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Wideband and ultrawideband (UWB) technologies have achieved notable progress in recent years, aided immeasurably by improvements in solid-state manufacturing, computers, and digitizers. As a result, wideband systems that were difficult or impossible to implement ten years ago are now being built for an increasingly wide variety of applications including transient radar, concealed object detection, mine clearing, pipeline inspections, archeology, geology, electronic effects testing, and communications. In this paper, we discuss current wideband source technology around the world as well as laboratory and test facilities. We also will briefly touch on frequency limitations of anechoic chambers, design of transmission line simulators, frequency regulation requirements for outdoor ranges, and personnel exposure limits. Index Terms--High-power microwaves, sources, test ranges, transient, ultrawideband.

In this paper, the analysis and design of an exponentially tapered transmission line antenna is presented. The exponentially tapered transmission line is designed to operate such that it has radiator characteristics at high frequency and serves as a matching section at low frequency. The NEC-2 is used to model the antenna at frequencies ranging from 500 MHz to 1 GHz to obtain the input impedance and the desired radiation pattern.

A newly developed solver (GLS3D) code, coupled with the existing EAGLE grid generation code, is used to numerically solve for the potential and charge distributions of a transmission line formed by two elliptical conductors. This technique employs the finite-difference solution using boundary fitted coordinates. Results obtained from this technique and the finite-difference technique with a rectangular grid are presented. Also, a comparison with theoretical results for circular and flat conductors is made to illustrate the validity of the technique.

Ultra-wideband (UWB) microwave sources and antennas are of interest for a variety of applications, such as transient radar, mine detection, and unexploded ordnance (UXO) location and identification. Much of the current research is being performed at the Air Force Research Laboratory (AFRL) at Kirtland AFB, NM. The approach to high power source development has included high pressure gas switching, oil switching, and solid-state-switched arrays. Recent advances in triggered gas switch technology and solid-state-switched shockline technology have opened up new possibilities for the development of much higher power systems and have thus opened the door to many new applications. The research into UWB transient antennas has also made significant contributions to the development and improvement of wideband continuous wave (CW) antenna designs and has brought new knowledge about the complex behavior of ferrites, dielectrics, and resistive materials in short pulse, very high voltage environments. This has in turn led to advances in the technology of transformers, transmission lines, insulators, and UWB optics. This paper reviews the progress to date along these lines and discusses new areas of research into UWB technology development. Index Terms--High power microwave, impulse-radiating antenna, oil switch, photoconductive solid-state switch, spark gap switch, transient antenna, ultra-wideband.

Triggered gas switches increase the reliability and repeatability of pulsed power systems. In particular, the performance of high-power, repetitively rated impulse generators is greatly enhanced by including a triggered switch. Impulse generators generally consist of cascaded energy storage elements, and the pulse-to-pulse voltage variations depend, to the first order, on the consistency of the voltage in the first energy storage stage. Thus, a repetitively operated trigatron has been developed to discharge a low-inductance, 70-J primary capacitor bank with very repeatable voltage at a pulse repetition frequency of 600 Hz. In order to simplify the pulsed power for mobile field-testing, it is desirable to seal the spark gaps to eliminate the need for a gas reservoir. Although high-pressure spark gaps have been sealed previously, long-term containment has not been pursued. To operate at high-pulse repetition frequencies, hydrogen, which is notoriously hard to seal at high pressures, must be used for its superior recovery properties. The hermetic seal was achieved by the careful selection of materials and fabrication techniques and designed for at least one year of use without refreshing. Index Terms--Repetitive operation, trigatron, triggered spark gap, voltage control.

This paper describes developments in high-altitude electromagnetic pulse (HEMP) test methods. More specifically, we describe the most commonly used HEMP test methods and associated measurement systems used to assess systems and equipment to the early-time (E1) effects of HEMP. Short case studies of the application of these test methods are included. Finally, computational electromagnetics (CEM) is a subject that has advanced significantly in recent years. This paper summarizes developments in this area and the supporting role that CEM has when undertaking assessments of the impact of HEMP on systems. [ABSTRACT FROM AUTHOR]

This paper investigates the possibility of using the impulse-radiating antenna (IRA) as both a transmitter and receiver of electromagnetic energy for the purpose of target identification. Of specific interest is estimating the induced open-circuit voltage at the IRA's source terminals, when it is illuminated by the scattered EM field from simple conducting bodies excited by an incident field from the same IRA acting as a transmitter. In this study, several different canonical scatters are considered, including thin wires, spheres, conducting boxes, and an infinite conducting plate. For a 7 kV pulse excitation of the IRA, received peak transient voltages at the antenna ranged from a few volts to about 400 volts, depending on the scatterer. [ABSTRACT FROM AUTHOR]