ELECTROMAGNETIC TOPOLOGY: ANALYSIS OF RF EFFECTS ON ELECTRICAL SYSTEMS

ELECTROMAGNETIC TOPOLOGY: ANALYSIS OF RF EFFECTSON ELECTRICAL SYSTEMS

F. M. Tesche

Prepared UnderAFOSR MURI Grant with

University of Illinois at Chicagoand

Clemson UniversityUniversity of Houston

University of Illinois at Urbana-ChampaignUniversity of Michigan

June 13, 2001

ELECTROMAGNETIC TOPOLOGY – Slide 2/32

Outline of Presentation

Overview

Introduction to EM Topology

Applications of Topology for the MURI Project

Summary


Statement of the Project To evaluate the response of electrical systems to radiated

EM field environments– Focus is on upset or damage of digital systems

– For fast transient or pulsed CW excitations at GHz frequencies

Source IncidentEM Fields

IlluminatedSystem

Internal Circuitry

Sourcegenerator

Parabolicdish reflector

Conical transmissionline feed structure

Matchingimpedances

Hex

Eex

Power line

Communicationline

SCAMP

(GFE)

ExternalPwr

Supply

Control SensorLogic Card

FiberMux

AC/DCConverter

TempControls

Pallet PowerDistribution Box

Conduit

CommercialPower

AirConditioner

HeaterPower Line

Utility Outlet

Conduit(Open To Radome)

Radome Enclosure

Pallet

UPS

FiberMux

Control StatusLogic Card

AC/DCConverter

HEMP Enclosure

GFE Computer

GFE Printer

KIV-7 GFE

GrowthCapability

HEMP Enclosure

ROC Standard 19" Rack(Unshielded)

AUX Port

KEY

HEMP Shielding

HEMP FiltersMOVs

AUX Port

ROC Power Distribution

Conduit

Conduit

Power Cable

Power Cable

Power Cable

Power Cable

Power Cable

HEMPHardened

HEMPHardened

HEMP Hardened

Primary PowerHEMP Filters

Circuit A1

Digital ComponentsRequirement is to determine behavior of the digital

circuitry to the EM excitation


Problem Statement (con’t.)

Pertinent issues to be addressed in the MURI project:– To develop EM interaction models for high frequency/fast

transient environments,– To obtain fundamental insight into the interaction of these

EM environments with digital circuitry, Considering both components and subsystems For both upset and damage

– To develop methods for testing digital systems,– To develop mitigation techniques for digital systems,– To document and distribute MURI results,

Through development of specifications and standards Liaisons with government and industry partners

– To develop and maintain and basic EM capability for DOD and industry.



Overview



Summary


How to Represent an Electrically Complex System ?

The analysis of electrically large systems is difficult. This is due to the complexity of the system and the different ways that

EM energy can interact with the system:– Inductive, capacitive and galvanic coupling to conductors,– Direct EM radiation coupling,– Current and charge propagation on conductors,– EM field penetration through apertures,– Diffusive penetrations through imperfect conductors, and– Cavity-mode resonances.

Early attempts at developing analysis models for such systems were hampered by not having a structured way of decomposing the system into smaller parts. – This led to models with errors frequently exceeding 30 dB. (See

Carter, J. M., and W. L. Curtis, “Common Mode Model Development for Complex Cable Systems”, Boeing Company, AFWL-TR-74-60, 1974.)


Modeling Can Be Based on EM Topology The system can be thought of as consisting of several layers of

conducting surfaces which shield the interior.– Known as the “onion” concept of shielding (as described by

Ricketts, et. al., EMP Radiation and Protective Techniques, John Wiley & Sons, New York, 1976.)

This idea was initially developed by C. E Baum and later formalized in the literature:– Baum, C. E., “How to Think About EMP Interaction”, Proceedings

of the 1974 Spring FULMEN Meeting, Kirtland AFB, April 1974.– Tesche, F. M., et. al., “Internal Interaction Analysis: Topological

Concepts and Needed Model Improvements”, Interaction Note Series, IN-248, October 1975.

– Tesche, F. M., "Topological Concepts for Internal EMP Interaction," IEEE Trans. AP, Vol. AP-26, No. 1, January 1978.

– Baum, C. E., "Electromagnetic Topology for the Analysis and Design of Complex Electromagnetic Systems", Fast Electrical and Optical Measurements, Vol. I, eds. I.E. Thompson and L.H. Luessem, Martinus Nijhoff, Dordrecht, 1986.


Models in Electromagnetics

In EM applications, models are based on Maxwell's equations– and the EM topology of the system

From these equations, many different solution approaches are possible:

Topology is a key element to the model

development

AnalyticalSolutions

DiscreteMethods

Maxwell'sEquations

ElectricalModel

PhysicalConfiguration

IntegralEquations

TransmissionLine Methods

“Back ofEnvelope”

HybridMethods

GeometricalOptics, etc.

SystemTopology


Analysis Using EM Topological Concepts is Conceptually Simple

The system is examined for the principal shields or EM “barriers”

Imperfections in these shields are noted and categorized A signal flow diagram is constructed Models are developed for important aspects of the signal

path An analysis is performed


The First Step in Model Development is to Determine the Topological Diagram

This is a description of the principal shielding surfaces in the system and their interrelations

Real shields are not perfect, and the external EM energy can enter by one or more of the following mechanisms:– hard-wired penetrations, formed by wires, cables or other

conductors

– aperture penetrations through holes in the shield, and

– diffusion through the barrier material


Example of the Topological Approach

Simplified illustration of a hypothetical facility excited by an external EM field.

Shielded Facility

Gasket

Air vent

Seams

Conduit

Hex

Eex

Excitation EM Field

Accesspanel

Door

Power line

Weatherhead

Communicationline


Topological Representation of the Facility

An EM interaction model is developed using the system topological and interaction diagrams:

ExternalBarrier

(Facility)

External EM Environent

Power LinePenetration

Signal LinePenetration

InternalBarrier

(Equipment)

Internal EMEnvironment

DiffusivePenetrations

AperturePenetrations

Internal FieldCouplingSystem Response

EM Barrier (Shield)Conductor TransmissionField TransmissionBarrier PenetrationEM Field PointField ExcitationResponse Location

Key

The topological diagram shows the shielding surfaces of the system and their interrelations

The interaction diagram shows the paths that EM energy can take in the system to provide a response at equipment

Penetrations of the EM energy occur at imperfections in the shielding surfaces

Propagation occurs as energy moves from one location to another in the system


The Interaction Sequence Diagram Describes the Entire Interaction Process

Illustrated here is a more complete representation of an interaction diagram for a complex facility

Current InjectionCoupling to Conductors

ConductorPenetration

AperturePenetration

DiffusivePenetration

Pulse PowerProduction

WaveformShaping

InternalEquipmentExcitation

EquipmentResponses

DamageThresholds

EquipmentFailure

NoEffect

EquipmentUpset

EM FieldRadiation from

Antenna

EM Interactionwith System

Exterior

EM FieldCoupling to

Internal Conductors

InternalConductor

Propagation

SOURCE

COUPLING

PENETRATION

INTERNALCOUPLING

RESPONSES


A Transmission Line Approximation to the EM Interaction Process The most important EM interaction paths are usually the

conductive paths (transmission lines consisting of cables and wires)

ExternalBarrier

(Facility)




InternalBarrier

(Equipment)





EM Barrier (Shield)Conductor TransmissionField Transmission

Key

ExternalBarrier

(Facility)




InternalBarrier

(Equipment)





EM Barrier (Shield)Conductor Transmission

Key

– A common low frequency approximation is to neglect the EM field couplings and treat only the conductors


The BLT Equation – A Solution for the Transmission Line Network The BLT equation† describes the voltage or current

responses on a network of transmission lines

† Baum, C.E., Liu, T.K, & Tesche, F.M.,”On the Analysis of General Multiconductor Transmission Line Networks”, Interaction Note 350, Kirtland AFB, NM, 1978

The network consists of interconnected single-wire or multiconductor transmission lines

Impedance elements represent the equipment loads

Forward and backward traveling waves exist on each transmission line “tube” in the network

I - I +Incident and scattered waves exist at each junction (or node) in the network

I inc

I sca


The BLT Equation – A Solution for the Transmission Line Network (con’t.) The current at all nodes in the network is described by the

BLT equation– This is a matrix equation involving matrices as elements – a

supermatrix equation

E:::1

SSUYI cL

Supermatrix multiplication

Identity supermatrix

Response supervector containing all wire currents at each node in the network

Voltage scattering supermatrix for all nodes

Propagation supermatrix for all tubes (suitably re-ordered)

Source supervector containing the excitations of each transmission line tube


The BLT Equation – A Solution for the Transmission Line Network (con’t.)

A similar BLT equation can be developed for the voltages at each wire at the nodes of the network

E::1

SSUVL


Numerical Realizations of the BLT Equation

The initial BLT analysis code, QV7TA, was developed by Tesche and Liu in 1978 † – Has been used for aircraft, missile and satellite analysis for

DOD programs

† Tesche, F. M., and T.K. Liu, “User Manual and Code Description for QV7TA: a General Multiconductor Transmission Line Analysis Code”, LuTech, Inc. report, August 1978.

† † CRIPTE Code Users Guide, ESI/ONERA, France, 1997.

More recent work by Parmantier in France has resulted in the CRIPTE code † †

– Presently being marketed commercially by ESI in France

• Both codes operate in the frequency domain and use numerical matrix inversion techniques to solve the BLT equation


The Topological Approach Has Been Used Extensively in the Past

Tesche, F. M, et. al., "Application of Topological Methods for Electromagnetic Hardening of the MX Horizontal Shelter System", LuTech, Inc. report prepared for Air Force Weapons Laboratory and Mission Research Corporation under Contract F29601-78-C-0082, January 1981.

Tesche, F. M., et. al., "Summary of Application of Topological Shielding Concepts to Various Aerospace Systems", LuTech, Inc. report prepared for Air Force Weapons Laboratory and Mission Research Corporation under Contract F29601-78-C-0082, February 1981

Tesche, F.M., "Introduction to Concepts of Electromagnetic Topology as Applied to EMP Interaction With Systems", NATO/AGARD Lecture Series Publication 144, Interaction Between EMP, Lightning and Static Electricity with Aircraft and Missile Avionics Systems, May 1986.

Parmantier, J. P., V. Gobin, and F. Issac, “Application of EM Topology on Complex Systems”, Proceedings of the 1993 IEEE EMC Symposium, Dallas, TX. August 1993.

Parmantier, J. P., et. al. “An Application of the Electromagnetic Topology Theory to the EMPTAC Test-Bed Aircraft”, Proceedings of the 6th FULMEN Meeting, Phillips Laboratory, November 29, 1993.


Application of Topology to System Design and Analysis

Topological concepts were used for the ground-up design of the Peacekeeper (MX) Missile system in the 1980’s.


Application of Topology to System Design and Analysis (con’t.)

Parmantier† has analyzed aircraft cabling in the 1990’s

† Parmantier, J-P, “First Realistic Simulation of Effects of EM Coupling in Commercial Aircraft Wiring”, IEE Computing & Control Engineering Journal, April 1998.

Aircraft and cable configuration Measured and computed voltages

Network topology



Overview



Summary


Role of EM Topology in the MURI Program

Provides the framework for decomposing a complex system into manageable “pieces”

Provides the methodology for integrating results from simple canonical problems (pieces) into the overall system response.

Helps to identify the appropriate interface location between the EM and circuit problems.


Interface Definition

A crucial decision is where to locate the interface between the EM and circuit problems

Shielded Enclosure with Equipment Topological Diagram

EM analysis at this point is relatively simple; circuit analysis down to the load equipment is more complicated

Incident EM Field

Load Equipment

Load Equipment

Incident EM Field

EM analysis at this point is much more complicated, with many interaction paths needed; however, the circuit analysis is at the load equipment is simpler.

An intermediate interface point is a compromise between the EM field analysis and the circuit analysis

A compromise is needed to decide on where the EM field/circuit interface will be located in the system analysis


Needed Extensions of EM Topological Methods Improvements are needed to the basic transmission line

models used for analysis using the BLT equation.– This is the basis for the “pieces” of the MURI project that

will be discussed later by other team members.

Extensions of the BLT equation to higher frequencies and for non-conducting propagation paths are needed.

Numerical implementation improvements are required.

These issues will be discussed in the following slides


Improvements to the Basic Transmission Line Models

Transmission line tubes entering into cavities, including the effects of cavity resonances

Random-lay transmission line tubes located over a ground or penetrating into an enclosure


Improvements to the Basic Transmission Line Models (con’t.)

Multiconductor tubes with a vertical run over a ground plane

Cross-coupling betweenmultiple tubes in a network


Extensions of the BLT Equation to Higher Frequencies

Include non-conductive paths in interaction sequence diagram– To model aperture or diffusive penetrations

Conventional BLT conducting interaction path

New, non-conductive BLT interaction path


Extensions of the BLT Equation to Higher Frequencies (con’t.)

Consider cross coupling between cables through apertures in enclosures

Treatment of multiple apertures in enclosures

Many other conductor and source configurations can be envisioned, and some will be discussed in other presentations for our MURI team


Improvements in Numerical Implementation

The solution of the BLT equation is numerically intensive– The main problem is the inversion of the matrix {[]-[S]}-1

Specific improvements to speed solution can include:– Implementation of fast matrix solvers

– Development and use of network reduction (collapsing) techniques

– Use of spectral estimation (interpolation) techniques

In addition, inclusion of norm measures in the BLT responses is desired

Development and implementation of the singularity expansion method (SEM) for BLT solvers is needed



Overview



Summary


Summary

Basic EM topological concepts have been reviewed and illustrated

The application of EM topology to the MURI project has been discussed– Provides a structured way of representing the EM interaction

process with complex systems

– Forms the basis for system decomposition into smaller “pieces”

– Aids in defining a suitable interface between the EM and the circuit-level analysis

– Provides a mechanism for computation, using the BLT formalism

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ELECTROMAGNETIC TOPOLOGY: ANALYSIS OF RF EFFECTS ON ELECTRICAL SYSTEMS

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