Effects of RF Pulses on Circuits and Systems – Pieces

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MURI Team Experience in EM Penetration and Coupling

Pieces

Effects of RF Pulses on Circuits and Systems – Pieces

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MURI Team Experience

Wires and

Apertures

Penetration Accuracy Enhancement

Coupling

Building

Penetration

Time Domain Methods

FDTD Fast

Methods

Integral Equations

Freq. Domain

Methods

Cavity Penetration

Block House Penetration

Backdoor Entry

Nonlinear Loads

Exterior Problems

Experimental Verification

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Wires, Apertures, Conducting Surfaces

• Wire through hole in conducting screen

• Wire excited through aperture in conducting screen

• Penetration through arrays of slots

• Wire-to-wire coupling through slot in screen

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Wire through Hole in Conductor

Effects of RF Pulses on Circuits and Systems – Pieces

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Wire through Hole in Conductor

Effects of RF Pulses on Circuits and Systems – Pieces

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Effects of RF Pulses on Circuits and Systems – Pieces

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co n s tan t

x

y

LIME excitation of vent slots

Effects of RF Pulses on Circuits and Systems – Pieces

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Wires coupled via a Slot in a Screen

Matched Coax

Z0

V0

BackSide Probe

Finite LengthNarrow Slot

RadiatingAntenna

Driven Coax

Metal Screens

Effects of RF Pulses on Circuits and Systems – Pieces

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x

z

2L =

2H a = / 2

2H w = / 2

d a = / 2

d w = / 2

a = 135 o

Effects of RF Pulses on Circuits and Systems – Pieces

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x

z

2L =

2H a = / 2

2H w = / 2

w = - 45 o

d a= / 2

d w = / 2

a = 135 o

Effects of RF Pulses on Circuits and Systems – Pieces

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Penetration into and Radiation from Enclosures through Apertures

• Penetration into box via slot in sidewall

• Penetration through loaded aperture

• Coupling to wire in slotted conducting tube

• Coupling to wire in box through slot in wall

• Wire in box with slots in sidewall -- EIGER

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Electric Field Shielding (dB): Validation of MLFMM code EMCAR

0 0.2 0.4 0.6 0.8 1-20

-10

0

10

20

30

40

50

Frequency in terms of GHz

Ele

ctr

ic F

ield

Sh

ield

ing

(d

B)

Electric Field Shielding vs. Frequency

MLFMMMeasured data

y

x

zEy

k

30 cm

30 cm

12 cm

Rectangular Aperture 20 by 3 cm

Measured at Center of cavity

Note that at resonance relative coupling is increased by 20dB as compared to ambient field

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Transmission Through Loaded Apertures

Transmission vs. Incidence Angle Transmission vs. Frequency

feed

e

r1

e

r2

e

r3

e

r4

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Coupling to a Wire Near a Slotted Cylinder

Infinite PECTube

Thin-WireAntenna

Narrow Slot

Infinite PECTube

Thin-WireAntenna

Narrow Slot

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Plane Wave Exciting Wire in Slotted Tube

b w h

aai

/ . , / . , / .

/ , / . ,

0 2 0 01 2 0 5

0 0 00091 0

Effects of RF Pulses on Circuits and Systems – Pieces

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Analysis of a Probe Inside a Slotted Cavity

x

y

a - a

- b

b

L - L

Z g

V g

()

()

PEC

Cavity

z

y

b

-b

Aperture

Original Problem( Valid everywhere )

Probe

Z g

V g

d

h

c

PEC Cavity

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Corroboration of Computed Data

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Results

• EIGER (preliminary results)

• Measurement (IEEE Trans. EMC, May 1994, pp. 144 -146)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0.4 0.45 0.5 0.55 0.6 0.65 0.7

Frequency (GHz)

No

rma

lize

d O

utp

ut

Cu

rre

nt

Normalized output current for a 1 V source

+ -

0.4 m

0.6 m

0.36 m

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Accurate Methods—Assurance of Accuracy

• Penetration into slotted rectangular tube – 2D

• Coupling to probe in nose cone of “mock” missile

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Weak Penetration Study

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Weak Penetration Study

Y G

I G

2d

2e

2c

2a

ahch

bh

2b

0 20 40 60 80 100 120 140 160 180 (degrees)

0

1E-006

2E-006

3E-006

4E-006

5E-006

6E-006

|E |

no

rm

closed-bodyscatterer method

short-cct curent methodaperture method

/ 0.1, ah e dl = ¹

Far-zone electric field due to the probe inside mock missile with partially closed nose cone: hc= 14.6 cm, hb= 118.7 cm, a= 0.0787 cm,

b= 7.875 cm, c= 0.2286 cm, d= 4.25 cm, e= 3.1 cm.

Effects of RF Pulses on Circuits and Systems – Pieces

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Penetration into Buildings

• Penetration through composite wall – concrete with rebar “shield”

• Composite transfer function

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Modeling of EM Field Penetration into Buildings

Concrete Layers (d, w , w , w )

Rebar Shield (wire radius r w

mesh spacing a w )

Equivalent shield

Computed Transmission (dB) Measured Transmission

• Simple models for field penetrations into complex facility walls have been developed, using previously measured

data

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Modeling of EM Field Penetration into Buildings (con’t.)

• Example of the transfer functions for a rebar shield alone, one and two layers of concrete (each 0.102 m thick with r = 1, r =

1, = 0.1 S/m), and the composite rebar/concrete shield.

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Time Domain Methods, Fast Methods

• Penetration through curved slots

• Fast time domain integral equation (TDIE) methods–penetration into enclosures

• “Low frequency” considerations of TDIE

• Accommodate nonlinear loads

• Finite difference time domain (FDTD) methods

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Curved Slot in Conducting Surface

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Penetration through Slotted Surface

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Rapid time domain analysis of motherboards/cards, (partial) enclosure, pins,…

• Approx. 10K spatial unknowns

• Broadband analysis = 2 hours

Fast TDIE analysis: EMC of enclosures

Effects of RF Pulses on Circuits and Systems – Pieces

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Fast TDIE analysis: EMC of enclosures (Cont)

Radiated power for different configurations

Pow

er

Pow

er

(dB

mW

)(d

Bm

W)

f (GHz)f (GHz)

• Ventilation slot emissions

17.5 cm 4.5 cm

25 cm25 cm

5 cm10 cm

1 cm

20 cm

30 cm

30 cm

15 cm

Chassis + motherboard +cards

Effects of RF Pulses on Circuits and Systems – Pieces

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Fast TDIE analysis: low frequency aspects

• Rapid time domain analysis of motherboards with traces, cables, gaps, etc

• Approx. 3K spatial unknowns

• Broadband analysis = 30 mins

• Using stable TDIE schemes

– Galerkin testing in time (Nedelec / Volakis)

– Loop star decompositions

• Contrary to FDTD: no timestep limitation (CFL >>> 1)

Effects of RF Pulses on Circuits and Systems – Pieces

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NA

Fast TDIE analysis: low frequency aspects (Con’t.)

2mm

30 cm

20 cm

60 cm

60 cm

Excitation fmax = 1 GHzExcitation fmax = 1 GHz

at fmax = 0.3 mat fmax = 0.3 mds at fmax = ds at fmax = /300 /300 /10/10 2707

SN

Comparison of computed |S21| Comparison of computed |S21| to the measured resultto the measured result**

-90

-80

-70

-60

-50

-40

-30

-20

-10

0.1 1

ALF-PWTDmeasurement

|S21

| (dB

)

frequency (GHz)

Effects of RF Pulses on Circuits and Systems – Pieces

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Fast TDIE analysis: nonlinear circuitry

We have developed a capability for analyzing lumped nonlinear elements in within TDIE framework.

1/0 0( ) ( )v i v i i

0 01000 V, 0.1 A

=30

v i

varistorsvaristors

-1 0 1-2

-1

0

1

2

Current (kA)

Vol

tage

(kV

)

0 0.5 10

10

20

30

40

50

Ma g

nitu

d e (

kV)

( )t s

0 0.02 0.04 0.06 0.08 0.1-0.4

-0.2

0

0.2

0.4

0.6

0.8

1 PWTD-line1PWTD-line2ref-line1 ref-line2

( )t s

Voltage on the varistorVoltage on the varistor

5 m5 m

0.1 m0.1 m 500 500 500 500

0.02 m0.02 m

k̂

excE

Effects of RF Pulses on Circuits and Systems – Pieces

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Finite Difference Time Domain (FDTD) Modeling

• Investigation of EM fields radiated from a localized sourceinside a buried facility

Earth surface

z

x

Ex componentplotted along this line

Vertical antennaL = 1.74 ma = 0.1 cm

Excitation voltagesource Vo(t)

+

0.7 m

Problem Geometry 3-Dimensional FDTD Model

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43

Cell no.

43

41

39

37

35

33

31

29

27

25

23

21

19

17

15

13

11

9

7

5

3

1

Region #1 - Free space

Region #2 - Earth

Region #3Concrete

Air-earth interface

Perfect conductor

(free space)

Cell no.

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Finite Difference Time Domain (FDTD) Modeling (Con’t.)

Tangential E-field at earth surface at t = 65.8 ns

0 2E-7 4E-7 6E-7 8E-7Tim e (s)

-8 .0E -5

-6.0E-5

-4.0E-5

-2.0E-5

0.0E+0

2.0E-5

4.0E-5

6.0E-5

8.0E-5

rE (t)

C ase 6 = 45 deg. = 0 deg.

rEcom ponent

rEcom ponent

Radiated E-field in far zone

Effects of RF Pulses on Circuits and Systems – Pieces

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The Exterior Problem, Fast Frequency Domain Methods

• Leakage of field from exterior to interior through cracks, seams, and holes

• Leakage of field from exterior to interior through antennas

• Fast frequency domain methods (FD) for “massive problems”

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EMI Threat to Aircraft SystemsAirborne Transmitter

Ground-based orship-board Transmitter

PEDSLightening

External Threat

• Coupling from other Aircraft Systems• Natural Environmental Effects (Lightening, Static Electricity)• Man Made Sources External to the aircraft (High Intensity Radiated Fields - HIRF)

Internal Threat

• Portable Electronic Devices (PEDS) carried by passengers

Picture from NASA-Langley

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Antenna Simulation on Full Scale Aircraft

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Coupling through Antennas

• Antennas are ‘doors’ to coupling from external excitations into the aircraft, tanks, missiles, ships, control centers, etc.

• For coupling studies, details such as wires, feed structures and loadings are crucial

Patch or array

Vout

feed

e

r1

e

r2

e

r3

e

r4