Voltage Regulator Module Noise Analysis for High-Volume Server Applications

This paper presents a methodology to analyze voltage regulator module (VRM) noise coupling problems in high-volume server applications. The technique is applied on a real engineering design. The comprehensive model includes irregular power shapes, decoupling capacitors, and dielectric and conductive loss. Irregular shaped power plane modeling is cross-checked with four separate methods to demonstrate accuracy

The genomic landscape of juvenile myelomonocytic leukemia

Juvenile myelomonocytic leukemia (JMML) is a myeloproliferative neoplasm (MPN) of childhood with a poor prognosis. Mutations in NF1, NRAS, KRAS, PTPN11 and CBL occur in 85% of patients, yet there are currently no risk stratification algorithms capable of predicting which patients will be refractory to conventional treatment and therefore be candidates for experimental therapies. In addition, there have been few other molecular pathways identified aside from the Ras/MAPK pathway to serve as the basis for such novel therapeutic strategies. We therefore sought to genomically characterize serial samples from patients at diagnosis through relapse and transformation to acute myeloid leukemia in order to expand our knowledge of the mutational spectrum in JMML. We identified recurrent mutations in genes involved in signal transduction, gene splicing, the polycomb repressive complex 2 (PRC2) and transcription. Importantly, the number of somatic alterations present at diagnosis appears to be the major determinant of outcome

Modeling of shielding composite materials and structures for microwave frequencies

Abstract—Composites containing conducting inclusions are required in many engineering applications, especially, for the design of microwave shielding enclosures to ensure electromagnetic compatibility and electromagnetic immunity. Herein, multilayer shielding structures are studied, with both absorbing and reflecting composite layers. In this paper, fiber-filled composites are considered. For modeling absorbing composites with low concentration of conducting cylindrical inclusions (below the percolation threshold), the Maxwell Garnett theory is used. For reflecting layers, when concentration of inclusions is close to or above the percolation threshold, the McLachlan formulation is used. Frequency dependencies for an effective permittivity are approximated by the Debye curves using a curve-fitting procedure, in particular, a genetic algorithm. Corresponding author: M. Y. Koledintsev

DC blocking via structure optimization and measurement correlation for SerDes channels

SerDes (Serializer/DeSerializer) is widely used in gigabit Ethernet systems, fiber-optic communication systems, and storage applications for high-speed data transmission between different ASICs (application-specific integrated circuit) with the significant advantage of saving package pin numbers. The channel connecting the Serializer/DeSerializer in two different ASICs on a PCB (Printed Circuit Board) is the SerDes channel defined in the paper. Since DC biases in different ASICs are usually different for their Serializer/DeSerializer circuits, DC blocking capacitors are then necessary to block the DC path for signal transmission through the SerDes channel. It is known that the trace impedance on a PCB can be well controlled in manufacturing while it is difficult for a DC blocking via structure. Therefore, the blocking via structure is the main discontinuity contributor of the SerDes channel. In this paper, two different DC blocking via structures are studied. The performances of the two structures are compared and correlated up to 20 GHz with full-wave modelling and measurements. This study reveals the advantages/disadvantages of the two via blocking structures. A via optimization tool, which is based on the cavity resonance algorithm to speed up the optimization, is used to obtain the optimized parameters for the two blocking via structures, and the following full-wave simulations give further performance explorations of the two via structures

Feature selective validation (FSV) for validation of computational electromagnetics (CEM). Part II -assessment of FSV performance

The feature selective validation (FSV) method has been proposed as a technique to allow the objective, quantified, comparison of data for inter alia validation of computational electromagnetics. In the companion paper "Feature selective validation for validation of computational electromagnetics. Part I-The FSV method," the method was outlined in some detail. This paper addresses two specific issues related to the implementation of the FSV method, namely "how well does it produce results that agree with visual assessment?" and "what benefit can it provide in a practical validation environment?" The first of these questions is addressed by comparing the FSV output to the results of an extensive survey of EMC engineers from several countries. The second is approached via a case study analysis