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
ELECTROMAGNETIC TOPOLOGY – Slide 3/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 4/32
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.
ELECTROMAGNETIC TOPOLOGY – Slide 5/32
Outline of Presentation
Overview
Introduction to EM Topology
Applications of Topology for the MURI Project
Summary
ELECTROMAGNETIC TOPOLOGY – Slide 6/32
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.)
ELECTROMAGNETIC TOPOLOGY – Slide 7/32
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.
ELECTROMAGNETIC TOPOLOGY – Slide 8/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 9/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 10/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 11/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 12/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 13/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 14/32
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)
External EM Environent
Power LinePenetration
Signal LinePenetration
InternalBarrier
(Equipment)
Internal EMEnvironment
DiffusivePenetrations
AperturePenetrations
Internal FieldCouplingSystem Response
EM Barrier (Shield)Conductor TransmissionField Transmission
Key
ExternalBarrier
(Facility)
External EM Environent
Power LinePenetration
Signal LinePenetration
InternalBarrier
(Equipment)
Internal EMEnvironment
DiffusivePenetrations
AperturePenetrations
Internal FieldCouplingSystem Response
EM Barrier (Shield)Conductor Transmission
Key
– A common low frequency approximation is to neglect the EM field couplings and treat only the conductors
ELECTROMAGNETIC TOPOLOGY – Slide 15/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 16/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 17/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 18/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 19/32
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.
ELECTROMAGNETIC TOPOLOGY – Slide 20/32
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.
ELECTROMAGNETIC TOPOLOGY – Slide 21/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 22/32
Outline of Presentation
Overview
Introduction to EM Topology
Applications of Topology for the MURI Project
Summary
ELECTROMAGNETIC TOPOLOGY – Slide 23/32
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.
ELECTROMAGNETIC TOPOLOGY – Slide 24/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 25/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 26/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 27/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 28/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 29/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 30/32
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
ELECTROMAGNETIC TOPOLOGY – Slide 31/32
Outline of Presentation
Overview
Introduction to EM Topology
Applications of Topology for the MURI Project
Summary
ELECTROMAGNETIC TOPOLOGY – Slide 32/32
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