By Topic

Ultra-Wideband Short-Pulse Electromagnetics 4, 1998

Date 14-19 June 1999

Filter Results

Displaying Results 1 - 25 of 50
  • Ultra- Wideband Short-Pulse Electromagnetics 4 (IEEE Cat. No.98EX112)

    Save to Project icon | Request Permissions | PDF file iconPDF (210 KB)  
    Freely Available from IEEE
  • Author index

    Page(s): 457 - 458
    Save to Project icon | PDF file iconPDF (75 KB)  
    Freely Available from IEEE
  • Large current radiator for the short electromagnetic pulses radiation

    Page(s): 149 - 155
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    One of the most important problems in modern ground penetrating radar design is creating the ultra wide band (UWB) antennas for short sounding electromagnetic pulses (SP) radiation. One of the promising UWB/SP radiators is the Large Current Radiator (LCR). This report discusses the performance of an improved design of a LCR View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new broad band resistive wire antenna for ultra-wide-band applications

    Page(s): 157 - 164
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    This article presents the theoretical analysis and the experimental results of a wire antenna. The wire antenna has been particularly designed to illuminate complex targets with an electromagnetic impulse. The aim of the study is to realise a low frequency (200 MHz-1.2 GHz) Radar Cross Section (RCS) measurement facility in the time domain. Then, not only the antenna has been designed to radiate and to receive short pulses without distortion but also to illuminate the test zone with an homogeneous and uniform electric field. The antenna must be fairly directive with maximum field in the axial direction View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • About mechanism of wideband microwave radiation at explosion of condensed high explosives

    Page(s): 33 - 39
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    The essence of the offered mechanism consists of the following: during expansion of products of detonation a highly non-equilibrium medium is generated, the oscillatory temperature of which can essentially exceed the rotational one. Such a medium is basically active from the point of view of generation and amplification of microwave radiation. As against laser active media, the frequency of collision of molecules is about the frequency of radiation, therefore the radiation will be wideband. As the air behind a shock wave is strongly ionized, the radiation can leave the explosion zone boundaries only after the decrease of this ionization because of its expansion and instability of border of detonation products. Presence of a shell as a way of initiation of the charge can accelerate process of destruction of a conducting layer behind a shock wave View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multichannel antenna systems for radiation of high-power ultrawideband pulses

    Page(s): 181 - 186
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    To realize attractive possibilities of ultrawideband (UWB) radars, it is necessary to develop multichannel antenna systems for radiation and control by characteristics of high-power electromagnetic pulses localized in space and time. In this paper, new results of single combined antenna investigations are presented. However, the main consideration is given to the investigation of interaction of combined radiators and plane electrical monopoles in linear arrays including the investigation under conditions of steering by the wave beam. Possibility to synthesize the electromagnetic pulse in free space in order to expand radiation spectrum has been investigated theoretically View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Calorimetric spectrometer for measuring single microwave pulses in relativistic microwave electronics devices

    Page(s): 41 - 47
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    Broadband plasma relativistic microwave oscillators fabricated at the General Physics Institute of the Russian Academy of Sciences have the following output parameters: microwaves are generated in a frequency band on the order of the mean frequency, the output power is -100 MW, the mean microwave frequency is 10-20 GHz, the duration of a single pulse is 20-800 ns, and the diameter of the emitting horn window is no less than 15 cm (because of the possible microwave breakdown). The spectrum of high-power broadband emission from the plasma in the course of a REB-plasma interaction was studied in experiments in a number of experiments but accuracy of measurement has been low. The authors describe a calorimetric spectrometer that has very high accuracy. The main advantage of the spectrometer is that it can measure the spectrum of the total microwave energy flux in absolute units, while the spectrometers used previously were capable of measuring only a small fraction of the total energy flux. The spectrum of the total energy flux from oscillators is the fundamental characteristic calculated theoretically and used to estimate the possible applications View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Numerical and measurement based study of the resonance frequency technique to detect anti-personnel mines

    Page(s): 417 - 424
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    The simulations show that it is useful to explore this technique further towards a practical design. Currently some first experiments seem to support some of the findings from FDTD simulations. We have identified a number of practical problems with the laboratory measurements that need to be tackled. We need to find an optimum polarization state that enhances the presence of buried man-made objects (symmetric). A combination of both imaging and extraction of natural frequencies information needs to be defined. We think that laboratory measurements under controlled conditions is a key issue in the establishment of the practical limitations of the proposed techniques View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Pulsed beam propagation in lossless dispersive media

    Page(s): 277 - 288
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    Concerns the parameterization of the effects of frequency dispersion on the propagation characteristics of a paraxially approximated pulsed beam (PB) wavepacket in a lossless medium with generic wavenumber profile. Various nondimensional measures-critical parameters-have been defined in order to systematically assess and quantify: a) the effect of dispersion on various observables associated with the PB field and thereby on the resolution of these observables; and b) the range of validity of the paraxial approximation under these conditions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultrawideband electromagnetic pulse propagation in triply-distilled water

    Page(s): 265 - 276
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    The observed dynamical field evolution due to an input ultrawideband electromagnetic pulse as it propagates through a complex dispersive medium is primarily due to the causal model components of the dielectric permittivity dispersion that is spanned by the bandwidth of the input pulse, The various model components of a given dispersive medium may then be probed individually by a properly designed ultrawideband pulse so that, by varying the carrier frequency of the input pulse, different features may be studied and their associated parameter values may possibly be extracted. An ideal pulse for this purpose is the rectangular envelope modulated signal since it is always ultrawideband even though it may not be ultrashort, The initial pulse width may then be tailored so that its spectrum may sample any desired feature in the dielectric dispersion of the chosen material View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Intermediate field of an impulse-radiating antenna

    Page(s): 77 - 89
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    Methods for evaluating the intermediate field are examined. The contour integrals for thin-wire TEM aperture distributions can be expressed in closed form. Other types of TEM fields are also of interest (e.g., for coplanar plates). It is suggested that the aperture need not be a circular disk (e.g., a semicircular disk, as in a half impulse radiating antenna). It was assumed that the TEM fields on the aperture are propagating parallel to the aperture normal. This need not be the case. One can assume that the aperture fields take the form of a TEM plane wave propagating in other directions. The results apply to only one part of the waveform, the “impulsive” part. For a reflector impulse radiating antenna one needs to include the prepulse associated with the TEM field View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Demonstration of submillimeter radiation generation from static field by superluminous ionization front in semiconductor capacitor array

    Page(s): 27 - 32
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    Generation of frequency upshifted monochromatic radiation in the 100 GHz to FIR range by the interaction of a superluminous photoconducting front with an electrostatic “frozen wave” configuration in a semiconductor is reported. The interaction converts the energy contained in the “frozen wave” into monochromatic radiation, whose frequency depends on the energy in the laser pulse creating the superluminous front and the wavelength of the static wave. Monochromatic free space propagating waves with frequency between 100 GHz and 1.6 THz were generated using a 100 fsec Ti:sapphire laser pulse incident obliquely on a ZnSe photoconducting slab containing a frozen wave field. A superluminous photoconducting front was formed by two photon absorption. Tunability was achieved by varying the laser pulse energy from .1 to 1 mJ. The electric field waveform of the emitted radiation pulse was measured by an optically gated miniature dipole antenna. The concept can be scaled to develop narrowband, tunable and powerful THz and FIR sources for spectroscopic imaging and other applications View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Direct construction of a ξ-pulse from natural frequencies and evaluation of the late-time residuals

    Page(s): 349 - 360
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    An important type of target identification utilizes the natural frequencies of the target, these being poles in the complex-frequency s-plane as expressed in the singularity expansion method. Since the location of these natural frequencies sα in the s-plane is aspect independent, this simplifies the identification problem to the comparison of the target pole patterns stored in some target library. In order to implement the pole pattern as a target discrimination scheme one needs some scheme to find the sα in experimental data (scattered fields), either explicitly or implicitly. Some of the early schemes used what is referred to as the Prony method in which one fits a sum of dumped sinusoids to a waveform. This had various limitations which have been overcome to some degree by a matrix pencil method. These and related techniques are explicit in that they determine a set of sα from one or more waveforms which are then compared to the target library. In contrast, implicit methods do not generate a set of sα from the data, but utilize predetermined sets of sα for various targets which are then manipulated with the data in some way which transforms it to a form in which the discrimination can be more readily performed. Those used to date have used temporal functions with two-sided Laplace transforms with zeros corresponding to the sα (poles) of preselected targets. Convolving these with target impulse response removes (annihilates) the late-time response for the properly chosen target. These go by various names such as K-pulse and E-pulse. In the present paper we go further into this latter type of target identification View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Summary of the DARPA background clutter data collection experiment

    Page(s): 409 - 416
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    Most technologies in use or proposed for use to detect landmines and unexploded ordnance (UXO) suffer from unacceptably high false-alarm rates, even at modest probabilities of detection. High false-alarm rates are a consequence of the inability to discriminate real UXO and landmines from man-made and naturally occurring clutter. Experimental data on expected signatures of UXO and landmines have been collected by various sensor developers and research agencies. However, an equivalent characterization of clutter returns has been lacking. As a result, background signatures have not been considered in sensor or algorithm design. The goal of the two-phase, DARPA-sponsored background clutter data collection experiment is to begin to fill this void. The first phase, completed during the fall of 1996, consisted of high aerial density site surveys using the following sensor types: magnetometer, infrared, electromagnetic induction, and ground-penetrating radar. The second phase, which is currently underway, consists of analysis of the collected sensor data to include excavation of clutter objects. This paper describes the clutter data collection program and provides a cursory summary of the analysis done to date View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultra-wideband duplexers for low and high peak power applications

    Page(s): 187 - 193
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (272 KB)  

    Two different duplexers have been conceived, designed and tested that allow for using an impulse ultra-wideband (UWB) radar in a monostatic configuration. The first one, which is based on a fast GaAs SPDT switch, is usable with a low peak power transmitter (<100 mW), while the second one, completely passive, is intended for high peak power applications (up to 50 kW). Both exhibit an instantaneous bandwidth covering the frequency range (400 MHz-4 GHz) which is the most suitable frequency band for detecting buried antipersonnel landmines by means of UWB radar. These duplexers contribute to a gain of space, weight and cost, three important factors in the design of portable detection systems for humanitarian operations View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A mixed time-frequency-scale analysis of the hybrid wavefront-resonance representation

    Page(s): 361 - 370
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    Several time-frequency-scale processing schemes for the analysis of short pulse scattering fields are explored and calibrated in connection with the problem of reflections from multilayered dispersive media. The time-frequency signature consists of a (generally nonuniform) grid of wavefront arrivals and resonances. It is shown that the time-frequency resolution is bound by the unit-cell area, hence the signature of a particular wave process can be detected only if the processing windows are scale-matched to corresponding unit cells. The short-time Fourier transform (STFT) has therefore an inherent limitation because it has a built in scale, while the wavelet transform with a Morlet wavelet provides a framework that adapts to all scales with no a-priori information while retaining the frequency signature of the resonances. Localized scrutiny of a specific scale may then be achieved using the STFT, while super resolution may be achieved using a model based analysis View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Synthesis of purely dielectric transient lenses

    Page(s): 203 - 212
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    It is shown that the generalized form of a TEM plane wave involving inhomogeneous constitutive parameters can be used for the formal fields for synthesizing lens designs based on differential-geometric scaling. This will allow one to have purely dielectric lenses (with free space permeability), and will provide an extra degree of freedom in lens design. It is also shown that guided TEM waves can be propagated in inhomogeneous isotropic media with permittivity proportional to Ψ-2, where Ψ is the cylindrical radius. Also, very general conductor cross sections can be specified, which allows for the construction of dispersionless bends in high-voltage transmission systems in which the pulse rise time is small compared to transit times across the transmission line (e.g. coax) cross section, a matter of importance for applications in high-power pulse generation and antenna design and for low-loss transmission lines View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time focusing of electromagnetic sounding in conductive media using similarities between wave and diffusion propagation

    Page(s): 449 - 456
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    By using similarities between EM sounding in dielectric and conductive media, it is shown that one can transform between solutions in one type of propagation to the other. The method is based on the similarities of the Laplace transform between the diffusive and the nondiffusive cases. In the diffusive case the equation involves the Laplace variable s in the first power while for the nondiffusive cases similar equations occur with s2. Three alternative implementations are developed and their use is demonstrated. The first implementation is based on substitution s2 for the Laplace transform variable s using forward and inverse numerical Laplace transform. The second implementation is based on expanding the diffusive time response on an exponential time base and replacing it with its image function in the wave case, namely a sinusoidal function. The third implementation is based on direct transformation in the time domain using exponential time interval sampling. The advantages of the techniques are their simple implementation. Other advantages and limitations of the method and each of the implementations are discussed. Application of common techniques used in processing of seismic radar for processing and EM sounding in conductive media are discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Propagation of ultrawideband pulsed radiation in conducting medium

    Page(s): 313 - 319
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    A new method of solving the problem concerning a plane electromagnetic pulse scattering at the boundary of a conducting half-space has been discussed. Permittivity and permeability of a half-space dispersive medium are assumed not to depend on frequency. Application of nonseparable solutions of the Klein-Gordon equation reduce the problem of determining a field in a conducting medium. It has been shown that if the field at the medium boundary is determined then it allows to effectively calculate the field in the medium using an orthonormalized function system formed from linearly independent solutions of the Klein-Gordon equation. The scattered field is presented by expansions on orthonormalized system of Laguerre functions View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Ultra-wideband analogue channels using solitons

    Page(s): 237 - 242
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    It is shown that the dynamics of N-solitons of the Korteweg-de Vries (KdV) equation can be reduced to the Toda lattice equations for the temporal positions of the solitons when the solitons are nearly identical and widely separated in time. Invariants of the KdV equation map to corresponding invariants of the Toda lattice, and the map exists in the limit N→∞. These invariants form analogue channels for the communication of data in which an exact memory of the initial conditions is preserved, even though the KdV wavetrain itself is evolving dynamically. It follows that there exist channels which are immune to the effects of the interpulse dynamics in the KdV wavetrain View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modification of the aperture synthesizing method for underground sounding data processing

    Page(s): 443 - 448
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    The creation of subsurface radar systems is a significant problem in modern radio physics and thus has been investigated by many authors. The ultrawideband (videopulse) scanning systems usually produce data which are hard to interpret. This leads to the necessity of developing efficient data processing algorithms. The synthetic aperture method (SAM) seems to be one of the most powerful techniques of data processing in this area. SAM is based upon the following two-stage procedure: 1) application of a compression filter to the signals reflected by the medium (echo-returns), the filter indicates the presence of the object reflected signal; and 2) spatial convolution of the obtained set of the echo-returns. Natural and numerical experiment results show that useful algorithms for subsurface data processing can be developed on the basis of the synthetic aperture algorithm. Nevertheless some modifications of this algorithm have to be carried out in order to achieve accessible results in real media data processing. In this paper the algorithms aimed at the correction of the inverse-matched filter and computation time reduction are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Antenna-source integrated ultra-wideband electromagnetic pulses radiating device

    Page(s): 145 - 148
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    In 1901 Marconi tested the propagation property of electromagnetic fields using the folded monopole antenna, which was 150 ft in height, 200 ft in width, and excited at the tip of the monopole by the shorting of a spark gap. In the study of ultra-wideband electromagnetic pulse technology, we noted that with some improvements, the prototype method Marconi used has significant advantages over the popular source-antenna-separated microwave launching system, especially for producing and launching Ultra-WideBand (UWB), high power level, and impulsive electromagnetic fields. As the power level increases and risetime decreases, the transmission line approximation turns out to be unsuitable for analyzing the field distribution of UWB systems with baluns and transmission lines, owing to the transit time dispersion, skin and dielectric losses, and electrical breakdown effects. Therefore, the introduction of baluns and transmission lines into high power level UWB systems will degrade the system performance, and make the theoretical analysis of the loss mechanism extremely difficult. By integrating the source and antenna directly, one can reduce the loss significantly and design a compact, simple, and robust device that can be used to produce and radiate UWB pulses simultaneously. This paper presents the design and experimental study of the so-called “source-antenna-integrated” device, including the theoretical analysis and numerical simulation of the conical antenna View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Aperture efficiencies of impulse radiating antennas

    Page(s): 91 - 108
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1652 KB)  

    A concept of aperture efficiency is introduced for the purpose of comparing and optimizing the performance of impulse radiating antennas (IRAs). The aperture efficiencies of popular lens and reflector IRAs are computed as the ratios of peak radiated power densities on boresight compared with that produced by an ideal IRA with an aperture of equal area and equal total input power. Loss of aperture efficiency occurs through two distinct mechanisms: from power that falls outside the aperture and is lost; and from nonuniform power and polarization distributions within the aperture. Both loss mechanisms are addressed, and means for increasing efficiencies are identified. Aperture efficiencies approaching 100% are feasible in TEM-horn arrays and similar structures View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Space-time Green function and short pulse propagation in different media

    Page(s): 301 - 311
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    The facilities of using the space-time Green function (GF) for the short pulse propagation analysis were discussed. The GF application reduces a boundary-value problem to an integral calculation, The usefulness of this way is determined by the facilities of an exact and simple enough GF construction and a convenient calculation of obtained integrals. An explicit form of GF can be expressed exactly through the known functions for conducting media, long line and cold plasma without collisions. In other cases it should be calculated approximately. In this work the use of the exact GF form was considered. The propagation of two forms of the pulse was observed. The integral presentation for the rectangular pulse was calculated numerically. The asymptotic expansion was obtained for the pulse where a smallness of the effective pulse time duration was used View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Universal sensor using electro-optic sensing principles

    Page(s): 49 - 56
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    Techniques like high power microwaves (HPM), pulse scattering, EMP, ESD and transient radar still lack reliable electric field monitors. One of the main obstacles to develop such field sensors are the enormous difficulties to miniaturize the sensor head providing simultaneously sufficient sensitivity, dynamic range and electrical isolation. This paper presents a recent sensor development of a universal photonic field probe for transient and continuous wave electric field measurements. The probe head incorporates three electrooptic Lithium Niobate (LiNbO3) modulators packaged in purely dielectric material. The modulators cover a frequency range from dc to 3.5 GHz, where in the range dc to 1 GHz an amplitude flatness of ±0.5 dB can be specified. The modulator input impedance has been optimized to provide maximum electric field sensitivity in conjunction with a broad band dipole antenna. The sensor system including an 240 mW low noise, single frequency laser and 18 GHz bandwidth GaInP photo detectors reaches a pulse sensitivity of 4.5 V/m. For narrow band measurements a sensitivity limit of about 100 μV/m/√Hz can be extrapolated. The 1 dB compression point has been set to 12 kV/m peak to peak and could be increased to about 50 kV/m loosing sensitivity correspondingly. The sensor operates passively and is inherently potential-free by means of optical fibers with a length of up to 2 km. The modulators have been hermetically sealed and allow measurements in liquids in a depth of up to 4 meters View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.