Papers by Arthur Yaghjian
IEEE Transactions on Antennas and Propagation, Dec 1, 2010
We study the effect of surrounding electrically small, top-loaded, electric-dipole antennas with ... more We study the effect of surrounding electrically small, top-loaded, electric-dipole antennas with a thin shell of high-permeability magnetic material. The magnetic polarization currents induced in the thin shell of magnetic material reduce the internal stored energy, resulting in a lower Q as compared to conventional designs. The simulated Q of thinmagnetic-shell cylindrical and spherical antennas are compared to recently derived lower bounds on Q. The high permeability shells reduce the Q of these antennas to values below the lower bounds for purely global electric current sources. In the case of the spherical electric-dipole antenna, a sufficiently large value of permeability enables the Q to be reduced to a value that is only 1.11 times the Chu lower bound.
IEEE Antennas and Wireless Propagation Letters, 2007
We examine the behavior of a matched electrically small antenna that exhibits two impedance reson... more We examine the behavior of a matched electrically small antenna that exhibits two impedance resonances within its defined voltage standing wave ratio (VSWR) bandwidth. The exact quality factor (Q), computed indirectly from the antenna's input reactance and far field, is compared to twice the inverse of the matched half-power VSWR bandwidth (Q BW) and to an approximate quality factor (Qz)
Radio Science, May 14, 2008
The theory, computer simulations, and experimental measurements are presented for electrically sm... more The theory, computer simulations, and experimental measurements are presented for electrically small two-element supergain arrays with near optimal endfire gains of 7 dB. We show how the difficulties of narrow tolerances, large mismatches, low radiation efficiencies, and reduced scattering of electrically small parasitic elements are overcome by using electrically small resonant antennas as the elements in both separately driven and singly driven (parasitic) two-element electrically small supergain endfire arrays. Although rapidly increasing narrow tolerances prevent the practical realization of the maximum theoretically possible endfire gain of electrically small arrays with many elements, the theory and preliminary numerical simulations indicate that near maximum supergains are also achievable in practice for electrically small arrays with three (and possibly more) resonant elements if the decreasing bandwidth with increasing number of elements can be tolerated.
The IMA volumes in mathematics and its applications, 1992
Final Report, 1979
A four phase evaluation of high resolution remote sensing techniques for application to problems ... more A four phase evaluation of high resolution remote sensing techniques for application to problems of determining slope stability is presented. The first two phases concentrated on documenting the subsurface features and associated characteristics which determine or influence slope stability. A variety of electromagnetic and acoustic remote sensing techniques which exhibited the greatest potential for detecting the subsurface features and characteristics
Abstract : This report addresses the problem of formulating planar near-field antenna measurement... more Abstract : This report addresses the problem of formulating planar near-field antenna measurements in the time domain, so that a single set of time-domain near-field measurements yields the far-field pattern in the time domain or over a wide range of frequencies. The time-domain planar near-field techniques are developed for both acoustic and electromagnetic fields and the space outside the region occupied by the antenna is assumed to be isotropic and homogeneous. Probe correction is ignored, that is, it is assumed that the probe is ideal so that the exact values of the field on the measurement plane are known. Two fundamentally different approaches are used in deriving time-domain formulas which give the fields in the half space z > z sub 0, in terms of their values on the plane z = z sub 0. In the first approach the time-domain formulas are obtained by inverse Fourier transforming the corresponding frequency-domain formulas. Since this approach requires extensive use of the frequency domain near-field formulas, we start by giving a rigorous derivation and review of the frequency-domain formulation that addresses a number of subtleties that have not been dealt with adequately in the literature. As part of this review, planar near-field formulas for the static electric and magnetic fields are derived for the first time. In the second approach the time-domain near-field formulas are derived directly in the time domain. The equivalence of the resulting time- domain formulas obtained by the two different approaches demonstrates the validity of the formulas and the utility of both approaches. Near-field measurements, Planar scanning, Time-domain.
Unclassified 2a. SECURITY CLASSIFICATION AUTHORITY 3-DISTRIBUTION/AVAILABILITY OF REPORT Approved... more Unclassified 2a. SECURITY CLASSIFICATION AUTHORITY 3-DISTRIBUTION/AVAILABILITY OF REPORT Approved for public release; distribution 2b. DECLASSIFICATION / DOWNGRADING SCHEDULE unlimited. 4. PERFORMING ORGANIZATION REPORT NUMBER(S) 5. MONITORING ORGANIZATION REPORT NUMBER(S) RADC-TR-88-119 6a. NAME OF PERFORMING ORGANIZATION 6b. OFFICE SYMBOL 7a. NAME OF MONITORING ORGANIZATION
Over a period of about twenty years, Maxwell's determination and unification of the equations of ... more Over a period of about twenty years, Maxwell's determination and unification of the equations of electricity and magnetism evolved from his first paper on the subject in 1855-56, "On Faraday's Lines of Force," to the publication of his Treatise on Electricity and Magnetism in 1873. Notwithstanding the many historical accounts and textbooks devoted to Maxwell's work, I have not been able to find a reasonably concise, yet definitive summary of the fundamentals of exactly what Maxwell did in his Treatise and how he did it. This paper represents my own attempt to provide such a summary.
This report has been reviewed by the RADC Public Affairs Office (PA) and is releasable to the Nat... more This report has been reviewed by the RADC Public Affairs Office (PA) and is releasable to the National Technical Information Service (NTIS). At NTIS it will be releasable to the general public, including foreign nations. RADC-TR-87-213 has been reviewed and is approved for publication.
Progress in Electromagnetics Research B, 2015
Since both metamaterials composed of artificial molecules (inclusions in a host material) and nat... more Since both metamaterials composed of artificial molecules (inclusions in a host material) and natural molecular materials at optical and greater frequencies can exhibit significant electric quadrupolarization as well as electric and magnetic dipolarization, we determine the passive, causal electric quadrupolarizability for a spherically symmetric molecule, namely a dielectric sphere subject to source-driven applied fields. For source-driven excitations, it is found that two electric quadrupolarizability constants are generally required to characterize the electric quadrupolar response of the sphere, with one of the constants multiplying the divergence of the applied electric field. For source-free fields, such as the fields of the eigenmodes of an electric quadrupolar array, the local electric field illuminating each inclusion is solenoidal, the constitutive relation is characterized by just one quadrupolarizability constant, and the electric quadrupolarization becomes traceless. It is also found that the electric quadrupolarization becomes very large and effectively traceless near the resonant frequencies of electrically small plasmonic spheres with negative permittivity and for somewhat larger spheres with positive permittivity.
Electromagnetic waves, 2014
Over a period of about twenty years, Maxwell's determination and unification of the equations of ... more Over a period of about twenty years, Maxwell's determination and unification of the equations of electricity and magnetism evolved from his first paper on the subject in 1855-56, "On Faraday's Lines of Force," to the publication of his Treatise on Electricity and Magnetism in 1873. Notwithstanding the many historical accounts and textbooks devoted to Maxwell's work, I have not been able to find a reasonably concise, yet definitive summary of the fundamentals of exactly what Maxwell did in his Treatise and how he did it. This paper represents my own attempt to provide such a summary.
Physical Review E, Oct 10, 2008
The restrictions of analyticity, relativistic (Born) rigidity, and negligible O(a) terms involved... more The restrictions of analyticity, relativistic (Born) rigidity, and negligible O(a) terms involved in the evaluation of the self electromagnetic force on an extended charged sphere of radius a are explicitly revealed and taken into account in order to obtain a classical equation of motion of the extended charge that is both causal and conserves momentum-energy. Because the power-series expansion used in the evaluation of the self-force becomes invalid during transition time intervals immediately following the application and termination of an otherwise analytic externally applied force, a transition force must be included during each of these two transition time intervals to remove the noncausal pre-acceleration and pre-deceleration from the solution to the equation of motion without the transition forces. Although the exact time dependence of each transition force is not known, the effect of each transition force on the solution to the equation of motion can be determined to within a single unknown constant, the change in velocity of the charge across the transition interval. For the extended charged sphere, the changes in velocity across the transition intervals can be chosen to maintain conservation of momentum-energy in the causal solutions to the equation of motion within the restrictions of relativistic rigidity and negligible O(a) terms under which the equation of motion is derived. However, regardless of the values chosen for the changes in the velocity across the transition intervals, renormalization of the electrostatic mass to a finite value as the radius of the charge approaches zero introduces a violation of momentum-energy conservation into the causal solutions to the equation of motion of the point charge if the magnitude of the external force becomes too large. That is, the causal classical equation of motion of a point charge with renormalized mass experiences a high acceleration catastrophe.
IEEE Microwave and Wireless Components Letters, Jul 1, 2007
ABSTRACT
Journal of the Acoustical Society of America, Sep 1, 1991
Simple spherical-wave expansions of the continuous-wave fields of a circular piston radiator in a... more Simple spherical-wave expansions of the continuous-wave fields of a circular piston radiator in a rigid baffle are derived. These expansions are valid throughout the illuminated half-space and are useful for efficient numerical computation in the near-field region. Multipole coefficients are given by closed-form expressions which can be evaluated recursively.
IEEE Transactions on Antennas and Propagation, May 1, 1997
In Section II of the above paper 1 we stated that (1a) and (1b) give the incremental length diffr... more In Section II of the above paper 1 we stated that (1a) and (1b) give the incremental length diffraction coefficients (ILDC's) for the nonuniform current of a half-plane illuminated by a TM (E polarized) and TE (H polarized) plane wave, respectively. In fact, (1a) and (1b) give the ILDC's for the total current of a half-plane, not the Manuscript
IEEE Transactions on Antennas and Propagation, 2001
Shadow boundary incremental length diffraction coefficients (SBILDCs) are high-frequency fields d... more Shadow boundary incremental length diffraction coefficients (SBILDCs) are high-frequency fields designed to correct the physical optics (PO) field of a three-dimensional (3-D) perfectly electrically conducting scatterer. The SBILDCs are integrated along the shadow boundary of the 3-D object to approximate the field radiated by the nonuniform shadow boundary current (the difference between the exact and PO currents near the shadow boundary). This integral is added to the PO field to give an approximation to the exact scattered field that takes into account both PO and nonuniform shadow boundary currents on the scatterer. Like other incremental length diffraction coefficients, any SBILDC is based on the use of a 2-D canonical scatterer to locally approximate the surface of the 3-D scatterer to which it is applied. Circular cylinder SBILDCs are, to date, the only SBILDCs that have been obtained in closed form. In this paper, these closed-form expressions are validated by applying them for the first time to a 3-D scatterer with varying radius of curvature-the prolate spheroid. The results obtained clearly demonstrate that for bistatic scattering the combined PO-SBILDC approximation is considerably more accurate than the PO field approximation alone.
Radio Science, Nov 1, 1996
Shadow boundary incremental length diffraction coefficients (SBILDCs) are high-frequency fields d... more Shadow boundary incremental length diffraction coefficients (SBILDCs) are high-frequency fields designed to correct the physical optics (PO) field of a three-dimensional (3-D) perfectly electrically conducting scatterer. The SBILDCs are integrated along the shadow boundary of the 3-D object to approximate the field radiated by the nonuniform shadow boundary current (the difference between the exact and PO currents near the shadow boundary). This integral is added to the PO field to give an approximation to the exact scattered field that takes into account both PO and nonuniform shadow boundary currents on the scatterer. Like other incremental length diffraction coefficients, any SBILDC is based on the use of a 2-D canonical scatterer to locally approximate the surface of the 3-D scatterer to which it is applied. Circular cylinder SBILDCs are, to date, the only SBILDCs that have been obtained in closed form. In this paper, these closed-form expressions are validated by applying them for the first time to a 3-D scatterer with varying radius of curvature-the prolate spheroid. The results obtained clearly demonstrate that for bistatic scattering the combined PO-SBILDC approximation is considerably more accurate than the PO field approximation alone.
American Journal of Physics, Sep 1, 1985
Maxwellian and cavity electromagnetic fields are derived within a continuous source distribution ... more Maxwellian and cavity electromagnetic fields are derived within a continuous source distribution of volume current or electric and magnetic polarization densities by direct, rigorous differentiation of the vector potential. The derivation, which uses only operations of vector calculus, reveals naturally the contributions from interior and exterior source regions. Results are obtained for static and arbitrarily time-varying fields as well as for time-harmonic fields.
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Papers by Arthur Yaghjian