The Influence of Test Parameters on TEM Cell Measurements of ICs

The IEC 61967-2 TEM cell standard allows for variations in test parameters which may cause variations in the measured emissions from integrated circuits (ICs). To test the impact of these parameters, two printed circuit boards were designed within the IEC standard using poor PCB design strategies and using good design strategies. Emissions from three pin-for-pin compatible 8051 microcontrollers were tested. Emissions were measured using both PCBs, changing the PCB configuration, and changing test parameters like the program running on the IC, the rise time of the input clock, and I/O switching. Emissions from the poor PCB were about 3-8 dB higher than emissions from the good PCB. A change in the program run by the IC, the clock rise-time, and I/O caused a 4-15 dB change in emissions. Emissions differed considerably among the ICs. Possible causes for variations in emissions with the test parameters are discussed

Hardware-Software Co-Verification in an Undergraduate Laboratory

Skills in hardware-software co-design are quickly becoming critical to product development in high-technology computer industries. Systems-on-silicon typically include a considerable amount of software as well as custom hardware and are increasingly difficult to develop using traditional techniques. To satisfy a growing demand in industry, students in electrical Engineering; computer Engineering; and computer science should be introduced to concepts of hardware-software co-design at the undergraduate level. This paper examines a new laboratory at the University of Missouri-Rolla in which students in Electrical and Computer Engineering are exposed to modern system design concepts through the use of hardware-software co-simulation. Key tools used in the course including a hardware prototype consisting of an 8051 microcontroller and a field programmable gate array, and a VHDL model of the prototype are discusse

Generation of Synthetic-Focus Images from Pulse-Echo Ultrasound using Difference Equations

To produce a complete-dataset, pulse-echo image requires a knowledge of the time of flight (TOF) from each source to each sensor in the transducer array for each site to be imaged. Increasing the speed of TOF calculation is important in adaptive-focus schemes. The authors determined TOF more rapidly than via direct calculation by representing TOF surfaces by two-dimensional (2-D), positive-integer-degree polynomials implemented in their forward-difference form. Errors which accumulate due to the use of a difference equation depend on the degree of the polynomial and on the size of the image. The number of bits needed to address echo samples in backscatter memory and the allowable error define the minimum precision needed for accurate values of TOF, Accurate calculation of TOF, expressed as 10-b addresses in backscatter memory, for each pixel in a 512 x 512 image with a second-degree difference equation requires 44 b of precision, Using the complete dataset from a 32-element array and a second-degree approximation to TOF on a typical graphics workstation reduced generation time of a 512 x 512 image from 702 to 239 s. Parallel formulation of both the TOF calculation and the retrieval and summation of echo samples resulted in significant further reduction in image-generation time. Parallel implementation on a SIMD array with 4096 processors, each of which had an indirect-addressing mode, allowed the generation of a 512 x 512 image in 16.3 s

Estimation of Heart-Surface Potentials using Regularized Multipole Sources

Direct inference of heart-surface potentials from body-surface potentials has been the goal of most recent work on electrocardiographic inverse solutions. We developed and tested indirect methods for inferring heart-surface potentials based on estimation of regularized multipole sources. Regularization was done using Tikhonov, constrained-least-squares, and multipole-truncation techniques. These multipole-equivalent methods (MEMs) were compared to the conventional mixed boundary-value method (BVM) in a realistic torso model with up to 20% noise added to body-surface potentials and ±1 cm error in heart position and size. Optimal regularization was used for all inverse solutions. The relative error of inferred heart-surface potentials of the MEM was significantly less (p \u3c 0.05) than that of the BVM using zeroth-order Tikhonov regularization in 10 of the 12 cases tested. These improvements occurred with a fourth-degree (24 coefficients) or smaller multipole moment. From these multipole coefficients, heart-surface potentials can be found at an unlimited number of heart-surface locations. Our indirect methods for estimating heart-surface potentials based on multipole inference appear to offer significant improvement over the conventional direct approach

Predicting TEM Cell Measurements from Near Field Scan Data

A procedure is proposed for predicting TEM cell measurements from near field scans by modeling near-field scan data using equivalent sources. The first step in this procedure is to measure the tangential electric and magnetic fields over the circuit. Electric and magnetic fields are estimated from probe measurements by compensating for the characteristics of the probe. An equivalent magnetic and electric current model representing emissions is then generated from the compensated fields. These equivalent sources are used as an impressed source in an analytical formula or full wave simulation to predict measurements within the TEM cell. Experimental verification of the procedure using a microstrip trace and clock buffer show that values measured in the TEM cell and calculated from near field scan data agree within a few decibels from 1 MHz to 1 GHz

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

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

A Software Debugger Interface for an 8051 Hardware Model

A VHDL model of the 8051 microcontroller is a key component for a course in hardware-software codesign, in its second year of development at University of Missouri-Rolla. Our paper discusses a software-centric user interface developed for this model using Tcl/Tk. preliminary experience with using the debugger in an undergraduate laboratory is discussed

Electromagnetic Emissions Stimulation and Detection System

A system and method for detecting and identifying electronic devices based on their unintended electromagnetic emissions (“UEE”) signals is presented. During device classification, UEE signals are measured from a plurality of test devices and characteristic data is obtained from the UEE signal emitted from each test device. Using the characteristic data, a threshold value and ideal pulse template can be determined for each test device and stored in a memory. An ideal stimulation signal is also determined for each test device and stored in the memory. During device detection, the ideal stimulation signal is applied to the environment in which a target device is suspected of being located. Stimulated UEE signals are measured from the target device and processed. The processed measurement data is compared to stored power threshold values and ideal pulse templates to determine if the target device is present

Design and Construction of an Arbitrary Pulse Compressive Amplifier

Compressive Pulse Amplifiers Are a Class of Amplifiers that Convert Long Low Amplitude Signals into Very Broadband Pulses of High Amplitude, Yielding a Very High Instantaneous Peak Power Output Pulse. However, in the Realm of Electronic Immunity and Susceptibility Testing, Very Broadband Short Pulses Are Not Always Desired. This Work Presents a Design for a Compressive Amplifier that is Aimed at Creating Arbitrary Pulsed Signals of Varying Bandwidths. Limitations of the Achievable Gain and Methods Used Are Discussed