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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.

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  1. Update on the HPM Source and Effects Program at UMDJohn Rodgers, Mike Holloway (DEPS Scholar), Dr. ZeynepDilli,Mi Jung Jun, BisratAddissie and BipinGyawaliInstitute for Research in Electronics and Applied PhysicsUniversity of MarylandCollege Park, MD 20742rodgers@umd.edu

  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, IdoWaks Kristine Rosfjord, Dr. John Rodgers (PI) • Postdoc: Dr. ZeynepDilli • Graduate Students: Mike Holloway • Undergrads: • Mi Jung Jun (EE), BisratAddissie, BipinGyawali • 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. Scope of Work EM Coupling Cavity Fields Device Effects HPM Sources (multi-frequency) Circuit Effects Physical Models

  8. 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.

  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 containmodular components andstandardized 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= 1.284 GHz f= 1.502 GHz f= 1.591 GHz f= 1.654 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.

  19. Parasitic elements are then coupled to nonlinear circuit models Bond wire and package model Nonlinear IC model

  20. HPM Effects in Sensors & DetectorsApplications:Communications, Imaging, Ranging, Detection, Encoding IR PIN Photo Detector 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. 30-35, 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 0.9-1.4 GHz Pulse Width 100-500 s Helix terminated by plasma column produces dynamic EM boundary condition. The helix-plasma dispersion generates wideband chirps and hops in the output radiation.

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

  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 • 10-100 MW Power levels

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