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

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

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

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

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

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.

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

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: 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.

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

Results: Q ~ 200 RCM Experiment

Results: Q ~ 100 Short-orbit effects RCM Experiment

Results: Q ~ 50 Short-orbit effects RCM Experiment

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

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)

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

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.

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).

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.

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.

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 2008. 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

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

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.

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!

TWT Loop Gain = 1.60

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. AFOSR (Bob Barker) is sponsoring research on a wideband HPM source.

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

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

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