The Workshop on Hybrid Formulations of Wave Propagat on and Scattering underwent a sequence of iterations before emerging in the format recorded here. These iterations were caused by various administrative and logistical problems which need not be detailed. However, its direction being set initially, the iterations led to modifications of the original concept so that the final form was arrived at through an indirect approach. This circumstance may ex plain some possible deficiencies which might have been removed, had the final concept been implemented directly. The motivation arose from a perception that the newly restored interest, coupled with new developments, in hybrid methods employ ing progressing wave fields and oscillatory wave fields for time harmonic and transient guided propagation in manmade or general geo physical environments, and for scattering by targets and irregulari ties, merits exposure to the wider scientific community. Accord ingly, a meeting with highly tutorial content was envisaged. For administrative reasons, related to sponsorship and organizational structure, this objective could not be realized but, eventually, there emerged the possibility of convening an Advanced Research Workshop (ARW) under the auspices of the NATO Advanced Study Insti tute Series. The original concept was then modified to accommodate a Workshop, wherein state-of-the-art science is discussed by a relatively small group of specialists, instead of tutorial presenta tions of more basic material."

The papers published in this volume were presented at the Second International Conference on Ultra-WidebandiShort-Pulse (UWB/SP) Electromagnetics, ApriIS-7, 1994. To place this second international conference in proper perspective with respect to the first conference held during October 8-10, 1992, at Polytechnic University, some background information is necessary. As we had hoped, the first conference struck a responsive cord, both in timeliness and relevance, among the electromagnetic community 1. Participants at the first conference already inquired whether and when a follow-up meeting was under consideration. The first concrete proposal in this direction was made a few months after the first conference by Prof. A. Terzuoli of the Air Force Institute of Technology (AFIT), Dayton, Ohio, who has been a strong advocate of time-domain methods and technologies. He initially proposed a follow-up time-domain workshop under AFIT auspices. Realizing that interest in this subject is lodged also at other Air Force installations, we suggested to enlarge the scope, and received in this endeavor the support of Dr. A. Nachman of AFOSR (Air Force Office of Scientific Research), Bolling Air Force Base, Washington, D.C.

Pulse Generation and Detection: Terahertz Radiation from ElectroOptic Crystals (X.C. Zhang et al.). Photoconductive Semiconductor Switches for High Power Radiation (G.M. Loubriel). Broadband Electronic Systems and Components: Pulse Generation and Compression on a TravellingWave MMIC Schottky Diode Array (M. Dragoman et al.). Precursor of an UltraWideband Radar System (A.S. Podgorski). Antennas and Arrays: Impulse Radiating Antennas (C.E. Baum, E.G. Farr). WideBandwidth Radiation from Arrays of Endfire Tapered Slot Antennas (D.H. Schaubert). Pulse Propagation and Guidance: Ultrashort Pulse Response in Nonlinear Dispersive Media (R. Albanese et al.). Modulation and Noise in Soliton Pulse Trains (J.M. Arnold). Scattering Theory and Computation: Phase Error Control for FDTD Methods (P.G. Petropoulos). Signal Processing Techniques: Stable Pole Extraction from Scattering Data (S.U. Pillai, T.I. Shim). 49 additional articles. Index.

In 1945, Dr. Ernst Weber founded, and was the first Director of, the Microwave Research Institute (MRI) at POLYTECHNIC UNIVERSITY (at that time named the Polytechnic Institute of Brooklyn). MRI gained world-wide recognition in the 50's and 60's for its research in electromagnetic theory, antennas and radiation, network theory and microwave networks, microwave components and devices. It was also known through its series of topical symposia and the widely distributed hard bound MRI Symposium Proceedings. Rededicated as the Weber Research Institute (WRI) in 1986, the research focus today is on such areas as electromagnetic propagation and antennas, ultra broadband electromagnetics, pulse power, acoustics, gaseous electronics, plasma physics, solid state materials, quantum electronics, electromagnetic launchers, and networks. Following the MRI tradition, WRI has launched its own series of in-depth topical conferences with published proceedings. The first conference was held in October, 1990 and was entitled Directions in Electromagnetic Wave Modeling. The proceedings of the conference were published under that title by Plenum Press. This volume constitutes the Proceedings of the second WRI International Conference dealing with Ultra*Wideband Short*Pulse Electromagnetics.

The Workshop on Hybrid Formulations of Wave Propagat~on and Scattering underwent a sequence of iterations before emerging in the format recorded here. These iterations were caused by various administrative and logistical problems which need not be detailed. However, its direction being set initially, the iterations led to modifications of the original concept so that the final form was arrived at through an indirect approach. This circumstance may ex plain some possible deficiencies which might have been removed, had the final concept been implemented directly. The motivation arose from a perception that the newly restored interest, coupled with new developments, in hybrid methods employ ing progressing wave fields and oscillatory wave fields for time harmonic and transient guided propagation in manmade or general geo physical environments, and for scattering by targets and irregulari ties, merits exposure to the wider scientific community. Accord ingly, a meeting with highly tutorial content was envisaged. For administrative reasons, related to sponsorship and organizational structure, this objective could not be realized but, eventually, there emerged the possibility of convening an Advanced Research Workshop (ARW) under the auspices of the NATO Advanced Study Insti tute Series. The original concept was then modified to accommodate a Workshop, wherein state-of-the-art science is discussed by a relatively small group of specialists, instead of tutorial presenta tions of more basic material.

The papers published in this volume were presented at the Second International Conference on Ultra-WidebandiShort-Pulse (UWB/SP) Electromagnetics, ApriIS-7, 1994. To place this second international conference in proper perspective with respect to the first conference held during October 8-10, 1992, at Polytechnic University, some background information is necessary. As we had hoped, the first conference struck a responsive cord, both in timeliness and relevance, among the electromagnetic community 1. Participants at the first conference already inquired whether and when a follow-up meeting was under consideration. The first concrete proposal in this direction was made a few months after the first conference by Prof. A. Terzuoli of the Air Force Institute of Technology (AFIT), Dayton, Ohio, who has been a strong advocate of time-domain methods and technologies. He initially proposed a follow-up time-domain workshop under AFIT auspices. Realizing that interest in this subject is lodged also at other Air Force installations, we suggested to enlarge the scope, and received in this endeavor the support of Dr. A. Nachman of AFOSR (Air Force Office of Scientific Research), Bolling Air Force Base, Washington, D.C.

Proceedings of the first WRI International Conference on [title] held October 1990, in New York, New York. The Weber Research Institute is the renamed (in 1986) Microwave Research Institute and will follow the MRI tradition of organizing topical meetings with published proceedings. Contributions dis