@article{6d1e26348f1444ccad79930d886b7f4d,
title = "Certain Considerations in Aperture Synthesis of Ultrawideband/Short-Pulse Radiation",
abstract = "We consider certain characteristics of the radiation from collimated, ultrawideband short-pulse aperture distributions. It is shown that an efficient radiation must account for the multifrequency nature of the field. Two alternative schemes for wideband aperture synthesis of an impulse-like radiation pattern are examined. The first, entitled the “Iso-width aperture,” utilizes only temporal shaping of the excitation pulse. In the other, the “Iso-diffracting aperture,” we suggest source shaping in spacetime so that all the frequency components in the field have the same collimation distance. The “iso-diffracting” scheme yields higher directivity and more efficient pulsed radiation. Explicit examples for the pulsed source distribution and for the pulsed radiation patterns are presented, parametrized, and contrasted.",
author = "Ehud Heyman and Timor Melamed",
note = "Funding Information: is the spatial spectrum of &(z. w). Here and henceforth, over-caretted coordinates are unit vectors and over-caretted field terms denote frequency domain constituents with a suppressed time-dependence exp( -zwt). The amplitude term in (1) con-tains a time-derivative term (-iw) which de-emphasizes the low-frequency components in the far zone. This term must be compensated in order to synthesize an impulse-like ra-diation pattern. Two alternative approaches are considered in Sections I1 and I11 below. In the first, entitled the “Iso-width aperture,” the compensation utilizes shaping of the temporal excitation pulse only. In the alternative approach, the “Iso-diffracting aperture,” we suggest source shaping in space-time. To construct this scheme we first explain the time-deriyative in (1) in terms of fundamental radiation mechanism and show that it is due to the frequency dependence of the aperture{\textquoteright}s Fresnel distance F(w). It therefore follows that synthesizing the aperture so that all frequency components will have the same Fresnel distance yields higher directivity and more efficient pulsed radiation. We also present and contrast explicit examples for the pulsed source distribution and for the resulting pulsed radiation patterns. The “iso-width{\textquoteright} aperture models several high-power pulsed radiation systems [8]-[ 101 (the so called impulse radiating antenna (IRA); e.g., - a quasi TEM horn). Realization of the Manuscript received June IO, 1993; revised October 25, 1993. This work “iso-diffracting” aperture requires an array of pulsed Sources Grant ~49620-93-1-0093 and in by the u,s..I~~~~i ~~~sci~ence~ is supported in part by the U.S. Air Force Office of Scientific Research under whose i ~amplitude ~ ~ distribution, l as well as the their initiation Foundation, Jerusalem, Israel, under Grant 88-00204. times and pulsewidths, should be tuned per the specifications The authors are with the Department of Electrical Engineering-Physical (e,g., the collimation). Possible candidates to realize this Israel. Electronics, Faculty of Engineering, Tel-Aviv University, Tel-Aviv 69978, distribution are the new optically triggered photoconducting IEEE Log Number antennas [11]-[I31 (see also articles in [l]). Some general",
year = "1994",
month = jan,
day = "1",
doi = "10.1109/8.286220",
language = "English",
volume = "42",
pages = "518--525",
journal = "IEEE Transactions on Antennas and Propagation",
issn = "0018-926X",
publisher = "Institute of Electrical and Electronics Engineers",
number = "4",
}