ELECTROMAGNETIC TOPOLOGY: ANALYSIS OF RF EFFECTS ON ELECTRICAL SYSTEMS

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ELECTROMAGNETIC TOPOLOGY ANALYSIS OF RF
EFFECTSON ELECTRICAL SYSTEMS

• F. M. Tesche
• Prepared UnderAFOSR MURI Grant with
• University of Illinois at Chicagoand
• Clemson University
• University of Houston
• University of Illinois at Urbana-Champaign
• University of Michigan
• June 13, 2001

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Outline of Presentation

• Overview

• Introduction to EM Topology

• Applications of Topology for the MURI Project

• Summary

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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
Digital Components
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Problem Statement (cont.)

• 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.

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Outline of Presentation

• Overview

• Introduction to EM Topology

• Applications of Topology for the MURI Project

• Summary

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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.)

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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.

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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
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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

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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

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Example of the Topological Approach

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

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Topological Representation of the Facility

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

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The Interaction Sequence Diagram Describes the
Entire Interaction Process

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

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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)

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

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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
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The BLT Equation A Solution for the
Transmission Line Network (cont.)

• 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

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The BLT Equation A Solution for the
Transmission Line Network (cont.)

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

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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

• 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

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.
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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.

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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 1980s.

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Application of Topology to System Design and
Analysis (cont.)

• Parmantier has analyzed aircraft cabling in the
  1990s

Aircraft and cable configuration
Measured and computed voltages
Network topology
Parmantier, J-P, First Realistic Simulation of
Effects of EM Coupling in Commercial Aircraft
Wiring, IEE Computing Control Engineering
Journal, April 1998.
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Outline of Presentation

• Overview

• Introduction to EM Topology

• Applications of Topology for the MURI Project

• Summary

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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.

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Interface Definition

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

Shielded Enclosure with Equipment
Topological Diagram
Incident EM Field
Load Equipment
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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
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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

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Improvements to the Basic Transmission Line
Models (cont.)

• Multiconductor tubes with a vertical run over a
  ground plane

• Cross-coupling betweenmultiple tubes in a
  network

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Extensions of the BLT Equation to Higher
Frequencies

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

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Extensions of the BLT Equation to Higher
Frequencies (cont.)

• 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

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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

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Outline of Presentation

• Overview

• Introduction to EM Topology

• Applications of Topology for the MURI Project

• Summary

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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