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26 Οκτ 2013 (πριν από 3 χρόνια και 1 μήνα)

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IREAP

Update on the HPM Source and
Effects Program at UMD


John
Rodgers,
Mike
Holloway (DEPS Scholar),
Dr.
Zeynep

Dilli
,

Mi Jung Jun,
Bisrat

Addissie

and
Bipin

Gyawali


Institute for Research in Electronics and Applied Physics

University of Maryland

College Park, MD 20742


rodgers@umd.edu

IREAP

Outline

1.
State of the UMD HPM Effects Research Group post
-
MURI

2.
New Capabilities:

a.
System for studying EM field and coupling statistics in
complex cavities (AFOSR DURIP)

b.
New sources:


7 kW pulsed L
-
band TWT w/ arbitrary waveform
generator


MW wideband (chaotic), pulsed L
-
band source

3.
New Efforts:

a.
Radiation Studies

b.
Mitigation Strategies

c.
HPM Source Development

IREAP

State of the UMD HPM Effects Group


Full time faculty:

Profs. Vic
Granatstein
,
Ido

Waks

Kristine
Rosfjord
, Dr.
John Rodgers (PI)


Postdoc
: Dr.
Zeynep

Dilli


Graduate Students: Mike Holloway


Undergrads:

Mi Jung Jun (EE),
Bisrat

Addissie
,
Bipin

Gyawali


Funding: AFOSR $100k/year, SNL $100k, DURIP $270k
(2008)


Notable increase in student interest in advanced EM & HPM
research

IREAP

New Experimental Systems & Capabilities

Q
-
configurable test chamber and 7 kW
pulsed TWT rack for radiation studies

Pyramidal RF test chamber for
coupling studies

IREAP

New Experimental Systems & Capabilities

Upgraded RF probe station for studies
of effects in electronic circuit boards

WB MW HPM Source

IREAP

Research Goals


HPM Effects
:
D
eterministic or hopelessly stochastic
processes?


Circuit Effects (deterministic)
:


Investigate nonlinear (overdriven), high frequency (out
-
of
-
band) response of devices, circuits & networks


Develop deterministic effects models that scale with
process technology


Modeling (combination):


EM Statistical
: Large
-
scale (rooms, buildings, vehicles,
etc) require statistical electromagnetic approach (RCM)


EM Finite Element
: Circuit
-
level coupling, parasitic
effects, HF resonances


Future Prospect
: A comprehensive, scalable approach to
modeling HPM effects.

IREAP

Scope of
Work

HPM Sources
(multi
-
frequency)

EM Coupling

Cavity Fields

Circuit Effects

Device Effects

Physical Models

IREAP

Prof. Steve
Anlage

One Statistical Approach: RCM


Solves field statistics based on GOE
(time
-
reversal symmetric) of chaotic
ray trajectories


Has been benchmarked for High
-
Q,
ideal structures


Minimal information about the target
required: estimates of volume & Q


Fast: 30
-
60 sec. execution time.

Q: What about non
-
ideal (realistic) structures?


High Loss, large variations in boundary conditions


Examples: aircraft cockpit, vehicle compartments, rooms.

IREAP

Test RCM for Non
-
Ideal Cavities with 20 < Q < 500


Configure test chamber
with many irregular
scattering surfaces


Place non
-
uniform loss
along boundaries


Measure EM statistics

IREAP

Results: Q ~ 200

Experiment

RCM

IREAP

Results: Q ~ 100

Experiment

RCM

Short
-
orbit effects

IREAP

Results: Q ~ 50

Experiment

RCM

Short
-
orbit effects

Characterization
of E
lectronic Enclosures

LAN switch with coaxial RF ports

PC with waveguide port



Most electronic systems
contain
modular components
and
standardized
form factors (4U, 19” bays, ATX, etc.)


Deterministic or statistical EM method?


The enclosures are clearly natural microwave
resonators with


~ D
.

Results of S
-
parameter measurements in
a
LAN switch



Port #1 is a dipole launching antenna and port #2 is connected to the main
+12 VDC power bus on the motherboard

Port #1

Port #2



Strong resonances are observed across L
-
band (~1
-
2 GHz)

RF Surface Current Density for Various TEM
Eigenmodes

on the Motherboard

f= 1.284 GHz

f= 1.502 GHz

f= 1.654 GHz

f= 1.591 GHz

Power
Supply

Power Bus

EMI Gasket

Results from Upset Studies in a LAN Switch


At upset, the RF caused the switching power supply to either completely
shut down or output the incorrect voltage for times that were 100


1000
times the RF pulse width.


This forced the microcontroller to completely reboot the system.

IREAP

Schematic of
LAN switch
power
regulator

Rectified RF voltage at
the feedback pin fools
the comparator into
detecting an over
-
voltage condition. It
then sends a shutdown
signal to the power
controller via an opto
-
isolator

The power controller feedback is
designed to shutdown the system (~
30 sec) even if the “fault” is
momentary (microseconds).

IREAP

The EM characteristics of electrically small (d<

)
features (IC packaging leads, bonding wires, etc.) can
be extracted and modeled as lumped elements.

IREAP

Parasitic elements are then coupled to nonlinear
circuit models

Bond wire and
package model


Nonlinear IC model

IREAP

HPM Effects in Sensors & Detectors

Applications:

Communications, Imaging, Ranging, Detection, Encoding

IR PIN Photo Detector

Hall Effect Sensor

Nonlinearity in TWT’s (1
-
D Model)

RF field on helix

Modulated electron beam

Equation of Motion

Continuity

Gauss’s Law

Wave Equation

Over
-
modulation
of the beam
increases space
-
charge forces
which saturate
the amplifier.

Numerical Results Using Quadratic Saturation Model

2.
V. Dronov, M. Hendry, T. M. Antonsen, Jr., and E. Ott,
Chaos,
Vol. 14, No. 1, pp. 30
-
35, 2004.

Surface of Section

Return Map

System
Parameters:

IREAP

Characteristics of 276HA
TWT
Amplifier

for Satellite Communications

Phase becomes periodic for large input amplitudes!

Frequency:

3
-
4
GHz

Output Power:

0.6 W

Gain:


35 dB

Bandwidth:

1 GHz

Efficiency:

70
%

TWT Loop Gain
= 1.60

IREAP

Development of Novel Wideband HPM Test Sources

Power


1
-
2 MW

Frequency

0.9
-
1.4 GHz

Pulse Width

100
-
500
m
s


Helix terminated by plasma
column produces dynamic
EM boundary condition.


The helix
-
plasma
dispersion generates
wideband chirps and hops
in the output radiation.

IREAP

Frequency (MHz / 10)

Time (
m
s)

Loop Gain = 15 dB

Frequency (MHz / 10)

Loop Gain = 5 dB

Time (
m
s)

HPM source with chirp
-
hop output frequency

IREAP

Evolution of HPM
Power and
Frequency

100
m
s

500 MHz

Total Power 1 MW

IREAP

Conclusions


RF rectification by ESD protection diodes and parasitic resonances have
been identified as major susceptibility issues.


The RF characteristics of these devices can be accurately described
using lumped
-
element circuit models with simple high
-
frequency diode
parameters.


Upset can be easily predicted in terms of the high
-
frequency transfer
characteristics of the circuit and the RF voltage, frequency and
modulation at the circuit terminals.


In systems, the problem requires an EM or RCM treatment.


Power controllers with feedback have been identified as a major and
universal problem.


An informed basis for developing effects sources:


L
-
band


Wideband or chaotic modulation


10
-
100 MW Power levels