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An efficient blind calibration method for nonlinearity mis-matches in <i>M</i>-channel TIADCs
摘要： As gain, offset, and timing mismatches, nonlinearity mismatches also contribute to spurious components which deteriorate TIADC’s performance. This paper proposes an efficient blind calibration method for nonlinearity mismatches in M-channel TIADCs. A modified model for nonlinearity mismatches is established by exploiting binary Hadamard transform (BHT) and differentiator. The calibration is composed of two stages—mismatches compensation and coefficients identification. The principle of mismatches compensation is to reconstruct estimations of the mismatches-induced spurious components and subtract them from the original TIADC’s output. The coefficients identification is performed based on filtered-x least mean square (FxLMS) algorithm. By using improved model and calibration algorithm, the proposed method consumes less computational resource according to the complexity comparison. To tackle the 4-order nonlinearity mismatches in an 16-channel TIADC, the proposed method consumes 23% fewer multipliers than the previous work. Simulation results reveal that both effective resolution and dynamic range improve a lot after calibration.
关键词： frequency-dependent nonlinearity mismatches,TIADC,filtered-x least mean square,binary Hadamard transform,differentiator
更新于2025-09-23 15:23:52
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Inserting a Low-Refractive-Index Dielectric Rear Reflector into PERC Cells: Challenges and Opportunities
摘要： Light emitting devices based on Si quantum dots/SiO2 multilayers with dot size of 2.5 nm have been prepared. Bright white light emission is achieved under the dc driving conditions and the turn-on voltage of the device is as low as 5 V. The frequency-dependent electroluminescence intensity was observed under ac conditions of square and sinusoidal wave. It was found that the emission wavelength changes with frequency when sinusoidal ac is applied. The degradation of emission intensity is less than 12% after 3 h for ac driving condition, exhibiting the better device stability compared to the dc driving one.
关键词： electroluminescence (EL),Direct current (dc),Si quantum dots (Si QDs),frequency dependent
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Sozopol, Bulgaria (2019.9.6-2019.9.8)] 2019 IEEE 8th International Conference on Advanced Optoelectronics and Lasers (CAOL) - Evaluation of Unauthorization at the Express-Control of Heating of Natural Gas
摘要： Light emitting devices based on Si quantum dots/SiO2 multilayers with dot size of 2.5 nm have been prepared. Bright white light emission is achieved under the dc driving conditions and the turn-on voltage of the device is as low as 5 V. The frequency-dependent electroluminescence intensity was observed under ac conditions of square and sinusoidal wave. It was found that the emission wavelength changes with frequency when sinusoidal ac is applied. The degradation of emission intensity is less than 12% after 3 h for ac driving condition, exhibiting the better device stability compared to the dc driving one.
关键词： electroluminescence (EL),Direct current (dc),Si quantum dots (Si QDs),frequency dependent
更新于2025-09-23 15:21:01
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Frequency-dependent equivalent modelling of broadband air-coupled transducers
摘要： Electrical impedance is an essential parameter for characterizing the performance of transducers during manufacturing and application phases. The Conventional method to model the electrical impedance is based on Butterworth-Van Dyke (BVD) model with constant equivalent parameters, which is valid only in the neighborhood of resonance frequency. In this study, we present a method for modelling the electrical impedance over broadband featuring improved BVD model with frequency-dependent equivalent parameters. In order to obtain frequency-dependent parameters from the measured impedance, estimation is performed in a constrained piecewise and stepwise manner. Firstly, a concise calculation method to obtain initial values of equivalent parameters is presented. Then, the original impedance is equally divided into multiple segments and the resonant segments containing the resonant frequencies are located. New impedance data is reconstructed with one of non-resonant segments and the resonant segments. Finally, with the initial values refined by genetic algorithm (GA), equivalent parameters are obtained from the reconstructed impedance based on GA. The estimation results are assigned to the central frequency point of the non-resonant segment. A new segment is generated by shifting the last non-resonant segment one frequency interval, and data reconstruction and estimation process are repeated till all parameters at each frequency are gained. Frequency-dependent parameters are obtained by the combination of a series of constant parameters at each frequency. The proposed method is verified with good accuracy in modelling of electrical impedance and transmitting response of broadband air-coupled transducer used for gas flow measurement which are difficult to be accurately modelled by the traditional method.
关键词： Electrical impedance,frequency-dependent parameters,improved BVD model,broadband air-coupled transducers
更新于2025-09-23 15:19:57
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[IEEE 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - Rome, Italy (2019.6.17-2019.6.20)] 2019 PhotonIcs & Electromagnetics Research Symposium - Spring (PIERS-Spring) - A GaAs Integrated Power Divider Based on Microstrip and LC Structure with Optimized Capacitance
摘要： In this paper, a microstrip LC two-section Wilkinson power divider based on GaAs IPD process is proposed. A method on adjusting circuit parameters is demonstrated, which can compensate the parasitic e?ects of frequency-dependent passive components. One of the sections is a lumped LC network and the other section consists of microstrip lines. This design can reduce the size of the power divider and avoid a high loss. The inductance and capacitance of this power divider are calculated to ensure that the LC network is equivalent to a microstrip line. However, the capacitances and inductances are all sensitive to frequency so there is a signi?cant variation among calculation with ideal components and simulation with practical models. To solve this problem, even-mode input admittance is studied. By plotting a polar diagram of ideal and simulated even-mode input admittances, it is clear that a di?erence exists among simulation and ideal target, which causes the performance degeneration. This polar diagram also indicates a method on optimizing the admittance by increasing capacitance in the LC network. Increased capacitances are utilized in power divider simulation. Simulated results are compared and an optimized capacitance, which guides our ?nal design, is obtained. This power divider is fabricated using GaAs IPD process and measured on wafer. Measurement agrees well with simulation: operation band is 2.850 GHz to 4.832 GHz. A 1.982 GHz bandwidth is achieved. The insertion loss of port 2, 3 is less than 1.30 dB in this frequency range, and the isolation is higher than 18.5 dB.
关键词： frequency-dependent passive components,Wilkinson power divider,GaAs IPD process,microstrip LC,even-mode input admittance
更新于2025-09-23 15:19:57
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Novel FDTD Scheme for Analysis of Frequency-Dependent Medium Using Fast Inverse Laplace Transform and Prony’s Method
摘要： A novel finite-difference time-domain (FDTD) approach is proposed for analysis of wave propagation in a general frequency-dependent medium. In the proposed method, formulation of the fractional derivatives in the time-domain representation is circumvented by using the fast inverse Laplace transform (FILT) and Prony’s method. The FILT is used to transform the dispersion expressed in a frequency domain into a time-domain response and Prony’s method is utilized to extract parameters and transform the time-domain responses into those in the z-domain so that they can be incorporated into the FDTD method directly. The update equation of the electric field in the FDTD method is then formulated by using the z-transformation. Stability analysis of the proposed scheme is also investigated by means of the root-locus method. Reflection coefficients of dispersive media, such as Debye, Cole–Cole, Davidson–Cole, and Havriliak–Negami media simulated in a one-dimensional domain and a three-layered biological medium of skin, fat, and muscle tissues inside a waveguide with a TE10 fundamental mode in a two-dimensional domain, are found to be in good agreement with those obtained by an analytical method over a broad frequency range, demonstrating validity of the proposed FDTD scheme.
关键词： Prony’s method,time-domain method,Cole–Cole medium,FDTD,Finite-difference,Laplace transform,frequency-dependent medium
更新于2025-09-11 14:15:04
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Nonequilibrium Environment Dynamics in a Frequency-Dependent Polarizable Embedding Model
摘要： Hybrid quantum mechanical/molecular mechanical (QM/MM) models are some of the most powerful and computationally feasible approaches to account for solvent effects or more general environmental perturbations on quantum chemical systems. In their more recent formulations (known as polarizable embedding) they can account for electrostatic and mutual polarization effects between the QM and the MM subsystems. In this paper, a polarizable embedding scheme based on induced dipoles that is both able to describe electron evolution of the embedded QM system in an efficient manner as well as to capture the frequency dependent behavior of the solvent is proposed, namely ωMMPol. The effects of this frequency dependent solvent on a time-dependent model system — the Rabi oscillations of H+2 in a resonant field — are considered. The solvent is shown to introduce only mild perturbations when the excitation frequencies of the solvent and the solute are off-resonant. However, the dynamics of the H+2 are fundamentally changed in the presence of a near-resonant excitation solvent. The effectiveness of ωMMPol to simulating realistic chemical systems is demonstrated by capturing charge transfer dynamics within a solvated system.
关键词： charge transfer dynamics,polarizable embedding,Rabi oscillations,QM/MM models,frequency-dependent polarizability,electron dynamics
更新于2025-09-10 09:29:36