Using an LU Recombination Method to Improve the Performance of the Boundary Element Method at Very Low Frequencies

Many numerical electromagnetic modeling techniques that work very well at high frequencies do not work well at lower frequencies. This is directly or indirectly due to the weak coupling between the electric and magnetic fields at low frequencies. One technique for improving the performance of boundary element techniques at low frequencies is through the use of loop-tree basis functions, which decouple the contributions from the vector and scalar electric potential. However, loop-tree basis functions can be difficult to define for large, complex geometries. This paper describes a new method for improving the low-frequency performance of boundary element techniques. The proposed method does not require special basis functions and is relatively easy to implement. Numerical errors introduced by the great difference in scale between the vector and scalar electric potential are corrected automatically during the LU decomposition of the impedance matrix

Capacitive-Stemmed Capacitor

A capacitor having a stem that is designed to be inserted into a single, large-diameter via hole drilled in a printed circuit board is provided, wherein the stem may have conductive rings for making the positive and negative connections to the printed circuit board power distribution planes. Inside the capacitive stem, current, or at least a portion thereof, may be carried to the main body of the capacitor through low-inductance plates that are interleaved to maximize their own mutual inductance and, therefore, minimize the connection inductance. Alternatively, the capacitor may include a coaxial stem that forms a coaxial transmission line with the anode and cathode terminals forming the inner and outer conductors

Full-Wave Model of Frequency-Dispersive Media With Debye Dispersion Relation by Circuit-Oriented FEM

Dispersive materials play an important role in a wide variety of applications (e.g., waveguides, antenna structures, integrated circuits, bioelectromagnetic applications). In this paper, a full-wave finite-element method (FEM-SPICE) technique for modeling dispersive materials is proposed. A finite-element formulation employing Whitney elements capable of analyzing electromagnetic geometries with dispersive media is described, and a Norton equivalent network is developed for each element. The overall network can be analyzed using a circuit simulator based on SPICE, and is suitable for both frequency- and time-domain analysis. This approach exploits the flexibility of finite-element mesh generation and computational efficiency of modern circuit simulators. Simple test configurations are analyzed to validate the proposed formulation

Using the LU Recombination Method to Extend the Application of Circuit-Oriented Finite Element Methods to Arbitrarily Low Frequencies

The circuit-oriented finite-element method (FEM) is a method that combines a finite-element field solver with a circuit analyzer and is suitable for analyzing electromagnetic field/circuit coupled problems. This paper describes a significant improvement to existing circuit-oriented FEMs that reduces the number of circuit elements and eliminates low-frequency stability problems. A modified LU recombination method is used to reformulate the original field-solver matrix equations. Circuits based on the reformulated equations are relatively insensitive to numerical errors and do not contain the small-value series resistors that circuit solvers are normally forced to add in order to guarantee a stable solution. Using this approach, the circuit-oriented FEM is capable of time-and/or frequency-domain simulations of problems containing linear or nonlinear lumped elements over a wide bandwidth. Examples are provided that demonstrate the ability of the new technique to model geometries from dc to several gigahertz in a single simulation

Temperature mapping using photoacoustic and thermoacoustic tomography

Photoacoustic (PA) and thermoacoustic (TA) effects are based on the generation of acoustic waves after tissues absorb electromagnetic energy. The amplitude of the acoustic signal is related to the temperature of the absorbing target tissue. A combined photoacoustic and thermoacoustic imaging system built around a modified commercial ultrasound scanner was used to obtain an image of the target's temperature, using reconstructed photoacoustic or thermoacoustic images. To demonstrate these techniques, we used photoacoustic imaging to monitor the temperature changes of methylene blue solution buried at a depth of 1.5 cm in chicken breast tissue from 12 to 42 °C. We also used thermoacoustic imaging to monitor the temperature changes of porcine muscle embedded in 2 cm porcine fat from 14 to 28 °C. The results demonstrate that these techniques can provide noninvasive real-time temperature monitoring of embedded objects and tissue

Performance characterization of an integrated ultrasound, photoacoustic, and thermoacoustic imaging system

We developed a novel trimodality system for human breast imaging by integrating photoacoustic (PA) and thermoacoustic (TA) imaging techniques into a modified commercial ultrasound scanner. Because light was delivered with an optical assembly placed within the microwave antenna, no mechanical switching between the microwave and laser sources was needed. Laser and microwave excitation pulses were interleaved to enable PA and TA data acquisition in parallel at a rate of 10 frames per second. A tube (7 mm inner diameter) filled with oxygenated bovine blood or 30 mM methylene blue dye was successfully detected in PA images in chicken breast tissue at depths of 6.6 and 8.4 cm, respectively, for the first time. The SNRs at these depths reached ∼24 and ∼15  dB, respectively, by averaging 200 signal acquisitions. Similarly, a tube (13 mm inner diameter) filled with saline solution (0.9%) at a depth of 4.4 cm in porcine fat tissue was successfully detected in TA images. The PA axial, lateral, and elevational resolutions were 640 μm, 720 μm, and 3.5 mm, respectively, suitable for breast cancer imaging. A PA noise-equivalent sensitivity to methylene blue solution of 260 nM was achieved in chicken tissue at a depth of 3.4 cm

Estimation of the Statistical Variation of Crosstalk in Wiring Harnesses

Analyzing interference problems in vehicle wiring harnesses requires fast and accurate methods of approximating crosstalk. Worst-case approximations using lumped element models are fast and easy to use, but run the risk of overestimating problems. Statistical methods that account for the random variation of wire position help prevent overdesign, but are often difficult and time-consuming to apply and lack a clear link between problems and their cause. Here we investigate the use of simple lumped-element models to predict the statistical variation of crosstalk in wire harness bundles. Models are based on lumped-element approximations, where inductance and capacitance values are calculated for a single bundle crosssection, and only the circuit position is varied. Accuracy was evaluated by comparing results to numerical simulations. The method does a good job of quickly predicting the reasonable worst-case values of crosstalk due to inductive or capacitive coupling

Semiconductor integrated circuit chip, multilayer chip capacitor and semiconductor integrated circuit chip package

Disclosed are a semiconductor integrated circuit chip, a multilayer chip capacitor, and a semiconductor integrated circuit chip package. The semiconductor integrated circuit chip includes a semiconductor integrated circuit chip body, an input/output terminal disposed on the outside of the semiconductor integrated circuit chip body, and a decoupling capacitor disposed at a side face of the semiconductor integrated circuit chip body and electrically connected to the input/output terminal. The semiconductor integrated circuit chip cab be obtained, which can maintain an impedance of a power distribution network below a target impedance in a wide frequency range, particularly at a high frequency, by minimizing an inductance between a decoupling capacitor and a semiconductor integrated circuit chip