Publications (5)2.2 Total impact

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    D.V. Giri · J.M. Lehr · W.D. Prather · C.E. Baum · R.J. Torres
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    ABSTRACT: Previously, the design, fabrication, and testing of a pulser with a parabolic reflector antenna, known as a prototype impulse-radiating antenna (IRA), had been presented in the IEEE Transactions on Plasma Science in 1997. The radiating system has now been more fully characterized with additional measurements and computations of near-field, intermediate, and far fields on bore sight
    Full-text · Article · Nov 2000 · IEEE Transactions on Plasma Science
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    ABSTRACT: 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
    No preview · Article · Nov 2000 · IEEE Transactions on Plasma Science
  • D.V. Giri · C.E. Baum · J.M. Lehr · W.D. Prather · R.J. Torres
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    ABSTRACT: Previously, the design, fabrication and testing of a pulser with a parabolic reflector antenna, known as the prototype impulse-radiating antenna (IRA) has been presented. The paraboloidal reflector was fed by a TEM structure that in-turn was energized by a ±60 kV, ~100 atm. hydrogen switch operating in a burst mode at up to 200 Hz. The TEM structure also incorporated an electromagnetic lens to ensure a near-ideal spherical TEM wavelaunch. Some of the measured characteristics of this system were: (a) a peak electric field on boresight of 4.2 kV/m at a range r=305 m; (b) an uncorrected pulse rise-time (10-90%) of 99 ps; and (c) a boresight electric fields FWHM of 130 ps. The radiating system has now been more fully characterized with additional measurements and computations of near field, intermediate and far fields on the boresight. While the far fields from such a radiating system have been known for some time, the intermediate field analysis was only published recently. This method substitutes the radiated field from a paraboloidal reflector by the radiation field from the TEM structure reflected in the parabolic mirror. Although this work is limited to fields on the boresight at any distance from the antenna, the authors have been able to extend the analysis to the frequency domain. It has also been verified that the intermediate fields asymptotically tend to the far-field expressions, as the range r is increased. Good agreement between calculated and measured fields has been obtained for the prototype IRA in the near (r=5 m) and in the far field (r=305 m)
    No preview · Conference Paper · Feb 1999
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    [Show abstract] [Hide abstract]
    ABSTRACT: 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, USA. 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.
    Full-text · Conference Paper · Feb 1999
  • Source
    J.M. Lehr · C.E. Baum · W.D. Prather · R.J. Torres
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    ABSTRACT: For future applications, the limit of spark gap technology for ultrafast switching is explored. Specifically, an estimate of the fastest risetime achievable with a single channel spark gap has been investigated using three approaches. The first examines the growth of the electron avalanche in gases to estimate its growth rate. The avalanche growth rate determines the fastest possible risetime of the resultant pulse. The second approach uses the components of the velocity of electromagnetic propagation to estimate the achievable risetime. The third uses an equivalent circuit of a single channel spark gap to calculate the maximum achievable rate of voltage rise. The first two estimates indicate that risetimes on the order of 1-10 ps are achievable. The last treatment, however, illustrates the dependence of the pulse risetime on the peak voltage and calculates the maximum rate of voltage rise to be on the order of 10<sup>16</sup> V/s. To reduce the effect of the intrinsic inductance of the channel, a simple geometrical alteration to the spark gap geometry has been devised which effectively reduces the inductance per unit length of the spark gap to that of its transmission line feed. This simple change alleviates the constraint imposed by the maximum rate of voltage rise and is anticipated to permit the realization of picosecond risetime high power electromagnetic sources
    Full-text · Conference Paper · Feb 1998