Effects of High-Power Microwave Pulses on Electronic Systems

August 1, 2008

Air Force Office of Scientific Research

A five-year program comprising several coordinated research efforts was devoted to increasing understanding and developing capabilities for computational modeling of the effects of high-power microwave (HPM) radiation upon electronic circuits and upon systems that comprise or include electronic circuits. The HPM radiation of primary interest in

this program included both narrow-band and ultra-wide-band (UWB) pulsed radiation. Whether aimed at electronic equipment deliberately or inadvertently, either type of radiation can, potentially, cause damage and/or adversely affect operation. The knowledge gained from this program can help in designing future electronic circuits and systems to be less vulnerable to damage and disruption by incident HPM/UWB radiation.

A Box With a Feed Wire that passes through a square hole on one side and is connected to an electronic circuit inside is a simple example of electronic systems and structures addressed in the research described in the text.

Key to the technical approach followed in this research is the concept of electromagnetic topology, according to which the problem of modeling a complex electromagnetic system is subdivided into smaller pieces that can be analyzed separately with high accuracy and efficiency. Each piece is treated as an N-port (where N is an integer) network and represented by a generalized scattering matrix. The electromagnetic coupling of all the pieces is modeled through the cascade of all the scattering matrices.

The major contributions of

this program include the following:

Capabilities for computational simulation of penetration and coupling of HPM/UWB radiation from exterior or interior sources into electronic systems and into structures that contain such systems were developed and were applied in sample problems. Examples of such structures include aircraft, ground vehicles, and equipment boxes with cracks, doors, and/or other apertures that may accommodate wires and/or antennas (see figure). Exterior and interior features of systems and of apertures through which electromagnetic radiation penetrates systems are taken into account. Following the electromagnetic-topology approach, a system is divided into many sub-systems (pieces), each of which can be analyzed thoroughly by any of several computer programs that solve the applicable electromagnetic-field equations by, variously, a frequency- domain integral-equation moment method, a hybrid finite-element method, or a time-domain integral-equation method.
Computer programs for simulating nonlinear and linear transient responses of digital circuits to penetrating HPM/UWB signals were developed. One of these programs is a network-oriented nonlinear- transient simulator based on a model that goes beyond the model embodied in the now-traditional Simulation Program with Integrated Circuit Emphasis (SPICE) general-purpose analog-integrated-circuit- simulating software. This program accounts for the distributed electromagnetic nature of coupling paths, and of components having sizes that are significant fractions of wavelengths, while fully accommodating both small-signal and large signal models of nonlinear electronics. Another program implements electrical- circuit models for coupling paths to be used in the nonlinear-transient simulator. A third program affords an electromagnetic- modeling capability for converting the radiated and conducted electromagnetic interference signals into a set of noise sources to be used in the nonlinear-transient simulator. An important feature of this development is separation of the electromagnetic-field analysis from the nonlinear-circuit analysis, with the understanding that the dimensions of electronically nonlinear components are much smaller than the smallest wavelengths of electromagnetic interference.
Analyses of responses of selected digital circuits and systems to incident HPM/UWB signals, by means of nonlinear transient simulations, were performed in an effort to gain high-level understanding of the effects of HPM/UWB signals on the behaviors of such circuits and systems. Effects of interest included alterations of components of the circuits and alterations of digital logic states (bit errors). SPICE and the nonlinear- transient-simulating programs described above were used in these analyses.
In recognition of the approximate nature of computational simulations, an effort was devoted to development of capabilities and methods for validation of the various models and simulation capabilities summarized above. This included efforts to develop theoretical, experimental, and computational capabilities for assessing the accuracy of numerical data from selected subsets of pieces of computationally modeled systems. The fruits of this effort include several exact solutions for penetration of signals into, and radiation and scattering of signals from, bodies having simple shapes.

This work was done by Piergiorgio L. E. Uslenghi, Erricolo, Danilo, Hung Yu David Yang, and Shantanu Dutt of the University of Illinois at Chicago; Michael A. Bridgwood, Chalmers M. Butler, Anthony Q. Martin, and Frederick M. Tesche of Clemson University; Donald R. Wilton and David R. Jackson of the University of Houston; John L. Volakis of Ohio State University; Andreas C. Cangellaris of the University of Illinois at Urbana Champaign; and Pinaki Mazumder, Eric Michielssen, and V. V. Liepa of the University of Michigan for the Air Force Office of Scientific Research.

AFRL-0094