Electromagnetics
As Published

The “Current Driven Model”
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Experimental Verification & the Contribution of Idd Delta to Digital Device Radiation
Several researchers have proposed that a primary source of emissions from digital devices is due to the partial inductance of the return trace on printed circuit boards. In this “current driven model,” RF currents derived from the nanosecond rise time of periodic signals such as clocks create a voltage across the return due to this inductance. This paper reports on an experimental verification of this model, but points out apparent limitations  at frequencies above a certain point, internal characteristics of integrated circuits such as Idd Delta appear to be the dominate cause of emissions, at least in the circuits examined.

A Simplified Algorithm for the Selection of Materials used to Construct Open Area Test Sites
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One of the most critical decisions to be made in the construction of an Open Area Test Site (OATS) is the selection of materials to be used for weather protection. For common construction materials, it is the dielectric constant and the thickness which best predicts their suitability. This paper presents a simple algorithm for selecting materials based on their dielectric constants and thicknesses.

Circuit Models Make Shield Design Simple
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Inadvertent magnetic and electric field coupling limits the dynamic range of amplifiers, lowers noise margins and creates unwanted noise. While every engineer knows that shielding can prevent coupling, for many shielding is a vaguely understood concept. Part of the reason is the way that shielding concepts are traditionally taught – physicist’s concept of fields and flux is usually used. It is possible however to explain shielding theory using more familiar circuit concepts.

EMI: Why Devices Radiate
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Many of the problems associated with emissions from electronic equipment can be explained using the concept of “lost flux.” Any circuit will produce magnetic flux. However some of this flux does not remain confined to the circuit but instead envelopes it. This lost flux creates a common mode voltage across the circuit causing attached conductors to radiate. In this article we explore the concept of lost flux and through a series of experiments, demonstrate how it is possible to design circuits to minimize unwanted radiation.
 Know the Theory Of Partial Inductance to Control Emissions
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The theory of partial inductance is a powerful tool for understanding why digital circuits radiate. In this article we explore the theory of partial inductance, and then apply it printed circuit board geometries. Using the theory, we can predict emissions from circuits and design strategies to mitigate them.
 Minimizing Ringing and Crosstalk
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In this article, we explore strategies to minimize ringing and crosstalk in both microstrip and stripline designs.
 Rethinking the Role of Power and Return Planes
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Good noise control calls for using power and return planes in a configuration that provides for low RF impedance. In this article, we explore the feasibility of using ground and return planes not only to provide low impedance, but to provide shielding as well. Using ground and return planes as a shield prevents flux from escaping and enveloping the entire circuit board. “Lost flux” is a primary cause of emissions from electronic circuits.
 A Dash of Maxwell's: A Maxwell's Equations Primer, Chapter 1: Introduction
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Maxwell’s Equations are eloquently simple yet excruciatingly complex. These equations are literally the answer to everything RF but they can be baffling to work with. In this six part series, we will explain Maxwell’s Equations one step at a time, beginning with its application to the “static” case, where charges are fixed, and only direct current flows in conductors.
 A Dash of Maxwell's: A Maxwell's Equations Primer, Chapter 2: Why Things Radiate
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In this chapter, we apply Maxwell’s Equations to the “dynamic” case, where magnetic and electric fields are changing. In doing so we introduce Maxwell’s Equations in their “integral form.”
 A Dash of Maxwell's: A Maxwell's Equations Primer, Chapter 3: The Difference a Del Makes
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Simple in concept, the integral form of Maxwell’s Equations (Chapter 2) can be devilishly difficult to work with. To overcome that, scientists and engineers have evolved a number of different ways to look at the problem including the “differential form” of the equations. These use the del operator. They look more complex, but they are actually simpler.
 A Dash of Maxwell's: A Maxwell's Equations Primer, Chapter 4: Equations Even A Computer Can Love
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In this installment, we will describe Maxwell’s Equations in their “computational form,” a form that allows our computers to do the work.
 A Dash of Maxwell's: A Maxwell's Equations Primer, Chapter 5: Radiation From A Small Wire Element
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By using Maxwell’s Equations in their “computational” form, we can solve for fields emanating from any given assemblage of sources and conductors simply by knowing the distribution of the currents and charges. In this installment, we put these equations to work by computing the radiation from a simple structure, a short wire element.
 A Dash of Maxwell's: A Maxwell's Equations Primer, Chapter 6: The Method of Moments
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We end our series on Maxwell’s Equations with a derivation of the Method of Moments. We will then make the transition from theory to practice by first attempting to compute the characteristics of a dipole by hand, and then by demonstrating that a computer can do the same thing in just a few seconds.