Characterizing the Electric Field Coupling from IC Heatsink Structures to External Cables Using TEM Cell Measurements

One method for evaluating the unintentional radiated emissions from integrated circuits (ICs) involves mounting the IC on a printed circuit board (PCB) embedded in the wall of a transverse electromagnetic (TEM) cell. The signal voltages on the IC and its package produce electric fields that can couple to cables and other structures attached to the PCB, inducing common-mode currents that can be a primary source of unintentional radiated emissions. The signal currents in the IC and its package produce magnetic fields that can also result in common-mode currents on larger radiating structures. This paper describes a TEM cell measurement method employing a hybrid to separate the electric field coupling and the magnetic field coupling. The results of this measurement can be used to determine the product of the IC\u27s self-capacitance and the effective voltage that drives this capacitance. This voltage-capacitance product characterizes the IC\u27s ability to drive common-mode currents onto cables or enclosures due to electric field coupling. This information can then be used to estimate the resulting radiated emissions

Estimating Maximum Radiated Emissions from Printed Circuit Boards with an Attached Cable

The common-mode current induced on cables attached to printed circuit boards can be a significant source of radiated emissions. Previous studies have shown that coupling from electric and magnetic field sources on circuit boards can be effectively modeled by placing equivalent voltage sources between the board and the cable. The amplitude of these equivalent sources can be estimated by using closed-form equations; however, estimates of the radiated emissions from these board-cable geometries have required full-wave simulations, and full-wave simulation results depend on the exact cable length and placement, which are not normally fixed during radiated emissions testing. This paper develops a closed-form equation to estimate the maximum radiated fields from a voltage source driving a board relative to an attached cable over a ground plane. This equation is evaluated for various cable and board geometries by comparing the calculated results to full-wave simulations. The maximum radiation calculated by using the closed-form expression generally predicts the peak full-wave simulation results within a few decibels for various board sizes and cable lengths

An Experimental Investigation of Higher Order Mode Suppression in TEM Cells

Transverse electromagnetic (TEM) cells can be used to evaluate the electric and magnetic fields coupling from integrated circuits (ICs). The propagation and reflection of higher order modes in the cells limits the bandwidth of TEM cells. This paper investigates several methods for suppressing higher order modes in TEM cells in order to extend the applicable frequency range without changing the test topology. Numerical models and measurements of a modified TEM cell demonstrate how higher order mode suppression techniques can extend the useful frequency range of a TEM cell for IC measurements from 1 to 2.5 GHz

Analysis of Chip-Level EMI using Near-Field Magnetic Scanning

Integrated circuits (ICs) are often a significant source of radiated energy from electronic systems. Well designed ICs maintain good control of the currents that they generate. However, poorly designed ICs can drive high-frequency noise currents onto nominally low-frequency input and output pins. These currents can excite unintentional radiating structures on the printed circuit board, resulting in radiated emissions that are difficult or expensive to control. The paper discusses the use of magnetic near-field scanning techniques to measure the current distribution in IC packages. This technique is applied to common ICs, including a clock driver, a memory module and a field programmable gate array (FPGA). Results show that near-field magnetic scanning is an effective tool for investigating chip-level EMI problems

Radiation Mechanisms for Semiconductor Devices and Packages

VLSI semiconductor devices are often the source of radiated electromagnetic emissions from electronic devices. Noise coupled from these devices to resonant structures on the printed circuit board, resonant cables or resonant enclosures can result in EMI problems that are difficult or expensive to solve at the board or system level. This paper reviews three mechanisms by which noise can be coupled from semiconductor devices and packages resulting in radiated electromagnetic emissions

Association of Heart Rate Variability in Taxi Drivers with Marked Changes in Particulate Air Pollution in Beijing in 2008

BACKGROUND: Heart rate variability (HRV), a marker of cardiac autonomic function, has been associated with particulate matter (PM) air pollution, especially in older patients and those with cardiovascular diseases. However, the effect of PM exposure on cardiac autonomic function in young, healthy adults has received less attention. OBJECTIVES: We evaluated the relationship between exposure to traffic-related PM with an aerodynamic diameters <= 2.5 mu m (PM(2.5)) and HRV in a highly exposed panel of taxi drivers. METHODS: Continuous measurements of personal exposure to PM(2.5) and ambulatory electrocardiogram monitoring were conducted on I I young healthy taxi drivers for a 12-hr work shift during their work time (0900-2100 hr) before, during, and after the Beijing 2008 Olympic Games. Mixed-effects regression models were used to estimate associations between PM(2.5) exposure and percent changes in 5-min HRV indices after combining data from the three time periods and controlling for potentially confounding variables. RESULTS: Personal exposures of taxi drivers to PM(2.5) changed markedly across the three time periods. The standard deviation of normal-to-normal (SDNN) intervals decreased by 2.2% [95% confidence interval (0), -3.8% to -0.6%] with an interquartile range (IQR; 69.5 mu g/m(3)) increase in the 30-min PM(2.5) moving average, whereas the low-frequency and high-frequency powers decreased by 4.2% (95% CI, -9.0% to 0.8%) and 6.2% (95% CI, -10.7% to -1.5%), respectively, in association with an IQR increase in the 2-hr PM(2.5) moving average. CONCLUSIONS: Marked changes in traffic-related PM(2.5) exposure were associated with altered cardiac autonomic function in young healthy adults.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000273292800029&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Environmental SciencesPublic, Environmental & Occupational HealthToxicologySCI(E)PubMed65ARTICLE187-9111

Determination of High Frequency Package Currents from Near-Field Scan Data

Integrated circuits (ICs) are often a significant source of radiated energy from electronic systems. Near-field magnetic scanning is an effective tool for measuring the current distribution in IC packages and investigating chiplevel EMI problems. This paper discusses analysis of near-magnetic field scan data using tangential and normal field measurements. Results show that combining near-field scan results from probes with multiple orientations is an effective way to identify the current paths in IC packages

Application of Transmission Line Models to Backpanel Plated Through-Hole Via Design

This paper introduces an approach of using a plated through-hole (PTH) via transmission-line model in the design of a thick printed circuit board, such as a backpanel. Full wave FEM modeling of a section of backpanel containing a differential via pair was compared with a transmission model. Computed values of the differential transmission loss agreed within an acceptable range for engineering studies, yet the transmission line model results required less than 2% of the computation time that the full wave model required. Effects of via spacing, via diameter and trace thickness were also examined