ELECTROMAGNETIC TOPOLOGY: ANALYSIS OF RF EFFECTS ON ELECTRICAL SYSTEMS

F. M. Tesche

Prepared Under AFOSR MURI Grant with

University of Illinois at Chicago and Clemson University University of Houston University of Illinois at Urbana-Champaign University of Michigan June 13, 2001

Outline of Presentation



Overview



Introduction to EM Topology



Applications of Topology for the MURI Project



Summary ELECTROMAGNETIC TOPOLOGY

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Slide 2/32

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

Parabolic dish reflector

Incident EM Fields

E ex Conical transmission line feed structure Source generator H ex Matching impedances

Illuminated System Internal Circuitry

Commercial Power KEY HEMP Shielding HEMP Filters MOVs UPS ROC Power Distribution Primary Power HEMP Filters Conduit AUX Port Pallet Power Distribution Box AUX Port Conduit Power Cable Air Conditioner Power Cable Conduit (Open To Radome) Conduit

Radome Enclosure

Utility Outlet Power Line AC/DC Converter Heater HEMP Hardened SCAMP (GFE) External Pwr Supply HEMP Enclosure Control Sensor Logic Card Fiber Mux Temp Controls Power Cable

ROC Circuit A1

HEMP Enclosure AC/DC Converter

Pallet

Standard 19" Rack (Unshielded) Power Cable Power Cable HEMP Hardened GFE Computer HEMP Hardened Control Status Logic Card Fiber Mux Growth Capability GFE Printer KIV-7 GFE Power line Communication line

Requirement is to determine behavior of the digital circuitry to the EM excitation ELECTROMAGNETIC TOPOLOGY

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Slide 3/32 Digital Components

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.

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Outline of Presentation

 Overview 

Introduction to EM Topology

 Applications of Topology for the MURI Project  Summary

ELECTROMAGNETIC TOPOLOGY

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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.)

ELECTROMAGNETIC TOPOLOGY

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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.

ELECTROMAGNETIC TOPOLOGY

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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: Physical Configuration

Topology is a key element to the model development

System Topology Electrical Model Maxwell's Equations “Back of Envelope ” Hybrid Methods Analytical Solutions Transmission Line Methods Discrete Methods Geometrical Optics, etc.

Integral Equations

ELECTROMAGNETIC TOPOLOGY

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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.

ex E H ex panel Weatherhead Conduit C line

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Topological Representation of the Facility

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

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

Ext er nal EM Envir onent Aper tur e Penetr ations

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

Diffusive Penetr ations Power Line Penetr ation Signal Line Penetr ation Exter nal ( Facility) In te r n a l B a r r ie r ( E q u ip m e n t) S y s te m R e s p o n s e

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

In te r n a l F ie ld C o u p lin g

Key

EM Bar r ier ( Shield) Conduct or Tr ansm ission Field Tr ansm ission Bar r ier Penet r at ion EM Field Point Field Excit at ion Response Locat ion

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

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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 P u ls e P o w e r P r o d u c tio n

S O U R C E

Wa v e fo rm S h a p in g E M F ie ld R a d ia tio n fr o m A n te n n a E M In te ra c tio n w ith S y s te m E x te rio r C u rr e n t In je c tio n C o u p lin g to C o n d u c to r s

C O U P L IN G

D iffu s iv e P e n e tr a tio n A p e rtu re P e n e tr a tio n E M F ie ld C o u p lin g to In te r n a l C o n d u c to r s C o n d u c to r P e n e tr a tio n

P E N E T R A T IO N

In te r n a l C o n d u c to r P r o p a g a tio n In te r n a l E q u ip m e n t E x c ita tio n

IN T E R N A L C O U P L IN G R E S P O N S E S

D a m a g e T h r e s h o ld s E q u ip m e n t R e s p o n s e s E q u ip m e n t F a ilu re E q u ip m e n t U p s e t N o E ffe c t

ELECTROMAGNETIC TOPOLOGY

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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 Field Transmission

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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

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

Z L Z L Z L

I inc I sca I I +

Z L Z L

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

Reference Conductor

† 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 ELECTROMAGNETIC TOPOLOGY

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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

Supermatrix multiplication

 

L



Y

   

c



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

  

  



 1 :

Voltage scattering supermatrix for all nodes Source supervector containing the excitations of each transmission line Propagation tube supermatrix for all tubes (suitably re ordered) ELECTROMAGNETIC TOPOLOGY

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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  

L





      



 1 :

ELECTROMAGNETIC TOPOLOGY

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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 1980’s.

ELECTROMAGNETIC TOPOLOGY

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

 Parmantier

†

has analyzed aircraft cabling in the 1990’s

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 Incident EM Field Load Equipment Topological Diagram Load Equipment Incident EM Field



A compromise is needed to decide on where the EM EM analysis at this point is relatively simple; circuit analysis field/circuit interface will be located in the system down to the load equipment is more complicated analysis equipment is simpler. ELECTROMAGNETIC TOPOLOGY

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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 ELECTROMAGNETIC TOPOLOGY

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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

ELECTROMAGNETIC TOPOLOGY

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

 Multiconductor tubes with a vertical run over a ground plane  Cross-coupling between multiple tubes in a network

ELECTROMAGNETIC TOPOLOGY

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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

New, non-conductive BLT interaction path Conventional BLT conducting interaction path ELECTROMAGNETIC TOPOLOGY

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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

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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 ELECTROMAGNETIC TOPOLOGY

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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

“pieces” into smaller – 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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