planar multilayered uniaxial media comprising multiple conductive sheets at the interfaces. The conductive sheets may be anisotropic with a fully populated conductivity tensor, which results in the coupling the transverse-magnetic and transverse-electric waves. The transmission line formalism is thus extended to accommodate this hybrid mode of propagation. Three different algorithms for the solution of the transmission line network are developed and compared, including a numerically stable and efficient scattering matrix procedure. Numerical examples are included that validate the theoretical method.
关键词： Anisotropic conductive sheet,Terahertz,Transmission line network,Transition matrix,Graphene,Scattering matrix,Plane wave,Planar multilayer
更新于2025-09-23 15:22:29
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Modeling and Simulation of Comprehensive Diode Behavior under Electrostatic Discharge Stresses
摘要： Diodes are effective devices for Electrostatic Discharge (ESD) protection. To accurately predict ESD robustness through circuit simulation of protection architectures in integrated circuits that use diodes, an enhanced model is proposed. This model is constructed with several compact model elements to simulate all physical device behaviors under high current transient ESD conditions, namely voltage overshoot, on-resistance variation, and thermal failure. The proposed model implements a thermal monitor, which can not only correlate current – voltage characteristics with the self-heating effect, but accurately predicts thermal failure under different pulse width conditions. The simulation results of this comprehensive diode model benchmarked against measurements are also reported.
关键词： junction thermal failure,Electrostatic discharge (ESD),thermal network,transmission line pulse (TLP),on-resistance variation,overshoot
更新于2025-09-23 15:21:21
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Low-Terahertz Transparent Graphene-Based Absorber
摘要： A new, transparent, metal-free absorber, based on the use of multilayer graphene/dielectric laminates (GLs), is proposed for applications in the low-terahertz frequency range. The designed absorber has a total thickness of around 70 μm and consists of a front matching dielectric layer followed by a GL, a dielectric spacer and a back GL. The laminates are periodic structures constituted of graphene sheets separated by 50-nm-thick polyethylene terephthalate (PET) interlayers, while the matching layer and the spacer are one-quarter-wavelength thick and made of PET. The GLs are modeled as homogeneous-equivalent single layers (ESLs) characterized by their sheet resistances Rs. An innovative analytical method is proposed in order to select Rs values optimizing the electromagnetic wave absorption either in low-gigahertz or low-terahertz frequency range. The frequency spectra of the absorption, reflection and transmission coefficients are computed in the range up to 4 THz by using different values of Rs. Then, realistic Rs values of chemically doped graphene monolayers over PET substrates are considered. The designed absorbers are characterized by an absorption coefficient with a peak value of about 0.8 at the first resonant frequency of 1.1 THz, and a 1.4 THz bandwidth centered at 1.5 THz with reflection coefficient below - 10 dB. Moreover, the optical transmittance of the proposed absorbers are computed by means of the optical matrix theory and it is found to be greater than 86% in all the visible ranges.
关键词： absorption,reflection and transmission performance up to 4 THz,low-terahertz transparent absorber,transmission line approach,graphene-polyethylene terephthalate laminate,laminate effective medium model,optical transmittance in the visible range
更新于2025-09-23 15:21:01
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[IEEE 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Guangzhou, China (2019.5.19-2019.5.22)] 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Compact Cross-coupled Quarter-mode SIW Bandpass Filters with Different Locations of Input and Output Ports
摘要： We propose an effective approach for optimal wideband cloaking of objects with arbitrary shapes exploiting adjoint sensitivity analysis. Our method optimizes the voxel-by-voxel constitutive parameters of an anisotropic cloak resulting in a large number of optimizable parameters. The associated sensitivities of a wideband cloaking objective function are efficiently estimated using our in-house anisotropic adjoint variable method (AVM) simulator. Only one adjoint simulation is needed regardless of the number of required sensitivities. A gradient-based optimization algorithm utilizes the available sensitivity information to iteratively improve the wideband cloaking objective function and to determine the constitutive parameters of the optimal cloak.
关键词： optimization,transmission line matrix (TLM) method,cloaking,Adjoint variable method (AVM)
更新于2025-09-23 15:21:01
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Tunable Terahertz Graphene-Based Absorber Design Method Based on a Circuit Model Approach
摘要： In this paper, a simple, fast, and novel method for designing a tunable terahertz absorber with arbitrary central frequency and desired fractional bandwidth is presented. The proposed absorber consists of a single layer periodic array of graphene ribbons (PAGRs), placed a quarter wavelength from a metallic ground, separated by a dielectric material. An analytical circuit model of the terahertz absorber is used to obtain analytical expressions for the input impedance of the proposed device. Then, a simple expression for determining the value of capacitance and the resonance conditions of the RLC circuit is used to achieve a terahertz absorber with arbitrary central frequency and desired fractional bandwidth. The proposed method is applicable for the design of both narrowband and broadband absorbers, with only one layer of graphene ribbons. Also, the presented method is applicable for designing ultra-wideband absorbers using multiple layered PAGRs. Full-wave numerical simulation is performed to verify the accuracy and validity of the presented method. Excellent performance of the proposed method in terms of computation time and memory resource and providing the desired terahertz absorber characteristics shows that our method is promising as a design approach for sensing, imaging and ?ltering applications.
关键词： circuit model,graphene,Terahertz absorber,transmission line method,tunable bandwidth
更新于2025-09-23 15:21:01