1. 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

2. Outline State of the UMD HPM Effects Research Group post-MURI
New Capabilities:
System for studying EM field and coupling statistics in complex cavities (AFOSR DURIP)
New sources:
7 kW pulsed L-band TWT w/ arbitrary waveform generator
MW wideband (chaotic), pulsed L-band source
New Efforts:
Radiation Studies
Mitigation Strategies
HPM Source Development

3. 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

4. New Experimental Systems & Capabilities
Pyramidal RF test chamber for coupling studies
Q-configurable test chamber and 7 kW pulsed TWT rack for radiation studies

5. New Experimental Systems & Capabilities
Upgraded RF probe station for studies of effects in electronic circuit boards
WB MW HPM Source

6. Research Goals
HPM Effects: Deterministic 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.

7. HPM Sources (multi-frequency)
Scope of Work
EM Coupling
Cavity Fields
Device Effects
HPM Sources (multi-frequency)
Circuit Effects
Physical Models

8. One Statistical Approach: RCM
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: sec. execution time.
Q: What about non-ideal (realistic) structures?
High Loss, large variations in boundary conditions
Examples: aircraft cockpit, vehicle compartments, rooms.

9. 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

10. Results: Q ~ 200
RCM
Experiment

11. Results: Q ~ 100
Short-orbit effects
RCM
Experiment

12. Results: Q ~ 50
Short-orbit effects
RCM
Experiment

13. Characterization of Electronic Enclosures
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.
LAN switch with coaxial RF ports
PC with waveguide port

14. 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 #2
Port #1
Strong resonances are observed across L-band (~1-2 GHz)

15. RF Surface Current Density for Various TEM Eigenmodes on the Motherboard
EMI Gasket
Power Supply
Power Bus
f= GHz
f= GHz
f= GHz
f= GHz

16. 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.

17. 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).

18. The EM characteristics of electrically small (d<l) features (IC packaging leads, bonding wires, etc.) can be extracted and modeled as lumped elements.
And can handle coupling, radiation and calculate the HF reactance of packaging and bond wires.

19. Parasitic elements are then coupled to nonlinear circuit models
Bond wire and package model
Nonlinear IC model
The extracted parasitics are imported as lumped element models into NL circuit simulator.

20. HPM Effects in Sensors & Detectors Applications: Communications, Imaging, Ranging, Detection, Encoding
IR PIN Photo Detector
A new wideband effects test system (funded by AFOSR DURIP) was put into operation in November ARL asked us to test infrared photodetector arrays (upper figures). We commenced testing of mixed-signal systems and sensors such as Hall effect probes, which are commonly used as position indicators in vehicles.
Hall Effect Sensor

21. Nonlinearity in TWT’s (1-D Model)
RF field on helix
Modulated electron beam
Over-modulation of the beam increases space-charge forces which saturate the amplifier.
Equation of Motion
Continuity
Gauss’s Law
Wave Equation

22. Numerical Results Using Quadratic Saturation Model
Surface of Section
System Parameters:
Return Map
2. V. Dronov, M. Hendry, T. M. Antonsen, Jr., and E. Ott, Chaos, Vol. 14, No. 1, pp , 2004.

23. Characteristics of 276HA TWT Amplifier for Satellite Communications
Frequency: 3-4 GHz
Output Power: 0.6 W
Gain: 35 dB
Bandwidth: 1 GHz
Efficiency: 70%
Phase becomes periodic for large input amplitudes!

24. TWT Loop Gain = 1.60

25. Development of Novel Wideband HPM Test Sources
Power 1-2 MW
Frequency GHz
Pulse Width s
Helix terminated by plasma column produces dynamic EM boundary condition.
The helix-plasma dispersion generates wideband chirps and hops in the output radiation.
AFOSR (Bob Barker) is sponsoring research on a wideband HPM source.

26. HPM source with chirp-hop output frequency
Frequency (MHz / 10)
Time (ms)
Loop Gain = 15 dB
Loop Gain = 5 dB

27. Evolution of HPM Power and Frequency
100 s
500 MHz
Total Power 1 MW

28. 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
MW Power levels