By Topic

Antennas and Propagation, IEEE Transactions on

Issue 9 • Date Sept. 1991

Filter Results

Displaying Results 1 - 25 of 26
  • Diffraction by an arbitrary-angled dielectric wedge. II. Correction to physical optics solution

    Publication Year: 1991 , Page(s): 1282 - 1292
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (653 KB)  

    For pt.I see ibid., vol.39, no.9, p.1272-81 (1991). The error of the physical optics solution for the E-polarized plane wave incidence in connection with diffraction by an arbitrary-angled dielectric wedge is corrected by calculating the nonuniform current distributed along the dielectric interfaces. Two kinds of series expansions to the nonuniform current are employed. One is an asymptotic expansion as the multipole line source located at the edge of the dielectric wedge, since the correction field seems to be a cylindrical wave emanating from the edge in the far-field region. The other is arbitrary electric and magnetic surface currents expanded by infinite series of the Bessel functions, i.e. the Neumann expansion, of which fractional order is chosen to satisfy the edge condition near the edge of the dielectric wedge in the static limit. Both of the two different expansion coefficients for a wedge angle of 45 degrees , relative dielectric constants 2, 10, and 100, and the E-polarized incident angle of 150 degrees are evaluated by solving the dual series equation numerically after finite truncation.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comments on "An improved formula for the resonant frequency of the triangular microstrip path antenna" [with reply]

    Publication Year: 1991 , Page(s): 1443 - 1445
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (129 KB)  

    The commenters claim to have found several errors in the paper by Garg and Long (see ibid., vol.36, no.4, p.570, Apr. 1988). An author's reply is presented.<> View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electric field singularities at sharp edges of planar conductors

    Publication Year: 1991 , Page(s): 1312 - 1320
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    The electric field behavior around printed conductors with a polygonal contour, as used in antennas and microwave circuit components, is investigated. The diffraction problem posed by these geometries involves edge and vertex conditions as well as boundary conditions. These can collectively be described by means of a simple singularity function that gives the distribution of zeros of the electric field on the flat conductor surfaces and of its singularities along the conductor edges. The analysis is based on solving the vector Helmholtz equation for the plane-sector perfect conductor in a conical coordinate system, and the static case is derived from a limit process. The values of the singularity function for the electric field components are explicitly reported for the more commonly encountered 90° and 270° sectors and for 90° bitriangular antennas. Systematic extension to sectors of arbitrary aperture, to composite configurations, and to their polygonal combinations is also indicated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modeling of thin dielectric structures using the finite-difference time-domain technique

    Publication Year: 1991 , Page(s): 1338 - 1344
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    The finite-difference time-domain (FDTD) technique is applied to scattering problems involving thin dielectric sheets, conductor-backed dielectric sheets, and conductor-backed dielectric sheets containing cracks in the dielectric material. A smart cell technique is developed that enables these geometries to be modeled with a spatial grid that is much larger than the dielectric slab and crack widths. This technique is computationally more efficient than the `brute force' (or ordinary) FDTD approach, which must use cells small enough to resolve the dielectric sheets. Numerical results are presented which show that this technique yields accurate scattering results at a large savings in computational resources View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High frequency scattering from trihedral corner reflectors and other benchmark targets: SBR versus experiment

    Publication Year: 1991 , Page(s): 1345 - 1351
    Cited by:  Papers (34)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    A general method for calculating the radar cross section (RCS) from a three-dimensional target is described. The target is first constructed by using a solid-geometry-modeling computer-aided design (CAD) package. Following the shooting and bouncing ray (SBR) method, a very dense grid of rays is launched from the incident direction toward the target. Each ray is traced according to the geometrical optics theory including the effect of ray tube divergence, polarization, and material reflection coefficient. At the point where the ray exits the target, a physical optics-type integration is performed to obtain the scattered far fields. This method is tested using several simple examples involving interaction among plates, cylinders, and spheres. The theoretical results are generally in good agreement with measured data View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An improvement of parasitic dipole array using suppressor elements

    Publication Year: 1991 , Page(s): 1434 - 1436
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    A novel configuration of parasitic arrays is introduced. The characteristics of the array in both forward and backward radiation are improved by using a new element, the suppressor. The suppressor elements are aligned parallel to a radiating dipole or to a conventional endfire array such as a Yagi-Uda array. Radiation in the unwanted direction is reduced by the suppressors, and the forward gain is effectively increased. Design of the optimum antenna parameters was achieved using the moment method, and results were compared to measured values, with good agreement obtained. New arrays were compared to well-designed Yagi-Uda arrays. A new array which is aligned with two broadside suppressors and with three endfire elements had an improved forward gain of 1.5 dB and a reduced backward gain of -4 dB compared to a conventional, well designed Yagi-Uda array with five endfire elements View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of microstrip antennas on circular-cylindrical substrates with a dielectric overlay

    Publication Year: 1991 , Page(s): 1398 - 1404
    Cited by:  Papers (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    The use of dyadic Green's functions and the moment method is explored for the solution of microstrip antenna problems on circular cylindrical substrates. The dyadic Green's functions of the electric type are obtained for a medium consisting of three cylindrical dielectric layers concentric with a perfectly conducting cylinder, and integral equations are developed for the evaluation of the electromagnetic fields. The effect of a dielectric overlay on the resonant frequency of a cylindrical-rectangular microstrip antenna is analyzed. The patch is directly fed by means of a microstripline printed along the cylinder axial direction. The results show that the effect of the dielectric overlay is substantial when its relative permittivity and thickness are increased, such that this effect has to be very carefully considered in the design of microstrip antennas View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new methodology for reconstructing aperture fields from spherical surface data, with application to array antenna diagnostics

    Publication Year: 1991 , Page(s): 1436 - 1441
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    A novel algorithm for deriving diagnostics from spherical surface measurement data is described. In keeping with a `black-box' testing rationale, no initial assumptions are made as to the properties of the antenna under test. Nevertheless, high-resolution reconstructions may be generated. In the case of planar array diagnosis, single element excitation faults may be quantified to an accuracy of 0.25 dB and 2° View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Radiation of millimeter waves from NRD leaky wave antennas with tapered transition and tuning aperture

    Publication Year: 1991 , Page(s): 1366 - 1371
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    The radiation of millimeter waves from the nonradiative dielectric (NRD) leaky wave antennas with the tapered transition and the tuning aperture is investigated. An accurate theory for the leakage constant and the phase constant of the antennas is presented, which is based on the generalized scattering parameters considering the higher-order mode interactions at the discontinuities. The associated transverse equivalent network involves the characterization of the mode couplings at two air-to-dielectric interfaces, the coupled mode analysis of the tapered transition, and the calculation of the radiation fields at the tuning aperture via the extended spectral domain approach. The interesting behavior of the present modified configuration of NRD leaky wave antennas is illustrated by typical examples. The validity of the theory is confirmed by the comparison of the theoretical results with experimental data for the limiting cases View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of an arcjet plume on satellite reflector performance

    Publication Year: 1991 , Page(s): 1412 - 1420
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (692 KB)  

    The effect of an arcjet plume on the performance of satellite reflector antennas is studied. The arcjet plume is modeled as a weakly ionized plasma. The spatial permittivity distribution of the plume is approximated using the measured electron density profile and a cold plasma model. Geometrical optics is applied to determine the ray paths as well as the transmitted fields through the inhomogeneous plume. The ray optics results are compared against several exact solutions for scattering from inhomogeneous dielectrics, and good agreement is observed for sufficiently large scatterer size. The far-field antenna patterns of the reflector in the presence of the plume are calculated from the transmitted ray fields using a ray-tube integration scheme. For arcjet prototypes in the 1-kW class, the plume effect on the antenna performance is small. As the electron density increases, the main beam and sidelobe level gradually degrade. The main beam also tends to squint away from the plume region View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On estimating the number of sources with a frequency-hopped signaling sensor array

    Publication Year: 1991 , Page(s): 1384 - 1390
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    Frequency-hopped signaling is proposed to improve the estimation of the number of diversely moving sources/targets by a sensor array. Information-theoretic criteria are employed in the analysis, and simulation results are presented. It is shown that, by appropriately designing the pulse period and the subpulse frequencies, the system performance using frequency-hopped signaling is much better than that of the conventional array with a monotone frequency when the element signal-to-noise ratio is above a certain threshold. For a given system bandwidth, the noise performance saturates when the number of frequency hops becomes large View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Diffraction by an arbitrary-angled dielectric wedge. I. Physical optics approximation

    Publication Year: 1991 , Page(s): 1272 - 1281
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    A complete form is presented of the physical optics solution to diffraction by an arbitrary dielectric wedge angle with any relative dielectric constant in cases of both E- and H-polarized plane waves incident on one side of two dielectric interfaces. The solution, which is obtained by performing the physical optics (PO) approximation to the dual integral equation formulated in the spatial frequency domain, is constructed by the geometrical optics terms, including multiple reflection inside the wedge and the edge diffracted field. The diffraction coefficients of the edge diffracted field are represented in a simple form as two finite series of cotangent functions weighted by the Fresnel reflection coefficients. Far-field patterns of the PO solutions for a wedge angle of 45°, relative dielectric constants 2, 10, and 100, and an E-polarized incident angle of 150° are plotted in figures, revealing abrupt discontinuities at dielectric interfaces View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Linear array characteristics with one-dimensional reactive-region near-field scanning: simulations and measurements

    Publication Year: 1991 , Page(s): 1305 - 1311
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    A model for simulating the performance of a phased-array antenna with one-dimensional near-field scanning is addressed. Measurements and simulations in the reactive near-field region for a linear array with monopole elements are described. The array and near-field probe characteristics are simulated by using the method of moments. Measurements and simulations of the array near-zone received voltage, plane-wave spectrum, and far-field data, using centerline scanning at less than one wavelength distance from the antenna, are shown to be in good agreement. The presence of evanescent grating lobes in the plane-wave spectrum is observed. It is shown that a V-dipole theoretical probe antenna can accurately model a practical near-field measurement probe View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of electromagnetic scattering from linear periodic arrays of perfectly conducting bodies using a cylindrical-current model

    Publication Year: 1991 , Page(s): 1332 - 1337
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    A novel solution is presented for the problem of three-dimensional scattering of a time-harmonic plane wave from a infinite periodic linear array of finite-size perfectly conducting bodies. A set of fictitious sources comprising periodic and properly modulated cylindrical electric current sheets of cross polarization is used to simulate the scattered field. The complex amplitudes of these fictitious sources are adjusted to render the tangential component of the electric field zero at a selected set of points on the surface of one of the scatterers. The suggested solution procedure is simple to implement and is applicable to linear periodic arrays composed of disjoint bodies of smooth, but otherwise arbitrary, shape. The accuracy of the method is demonstrated. It is shown that in the limiting case of widely spaced spherical scatterers the numerical solution agrees well with an approximate analytic solution View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Radiation characteristics of a dielectric disk-loaded circular cylindrical waveguide

    Publication Year: 1991 , Page(s): 1430 - 1434
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    The radiation pattern of a circular cylindrical waveguide that is loaded inside with periodically spaced dielectric disks is derived by considering the region between two disks as a medium with anisotropic permittivity and using Schelkunoff's equivalence principle. The far-field electric field components and their relationship to cross-polarization ratio are determined. The variation of the latter quantity with the size, spacing, and dielectric constant of the dielectric disks is studied View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Polarimetric scattering from natural surfaces at 225 GHz

    Publication Year: 1991 , Page(s): 1405 - 1411
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    Polarimetric radar measurement at 225 GHz which demonstrate that the normalized Mueller matrix may be approximated in terms of a single parameter are presented. The depolarization ratio, defined as the ratio of cross-polarized to co-polarized normalized radar cross section, is shown to accurately predict backscatter from vegetation (trees and grass), as well as scattering from terrain at low incidence angles (snowcover and sand). The depolarization ratio also predicts the standard deviation of the scattered field ellipse parameters View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Angle and polarization estimation using ESPRIT with a polarization sensitive array

    Publication Year: 1991 , Page(s): 1376 - 1383
    Cited by:  Papers (65)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    It is shown how estimation of signal parameters via rotational invariance techniques (ESPRIT) may be used to estimate both the arrival directions and the polarizations of incoming plane waves with a uniform linear array of crossed dipoles. The ESPRIT algorithm exploits the invariance properties of such an array so that both angle and polarization estimates may be computed. Some typical examples showing the use of this method are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The Fourier transform of linearly varying functions with polygonal support

    Publication Year: 1991 , Page(s): 1441 - 1443
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    New formulas for the two-dimensional Fourier transform of functions with polygonal support and linear amplitude variation are derived from the corresponding formula for a constant function. These expressions, valid for all nonzero values of the transform variable k, are superior to those previously reported, which fail when k is perpendicular or parallel to any edge of the polygon. These transforms have applications in diffraction theory and computational electromagnetics View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wave propagation through curved shells and the validity of the plane-slab approximation

    Publication Year: 1991 , Page(s): 1265 - 1271
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    A variety of results is presented for the transmission of microwaves through curved shells. Cylindrical shells with line sources and spherical shells with dipole sources, located in the shell cavity, are considered, and ray theory is applied in systematic computation following G.H. Deschamps' procedure (1972). The ray tracing procedure implemented in the program includes the contribution of multiple reflections between the shell dielectric and free-space medium interface. These results are compared with the local plane-slab approximation described by G. Tricoles (1964). Errors <1% in magnitude are found for radii of curvature >10 λ0, and thickness <1% λ0. For the extreme case of shells with radii <5 λ0 and thickness greater than 1 λ0, the plane-slab approximation appears to have significant error. Typically, for a shell of radius 5 λ0 and thickness of 1 λ0, the error in the normalized far field is less than 4%. The procedure of P.D. Einziger and L.B. Felsen (1983) is extended to provide a basis for the plane-slab approximation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Low-sidelobe reflector synthesis and design using resistive surfaces

    Publication Year: 1991 , Page(s): 1372 - 1375
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A procedure is presented for determining the resistivity of a paraboloid's reflecting surface to obtain a desired sidelobe level. The only requirement is that the normalized aperture distribution due to the feed be greater than the corresponding normalized low sidelobe distribution at every point on the reflector (i.e. the reflection coefficient of the surface ⩽1). In the synthesis procedure, blockage is ignored and an ideal feed is assumed. In spite of this, computation of the secondary radiation patterns of a resistively corrected antenna including the feed using the method of moments shows that a -40-dB sidelobe level is achievable. In principal, there is no limit to the sidelobe reduction for the field scattered from the reflector. In practice, blockage, feed illumination errors, errors in the surface resistivity, and the feed backlobe will limit the sidelobe level View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Full wave analysis for rough surface diffuse, incoherent radar cross sections with height-slope correlations included

    Publication Year: 1991 , Page(s): 1293 - 1304
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    The bistatic scattering cross sections are derived for rough one-dimensional perfectly conducting surfaces using the full wave approach. The surfaces are characterized by four-dimensional Gaussian joint probability density functions for heights and slopes. Thus, correlations between the rough surface heights and slopes are accounted for in the analysis. Convergence of the formal series solution is considered. Self-shadowing effects are included. The full-wave solutions are compared with the small perturbation solutions, which are polarization dependent, and the specular point (physical optics) solutions, which are independent of polarization. Both the physical optics and the small perturbation solutions can be obtained from the full-wave solution View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • H-field and J-current singularities at sharp edges in printed circuits

    Publication Year: 1991 , Page(s): 1321 - 1331
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    The magnetic field and related current density behavior on the surface of printed conductors with a polygonal contour used in MIC (microwave integrated circuit) components and antennas are investigated. From the rigorous E solution for the plane sector perfect conductor, the H singular solution is determined. The authors formulate a convenient singularity function that just represents the boundary conditions and the singularity distributed along the conductor edge. The singularity function is explicitly reported for the commonly encountered 90° and 270° plane sectors and 90° bitriangular antenna, and its systematic generalization is indicated for sectors of arbitrary aperture and composite configurations and polygonal path View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A new class of resonant antennas

    Publication Year: 1991 , Page(s): 1428 - 1430
    Cited by:  Papers (30)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    A new class of wire antennas called meander antennas is introduced as possible elements for size reduction. Efficiency is affected only by the ohmic losses in the wire, and cross polarization is negligible. An increase in the number of meander sections introduces less size reduction in return for an improved bandwidth. These antennas can be used to reduce the size of existing wire antennas such as Yagi-Uda antennas and log-periodic dipole arrays. A size reduction in the resonant length typically from 25-40% is obtained. More size reduction is obtained by decreasing the radius of the wire or increasing the separation of the folded arms View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Use of antenna nulling with frequency-hopping against the follower jammer

    Publication Year: 1991 , Page(s): 1391 - 1397
    Cited by:  Papers (12)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB)  

    Antenna nulling is an effective ECCM (electronic counter countermeasures) asset that can be put in use with other ECCM techniques to obtain additional processing gain. Two antenna nulling schemes that can be used with frequency hopping to reduce the follower jammer threat are described. One of the schemes is only effective with uncorrelated signals. The second scheme is designed for coping with correlated jamming. Both schemes capitalize on the arrival time differences of the desired signal and the interference to isolate the interference for cancellation. The fast converging sample matrix inversion algorithm is considered in both schemes for improved effectiveness. The performance of the antenna nulling schemes, described in terms of the array output-signal-to-interference and noise ratio (OSINR), is evaluated by computer simulation. The OSINR of the array at a single frequency in the hop-set is presented for a range of desired signal-to-noise and jammer-to-noise ratios. The processing gain offered by the antenna nulling system was found to increase with increasing desired signal-to-noise ratio View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the reflectivity of complex mesh surfaces [spacecraft reflector antennas]

    Publication Year: 1991 , Page(s): 1352 - 1365
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (884 KB)  

    Poorer than expected surface reflectivity was observed in an early Tracking and Data Relay Satellite System antenna utilizing a tricot mesh weave. This poor reflectivity was determined to be caused by inadequate electrical contact at wire crossover points. A proper mathematical and numerical approach to assess the impact of wire junctions on reflectivity performance is developed. A mathematical method is presented for computing the surface reflectivity of complex mesh configurations like those on unfurlable-type spacecraft antennas. The method is based on the Floquet mode expansion to establish an integral equation for mesh wire currents. The equation is solved using the method of moments with triangular basis functions. It is observed that it is necessary to give special attention to the junction treatment among different branches of the mesh configurations. A vector junction current approach that resulted in satisfactory solutions for the current is described. The results of numerical simulations are compared against measured data and excellent agreement is observed View full abstract»

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

Aims & Scope

IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief                                                 Kwok W. Leung