A novel equivalent circuit model for waveguide-separated absorption charge multiplication-avalanche photodetector (WG-SACM-APD)

Waveguide photodetectors are promising high-speed photodetectors compared to conventional photodetectors because of solving the problem of bandwidth efficiency tradeoff. The equivalent circuit model of detectors can be utilized to confirm the device performance prior to fabrication. In this paper a novel equivalent circuit model for waveguide-separated absorption charge multiplication avalanche photodetector (WG-SACM-APD) is presented. Using basic circuit components and considering the theory of linear time invariant system frequency domain modeling of this detector including parasitic sources are achieved. Finally the transfer function and detector's bandwidth with respect to the multiplication gain are also investigated and there are good agreements with experimental results.     

An equivalent circuit model for microwave-biased extrinsic photoconductors1

An equivalent circuit model for microwave-biased extrinsic photoconductors is introduced. Theoretical performance results calculated from the model are compared to experimental values of a microwave-biased mercury-doped germanium photoconductor operating at high background photon irradiance levels. The comparison indicates that the equivalent circuit model is adequate to describe the performance of microwave-biased extrinsic photoconductors. Experimental and theoretical results indicate that microwave-biased extrinsic photoconductors are high gain (G ∼10⁴) devices with a simultaneous submicrosecond speed of response.     

An equivalent circuit model for the long-wavelength quantum well infrared photodetectors

We present an equivalent circuit model for AlGaAs/GaAs long wavelength quantum well infrared photodetectors (LW-QWIPs). Bias dependence of the dark current and photoresponse is described with the aid of analogue circuit modeling technique in the TINA software. This model can be integrated with the readout circuit for the whole device circuit simulation and optimization further. The designed parameters of the LW-QWIPs can be fed into this model as user-defined circuit parameters to simulate the detector performance. The obtained results are consistent with the experimental measurements.     

SiGe HBT大信号等效电路模型

基于SiGe HBT(异质结双极晶体管)的物理模型，建立了描述SiGe HBT的大信号等效电路模型.该等效电路模型考虑了准饱和效应和自热效应等，模型分为本征和非本征两部分，物理意义清晰，拓扑结构相对简单.该模型嵌入了PSPICE软件的DEVEO(器件方程开发包)中.在PSPICE软件资源的支持下，利用该模型对SiGe HBT器件进行了交直流特性模拟分析，模拟结果与理论分析结果相一致，并且与文献报道的结果符合较好. 关键词： SiGe HBT 等效电路模型 PSPICE     

Analysis of frequency selective surface absorbers via a novel equivalent circuit method

An equivalent circuit (EC) method for absorbers design is proposed in this paper. Without using full-wave analysis, the EC method can predict the performance of the absorbers. This method is employed to synthesize broadband absorbers by inserting the resistors respectively into the single- and double-square loops structures, then two different prototypes with broadband absorbing frequency bands are manufactured and measured. By comparisons with the results both by using the full-wave analysis and by the measurements, the correctness of the new EC method is verified. Some factors which affect the absorbing bandwidth are also investigated. Due to its fast and accurate characteristics, the EC method which can be theoretically applied to arbitrary FSS is a good candidate for broadband design of the absorbers.     

The noise equivalent circuit model of quantum-dot lasers

We derive the noise equivalent circuit model of semiconductor self-assembled quantum-dot (QD) lasers (SAQDL) from the rate equations including Langevin noise sources. This equivalent circuit allows a straightforward calculation of the noise of an SAQDL combined with electronic components. Using the presented model, we study how the carrier dynamics influences relative intensity noise (RIN) of QD lasers. We demonstrate that RIN is degraded with larger inhomogeneous broadening. Furthermore, we show that RIN is enhanced for lower quantum-dot coverage level.     

An equivalent circuit model for terahertz quantum cascade lasers:Modeling and experiments

Terahertz quantum cascade lasers(THz QCLs) emitted at 4.4 THz are fabricated and characterized. An equivalent circuit model is established based on the five-level rate equations to describe their characteristics. In order to illustrate the capability of the model, the steady and dynamic performances of the fabricated THz QCLs are simulated by the model.Compared to the sophisticated numerical methods, the presented model has advantages of fast calculation and good compatibility with circuit simulation for system-level designs and optimizations. The validity of the model is verified by the experimental and numerical results.     

Threshold flux-controlled memristor model and its equivalent circuit implementation

Modeling a memristor is an effective way to explore the memristor properties due to the fact that the memristor devices are still not commercially available for common researchers. In this paper, a physical memristive device is assumed to exist whose ionic drift direction is perpendicular to the direction of the applied voltage, upon which, corresponding to the HP charge-controlled memristor model, a novel threshold flux-controlled memristor model with a window function is proposed. The fingerprints of the proposed model are analyzed. Especially, a practical equivalent circuit of the proposed model is realized, from which the corresponding experimental fingerprints are captured. The equivalent circuit of the threshold memristor model is appropriate for various memristors based breadboard experiments.     

用电路模型等效变换的方法教学RL暂态过程

教学RL回路的暂态过程时,为了改善学生对已有知识记忆的激活和建立意义明确的关联,本文使用电路模型等效变换和构建的方法,分别以初态和终态为参考状态,对RL回路的全状态响应进行了分析,直观地将此暂态过程解析为:1)从初态到终态的常系数衰减过程,2)零输入响应和零状态响应的叠加.从而实现对教学效果的提高.     

Accuracy of the equivalent circuit model using a fixed beamimpedance for klystron gain cavities

Most small-signal calculations of the modulation in a klystron's gain cavity use an equivalent circuit which includes a fixed beam impedance. Comparing this calculation to the gain calculated self-consistently, we note there are appreciable errors in both the calculated amplitude and phase of the cavity's modulation. These errors may lead to large accumulated errors in determining either the tube's small-signal or large-signal gain. Both techniques are used in a comparison with an existing S-band klystron     

利用等效电路模型计算耦合腔行波管注-波互作用

通过研究Curnow等效电路模型,得到进行单腔计算的矩阵方程,进而获得线路场方程, 结合运动方程和空间电荷场方程,从而推导出耦合腔行波管一维注波互作用非线性理论模型. 该理论能计算任意的切断、跳变、渐变等结构以及多信号模拟.利用该理论编制的软件计算了 59 GHz-64 GHz耦合腔行波管AM-PM相位失真,三阶互调以及五阶互调分量. 同时模拟得到了59 GHz-64 GHz带内饱和输出功率分布,理论结果与热测结果误差在5%以内.     

The equivalent circuit of a powder electroluminescent capacitor

An electrical equivalent circuit is proposed and analyzed for capacitors filled with powdered ZnS electroluminescent phosphor in the insulator. The basic laws of the behavior of the dielectric characteristics of the specimen in the dark and when illuminated by ultraviolet (UV) light are explained: the existence and properties of a dark frequency maximum of tg and the corresponding dispersion of capacitance C as well as the appearance of certain new maxima tg with UV illumination and their properties. The dark maximum of tg is ascribed to the conductivity of the second phase and the light ones to the photoconductivity of the nonuniform grains. The case of possible negative changes in tg and when the specimen is illuminated by UV light is also considered.A study was made in [1] of the dielectric properties of ZnS phosphor uniformly distributed in a teflon film. Measurements were carried out in weak fields when the processes associated with electroluminescence do not appear. As distinct from photophosphors, a frequency maximum of tg was found in the majority of specimens of ZnS in the dark, with a dispersion of capacitance in its region. The frequency of these photo-maxima () increased with increase in the intensity of UV illumination, and decreased with the lapse of time after cutting off the excitation. Infrared illumination shifts the light maxima to the left along the frequency axis and does not affect the dark maximum of tg at all. It is shown in [1] that this dark maximum is governed by the conductivity of the second phase, and the light maxima by the nonuniform photoconductivity in the natural grains of the phosphor. In certain specimens the conductivity of the second phase increases with temperature and in others it is unchanged. Based on [2], it was concluded that this is connected with differing content of extra-stoichiometric granules.In conclusion the author wishes to express her appreciation of F. I. Vergunas' guidance in the work.     

变张换能器的等效电路支路阻抗分析方法

本文提出了适用于弯张换能器的等效电路支路阻抗分析方法,归纳总结了一些描述IV型弯张换能器振动辐射的特性参量,通过支路阻抗分析方法计算这些特性参量可以进行换能器局部结构的优化设计.     

弯张换能器的等效电路支路阻抗分析方法

本文提出了适用于弯张换能器的等效电路支路阻抗分析方法,归纳总结了一些描述IV型弯张换能器振动辐射的特性参量,通过支路阻抗分析方法计算这些特性量可以进行换能器局部结构的优化设计。     

Analytical framework of small-gap photoconductive dipole antenna using equivalent circuit model

A compact planar antenna sources with on-chip fabrication and high directivity in order to achieve large depth-of-field for better image resolution is the prospective demand for THz imaging application. Therefore, the small-gap photoconductive dipole antennas have been explored to fulfil such applications demand. However, there are certain modalities for improving the photoconductive dipole antenna performance which need to identify to accomplish high THz average radiated power and improved total efficiency. The unit-cell small-gap photoconductive dipole antenna radiation power enhancement methods need to optimize the design parameters with photoconductive material selection from theoretical simulation. Further, the potential improvement of coupling efficiency of THz wave with air as well as femto-second laser incident efficiency is also important parameters to enhance the radiation power of small-gap photoconductive dipole antenna. In this paper, we have presented an analytical procedure employing explicit mathematical expression leading to the physical behaviour of small-gap photoconductive dipole antenna. The effects of biased lines on the antenna performance parameters are discussed with the help of proposed equivalent circuit model. We have explored the effect of gap-size on the THz radiated power and on total radiation efficiency from the proposed photoconductive dipole antennas.     

Effects of the quantum inductance on the equivalent circuit model of a resonant tunneling diode

The effects of the quantum inductance, due to the resonance lifetime of an electron in a double barrier potential, are studied in the equivalent circuit model of a resonant tunneling diode. Regions of stable and unstable circuit behavior are obtained through a small signal analysis, and phase diagrams are found using a pseudo-Monte Carlo simulation. A comparison with a previous model is made. In addition the large signal behavior of the circuit model is investigated, and a reduction in the maximum oscillator frequency is demonstrated.     

An MRI tissue equivalent lesion phantom using a novel polysaccharide material

A new polysaccharide material, TX-150, and method is described which will potentially allow formation of stable, multi-compartment MRI phantoms constructed without intervening septa. TX-150 can be made into water based gels which are nominally tissue equivalent. Although contiguous regions of different water content are not possible, as water diffusion will occur until equilibrium is reached, TX-150 gel T1 and T2 values can be adjusted independently, while maintaining a constant water composition, by appropriate additives. Unlike paramagnetic ions and chelates, metal phthalocyanines have been found to bind tightly to TX-150, thus, permitting formation of stable contiguous regions of differing T1 relaxation properties. Phantom T2 values can be effectively modified with 2-2-diphenyl-1 picrylhydrazyl, which has little affect on gel T1 values, to form septumless lesion phantoms of varying T1 and T2.     

等效回路法在离子液体电极效应中的应用

利用等效电回路模型简化离子液体的电极系统,分析了电极效应中出现的3个特征频率和各自表征的物理意义.基于离子液体介电谱实验数据,获取了等效电回路的基本参数:本体电容、本体电阻和电双层电容,进而得到离子液体样品和电双层的基本介电参数,以及与离子迁移相关的物性参数如扩散系数、迁移率、离子液体中有效离子浓度,对深入理解离子液体导电和界面机制有重要的意义.     

Modeling of a millimeter wave planar Schottky diode using both improved equivalent circuit model and 3D-EM model

In this paper, a planar Schottky varistor diode is studied and modeled by equivalent circuit method and three dimensional full wave electromagnetic (3D-EM) method, respectively. The diode's equivalent circuit is extracted from millimeter-wave small-signal S-parameter measurements. Since the package of the diode influences the electromagnetic field distribution at millimeter and sub-millimeter wavelengths, a 3D-EM model and an improved equivalent circuit model is applied to describe the field precisely. The simulated results of equivalent circuit, improved equivalent circuit and 3D-EM model are compared with the measured results. In addition, the effects caused by silver paste conductive adhesive are considered in 3D-EM model and improved equivalent circuit model. The results show that both the 3D-EM model and improved equivalent circuit model have good S-parameter consistency with measured results.     

Dynamical characteristics of an HP memristor based on an equivalent circuit model in a chaotic oscillator

To develop real world memristor application circuits,an equivalent circuit model which imitates memductance(memory conductance) of the HP memristor is presented.The equivalent circuit can be used for breadboard experiments for various application circuit designs of memristor.Based on memductance of the realistic HP memristor and Chua's circuit a new chaotic oscillator is designed.Some basic dynamical behaviors of the oscillator,including equilibrium set,Lyapunov exponent spectrum,and bifurcations with various circuit parameters are investigated theoretically and numerically.To confirm the correction of the proposed oscillator an analog circuit is designed using the proposed equivalent circuit model of an HP memristor,and the circuit simulations and the experimental results are given.