Thermal analysis of layered electronic circuits with Green's functions

This paper is focused on the Internet Graphical Simulation Tool for computer analysis of electronic circuits and describes all main features and advantages of using this tool for computer modeling and simulations of electronic circuits. Internet Graphical Simulation Tool (IGST) provides easy way for modeling and simulation of electronic circuits without necessity of purchasing expensive software license or installing some special simulation software tools. IGST can be used anywhere access to the Internet is available. IGST is composed from three main parts which provide basic PSpice analyzing functionality for any electronic circuit. The first part of the IGST is a GUI for interactive drawing and editing of electronic circuit’s schema. The second part is a simulation core from freely available older version of the PSpice simulation software and the last part of the IGST is an Internet graphical environment for displaying simulation results. Based on these three parts the IGST creates complex tool for easy analysis of electronic circuits through the Internet.

Thermoelasticity of multilayered plates with imperfect interfaces

With the development of China’s urbanization construction, the proportion of urban power distribution cables is increasing. The existing models for the temperature calculation of urban medium and low voltage three-core cables regard the filler layer and inner sheath as isothermal body structure for research and analysis, and do not take into account the temperature inhomogeneity characteristics of the three-core cable structure itself. In the paper, the uneven distribution characteristics of the buffer layer of the three-core cable are considered, and then the temperature distribution of the inner sheath is analyzed, and the distributed modeling of the inner sheath is carried out by drawing on the idea of analogous distributed model of the electric circuit, and from the heat flow theory, the heat flux assigned to each segment of the structure such as each inner sheath is derived, and the steady-state thermal circuit model of the three-core cable is established based on the principle of equivalency, and the finite element computation method is adopted to recognize the thermal circuit parameters, and finally, after the simulation results are compared with the simulation results, the temperature of the three-core cable structure itself is considered as an isothermal structure. Finally, after comparing with the simulation results, the accuracy of the thermal circuit model reaches 95%, the change of ambient temperature has less influence on the thermal circuit model, and the model has high robustness, which provides support for the on-line detection technology of the state of three-core cables.

A hierarchical symbolic analyzer (SAGA2) for the analysis of electronic circuits is presented. SAGA2 analyzes lumped, linear, or linearized (small-signal) circuits in the S- and Z-domain. For large circuits, a hierarchical two-port method is used that is two to three order faster than that without using the hierarchical method. Also, the memory used is dramatically reduced.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A comprehensive analysis of heat distribution and thermal mixing in steady laminar natural convective flow in discretely heated square cavities has been carried out via Bejan’s heatlines. Heatlines are analogous to streamlines and heat energy flow may be visualized by heatlines similar to streamlines which display fluid flow. The trajectories of heatlines indicate direction and magnitude of heat flow and zones of high heat transfer. The heatline approach is implemented to study heat flow in the following three different square cavities which are filled with water (Pr = 7): (1) uniformly heated bottom wall (2) distributed heating with heat sources present on central portions of the walls and (3) multiple heat sources on the walls of the cavity. Top wall is maintained adiabatic in all the cases. Galerkin finite element method with penalty parameter has been used to solve non-linear coupled partial differential equations for flow and temperature fields over a range of Rayleigh numbers (Ra = 103–105). The Galerkin method is further employed to solve the Poisson equation for streamfunctions and heatfunctions. Finite discontinuity exists at the junction of hot and cold walls leading to mathematical singularity. Solution of heatfunction for such type of situation demands implementation of non-homogeneous Dirichlet conditions. Heatlines illustrate that in uniformly heated bottom wall case, the heat from the bottom wall is not adequately distributed to the lower portion of side walls which leads to low temperature in those regions (case 1). In order to improve the heat distribution, the uniform heat sources is divided into three parts and are applied along the central regimes of the walls (case 2). It is observed that, heat distribution and thermal mixing in the cavity is significantly enhanced. However, the lower corner portions are still retained cold. In case 3, multiple heat sources are placed along the walls of the cavity along with heat sources at lower corner regions of the cavity. Heatlines indicate that, the temperature at the core is reduced compared to case 2, but uniform heat distribution results in uniformity of temperature across large area of cavity.

Transient analysis of Switching Power Converter (SPC) circuits is a computationally expensive task. This high expense arises from the fact that these circuits are driven by a clock with a period that is very small compared to the time interval the designer is typically interested in. Envelope-Following (EF) technique has been recently proposed in the literature for efficient time-domain simulation of SPC circuits. In this paper, a parallel high-order EF method, which is based on Obreshkov-Formula, is presented for analysis of SPC circuits. A numerical example is presented to demonstrate the efficiency and scalability of the proposed method on parallel platforms.

We describe a systematic method for obtaining the coupling coefficients due to diffraction orders less than the grating order of second- and higher order resonant complex gratings in a multilayer structure. This method is based on an improved Green's function, and its distinguishing feature is its use of the transfer matrix method to simplify the theoretical analysis for obtaining the Green's function in multilayer structures. More importantly, it is also shown that by introducing gain or loss in second- and higher order resonant gratings, the range of controlling the total coupling coefficient becomes wider than those in first-order complex gratings or second order index gratings. Concepts like in-phase and anti-phase gratings are generalized in this type of grating. Finally, guidelines for designing complex-coupled DFB lasers with second- and third-order grating are also presented.

Computationally efficient large-change statistical analysis of linear electronic circuits

An efficient method-of-moments (MoM) solution is presented for analysis of multilayer microstrip antennas and circuits. The required multilayer Green's functions are evaluated by the discrete complex image method (DCIM), with the guided-mode contribution extracted recursively using a multilevel contour integral in the complex /sub /spl rho//-plane. An interpolation scheme is employed to further reduce the computer time for calculating the Green's functions in the three-dimensional (3-D) space. Higher order interpolatory basis functions defined on curvilinear triangular patches are used to provide necessary flexibility and accuracy for the discretization of arbitrary shapes and to offer a better convergence than lower order basis functions. The combination of the improved DCIM and the higher order basis functions results in an efficient and accurate MoM analysis for 3-D multilayer microstrip structures.

In this paper, a new multilevel Green's function interpolation method (MLGFIM) is presented to solve integral equations for large-scale electrostatic problems. In MLGFIM, the problem domain is first divided into multilevel cubes. Next, the peer-level Green's function interpolation technique is employed, and then, a new lower-to-upper-level Green's function interpolation technique is devised. They are used with the multilevel discretization to speed up the matrix-vector multiplications in the iterative solution in which a computational complexity of O(N) is achieved. The MLGFIM is used to extract the capacitances encountered in radio frequency integrated circuits (RFICs) and microelectromechanical systems. Moreover, to demonstrate its efficiency both in simulation speed and memory storage requirement, MLGFIM is compared with FastCap for free space problems and applied to extract capacitances from multilayered structures. For problems with 375,000 unknowns, the proposed method only requires 343 MB of computer memory.

This paper presents an efficient technique to evaluate the Green's functions of single-layer and multilayer structures. Using the generalized pencil of function method, a Green's function in the spectral domain is accurately approximated by a short series of exponentials, which represent images in spatial domain. New compact closed-form spatial-domain Green's functions are found from these images using several semi-infinite integrals of Bessel functions. With the numerical integration of the Sommerfeld integrals avoided, this method has the advantages of speed and simplicity over numerical techniques, and it leads to closed-form expressions for the method-of-moments matrix coefficients. Numerical examples are given and compared with those from numerical integration.

A superlens is a slab of metal sandwiched between two dielectric layers. This structure can produce the image of an object in close vicinity without suffering from diffraction limit. Better resolution can be achieved by using a multilayer structure of metal and dielectric. In this paper, a new numerically accurate and efficient method is proposed to analyze a multilayer superlens structure. A Method of Moment (MoM) solution of the Magnetic Field Integral Equation (MFIE) formulation of the problem using Complex Images (CI) representation of the required Green's function is employed. First a single slab of silver as a superlens at 356nm and 633nm wavelengths will be analyzed, next a multilayer structure will be designed to overcome the diffraction limit of the single layer structure in the visible light frequency range.

Analysis and design of analogue electronic circuits using DPI methods — Part 2: circuits containing different types of active devices Circuits with combinations of bipolar and field effect transistors as active devices are studied. It is shown that dealing with such problems poses no additional difficulties. An example is given.

A new finite element technique that allows nonlinear time domain analysis of power electronic circuits containing magnetic components is presented. The new technique is shown to compute the same voltage waveform in a nonlinear RLC circuit as previously published circuit techniques. The new technique is demonstrated for a circuit containing an inductor with a nonlinear B-H curve, finite conductivity and a given geometry including air gaps. >

A new simulation technique for analysis of power electronics circuits is presented. It is based on using the Chebyshev polynomial to derive an adaptive stepwise quadratic state-space model for each piecewise-linear circuit topology, where the state-space equation sets are integrated with modified nodal formulations (MNF). The key feature of this algorithm is to determine an optimum step size for the model to achieve desired accuracy. The switching instants are directly calculated by solving simple quadratic equations. No prior knowledge of the circuit operations is required. The theoretical predictions are verified with the results obtained in the available literature.