Terry M. North

Investigation of the theoretical basis for using a 1 GHz TEM cell to evaluate the radiated emissions from integrated circuits

This study was initiated in order to gain a better understanding of the basis for using a 1 GHz TEM cell to evaluate the radiated emissions from integrated circuits (ICs). The authors have been involved for several years with the effort to develop procedures and standards for evaluating the EMC of ICs. One of these standards, SAE J1752/3, is being used by the IC industry to characterize high speed VLSI ICs and survey the variation of RF emissions due to changes in IC process and package parameters. This standard specifies a radiated emissions measurement system using a 1 GHz TEM cell with the IC under test on a test board that is a part of the wall above the septum of the TEM cell. In order to investigate the theoretical basis for this procedure, a model of the IC lead frame as a current loop was developed and analyzed for coupling to the septum of the TEM cell at different orientations. Test boards with current loops orientated both parallel and orthogonal to the TEM cell wall were evaluated for correlation with the model. Using a microprocessor on a test board, a comparison was made of the measured data from the 1 GHz TEM cell, the EMSCANTM circuit board analysis system and radiated field measurements using an antenna. Methods for calibration of the TEM cell were also investigated.

Characterization of the RF emissions from a family of microprocessors using a 1 GHz TEM cell

This paper examines the radiated RF emissions from a family of microprocessors expanding on our previous investigations into this area. The procedure used was SAE J1752-3, which specifies a radiated emissions measurement system using a 1 GHz TEM cell with the IC under test on a standardized test board that is a part of the wall above the septum of the TEM cell. This procedure provides a controlled test environment and has been developed to characterize high speed VLSI ICs and survey the variation of RF emissions due to changes in IC process and package parameters. Our investigation involved evaluating the effects on radiated RF emissions from the microprocessors due to processor type, operating software, die mask level, die fab site, die fab date code and fab process variation. The intent is to build a database that will facilitate an assessment of the impact of process changes on the RF emissions from microprocessors.

Measuring the radiated emissions from a family of microprocessors using a 1-GHz TEM cell

This paper presents a series of measurements of the radiated emissions from 8 and 16 bit microprocessors. The radiated emissions were measured using a 1-GHz TEM cell that incorporates the device under test (DUT) into the cell structure itself. For the 16 bit processor, samples from each of the manufacturers identified process corners were measured and compared. Two separate fabrication lines were compared for process variability. The spatial location on the wafer was measured for emissions variation. In addition, emissions were measured for a 16 bit processor as a function of the operating temperature. Finally a comparison was made between discrete implementations of a module digital core and the same circuit implemented as an multichip module (MCM).

Modeling the radiated emissions from microprocessors and other VLSI devices

This paper presents a heuristic model for describing radiated emissions from microprocessors by considering the emissions spectrum to be that of an excited, or driven, electron gas. The main idea is derived from a modification of the classical Maxwell-Boltzmann distribution of molecular velocities in an ideal gas. In this paper, that procedure is applied to the free electrons in a conducting surface, where the electrons are assumed to be in a gas state residing over the surface of the conductor. Using the conductor volume, and the excitation signal characteristics, a distribution is found that roughly corresponds to measured distributions found in microprocessors. The derived equation is applied for each event risetime, I/O switching and internal switching, and summed.

Constructing the Lagrangian of VLSI devices from near field measurements of the electric and magnetic fields

This paper describes a method whereby the Lagrangians of a set of near field measurements, over the surfaces of VLSI devices, are constructed. By studying the Lagrangian of a VLSI device, and applying least action principles, one is able to determine packaging effects over a broad frequency range and make a decision as to which package type is better in terms of its electromagnetic compatibility.

Predicting module level RF emissions from IC emissions measurements using a 1 GHz TEM or GTEM Cell - a review of related published technical papers

This paper reviews some of the many published technical papers relating to the measurement of IC emissions using a 1 GHz TEM cell or GTEM cell modified to accept an IC test board and provides a basis for correlation between these IC level measurements and module level RF emissions. We will follow the development of this methodology from the early investigations through the later applications to show the viability of the technique for IC qualification. Developments over time have shown that this method of IC emission measurement is repeatable, correlatable to other methods and provides, within limits, useful prediction of module level RF emissions performance.

Automotive EMC testing — The challenges of testing battery systems for electric and hybrid vehicles

Hybrid and electric vehicle batteries are actually an Energy Storage System whose internal module functions include: battery monitoring and control, DC to DC convertor(s), an internal battery charger and internal battery cooling control. As a result, comprehensive EMC testing requires a paradigm shift from module or component level testing to complete EMC system level testing.

Electromagnetic Compatibility of Direct Current Motors in an Automobile Environment

As the volume and complexity of electronics increases in automobiles, so does the complexity of the electromagnetic relationship between systems. The reliability and functionality of electronic systems in automobiles can be affected by noise sources such as direct current (DC) motors. A typical automobile has 25 to 100+ DC motors performing different tasks. This paper investigates the noise environment due to DC motors found in automobiles and the requirements that automobile manufacturers impose to suppress RF electromagnetic noise and conducted transients.