By Topic

Antennas and Propagation, IEEE Transactions on

Issue 10 • Date Oct 1993

Filter Results

Displaying Results 1 - 17 of 17
  • Electromagnetic wave propagation in multilayer dielectric periodic structures

    Page(s): 1432 - 1438
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    The propagation characteristics in multilayer dielectric periodic structures, that extends a previous analysis by introducing additional dielectric layers, is presented. It is applied to propagating electromagnetic modes along the longitudinal and transverse directions of the structure's periodicity. The use of Floquet's theorem reduces the analysis to a single cell of the propagating fields for both, TE and TM polarizations. Results showing the effect of varying the layers thickness and electric permittivity on the propagation constant and on the field distributions within each cell are presented as well as the band structure associated with the periodic structure View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of pyramidal horn antennas using moment methods

    Page(s): 1379 - 1389
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1032 KB)  

    A hybrid numerical technique is developed for electrically large pyramidal horn antennas radiating in free space. A stepped-waveguide method is used to analyze the interior surfaces of the horn transition. The electric field integral equation (EFIE) is employed on the outer surfaces of the pyramidal horn including the radiating aperture. Meanwhile, the magnetic field integral equation (MFIE) is used on the aperture to relate the aperture fields and those in the horn transition The resultant hybrid field integral equation (HFIE) is solved numerically by the method of moments. This formulation is both accurate and numerically stable so that high-gain microwave pyramidal horns can be analyzed rigorously. Far-field radiation patterns, both computed and measured, are presented for three electrically-large X-band horn antennas. The comparisons demonstrate that this method is accurate enough to predict the fine pattern structure at wide angles and in the back region. Computed far-field patterns and aperture field distributions of two smaller X-band horns are also presented along with a discussion on the validity of the approximate aperture field distributions routinely used in the analysis and design of pyramidal horns View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time-domain study of half-space transmission problem with vertical and horizontal dipoles

    Page(s): 1399 - 1407
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    The paper deals with the transient fields transmitted through the interface between the air and ground. Excitation for the electromagnetic fields is produced by a vertically or horizontally oriented impulsive dipole, which may be electric or magnetic. However, only electric sources are discussed, because the analog results for magnetic sources are obtained easily through the duality transform. The ground medium has arbitrary permittivity and permeability, but it is restricted to lossless, i.e. the conductivity is assumed to be zero. In this study simple integral expressions are derived for the time-dependent Hertz vector in the ground from which the propagating transient fields can be obtained through differentiation. In certain specific cases some components of electric or magnetic field have a closed-form solution in terms of elementary functions. All the nontrivial solutions of this type in the ground medium are given View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Propagation of EM pulses excited by an electric dipole in a conducting medium

    Page(s): 1414 - 1421
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    Exact solutions are given for the transient electromagnetic (EM) fields excited by an electric dipole antenna with an impulsive current in a conducting medium. There exists an optimum waveform for the antenna current which can generate an EM pulse with a maximum intensity at a particular distance from the antenna. It is found that the EM fields of an EM pulse excited by an antenna in a conducting medium can be divided into two parts. The first part is an impulse wave which propagates with the speed of light (1/√(με)) and decays exponentially. The second part builds up gradually and propagates slowly, and more importantly this part attenuates as an inverse power of distance which is a much slower rate than an exponential decay View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Radio propagation characteristics for line-of-sight microcellular and personal communications

    Page(s): 1439 - 1447
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    To acquire a knowledge of radio propagation characteristics in the microcellular environments for personal communications services (PCS), a comprehensive measurement program was conducted by Telesis Technologies Laboratory (TTL) in the San Francisco Bay area using three base station antenna heights of 3.2 m, 8.7 m, and 13.4 m and two frequencies at 900 MHz and 1900 MHz. Five test settings were chosen in urban, suburban, and rural areas in order to study propagation in a variety of environments. This paper reports the LOS measurements in different environments, all of which show variations of signal strength with distance that have distinct near and far regions separated by a break point. It was also found that the location of the break point for different frequencies and antenna heights can be calculated based on first Fresnel zone clearance. The regression analysis reveals a slope that is less than two before the break point, while it is greater than two after the break point. This break distance can be used to define the size of microcell and to design for fast hand-off. Beyond the first Fresnel zone break distance the base station antenna height gain was observed to approximately follow the square power law of antenna height View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Time-domain analysis of propagation in inhomogeneous anisotropic lossy slabs

    Page(s): 1456 - 1459
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    An equivalent-transmission-line-circuit (ETLC) model is developed to discuss the transient propagation problem of a plane wave in inhomogeneous, anisotropic, and transversely lossy slabs. This model is based on the analogy between the field equations and the coupled transmission line equations. By establishing the analogy, suitable lumped-circuit models are proposed to treat the equivalent transmission lines, which may then be solved by the circuit simulation program. In this study, the accuracy and convergence of the lumped-circuit models are examined. The ETLC model is then applied to discuss the propagation problem in anisotropic graphite/epoxy laminates with numerical results presented to show the transient responses due to the electromagnetic pulse and Gaussian pulse View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Truncation in millimeter and submillimeter-wave optical systems

    Page(s): 1408 - 1413
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    The authors present a technique for determining the power that is lost when the field in a beam waveguide is truncated by an axially-symmetric stop. The technique is based on the principles of multimode Gaussian optics. Although the underlying theory is applicable to any long-focal-length optical system, they concentrate on beam waveguides that are fed by diagonal horns, corrugated horns, smooth-walled conical horns, and uniformly-illuminated apertures. The results are summarized in a series of plots which show truncation loss as a function of normalised aperture size and phase slippage. These plots can be used together with single-mode design techniques to minimize the size of millimeter and submillimeter-wave optical systems View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The development of a model to estimate the bistatic transmission loss associated with intersystem interference

    Page(s): 1422 - 1431
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    This paper presents a new method for evaluating transmission loss, which is a key factor used in determining the impact of interference between terrestrial radio relay systems and Earth-satellite systems operating at the same frequency. The current model used by the CCIR was developed in the early 1970's when system packing density was low and large earth station antennas allowed the consideration of narrow beam approximations, resulting in a small common volume of intersection of the two beams. The recent increase in microwave communications traffic and improvements in technology have meant that smaller earth station antennas, including very small aperture terminals (VSATs), can be employed and hence the model requires revision. Results from the new model proposed are compared with two experimental geometries and good agreement is found View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Extended E-pulse technique for discrimination of conducting spheres

    Page(s): 1460 - 1462
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    The study presented is on the influence of forced-E-pulse duration in the discrimination capacity of the E-pulse technique, applied to spherical targets. This analysis allows three ranges of E-pulse durations to be considered and an optimum duration of the forced E-pulse to be obtained. The results obtained allow the discrimination technique to be extended in order to determine if the radius of an “unknown” sphere is longer or shorter than the radius of the “expected” one View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Theory and experiment of a coaxial probe fed hemispherical dielectric resonator antenna

    Page(s): 1390 - 1398
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    A hemispherical dielectric resonator antenna fed by a coaxial probe is studied both theoretically and experimentally. The Green's function for the evaluation of the input impedance is derived rigorously and expressed in a form convenient for numerical computations. The method of moments is used to obtain the probe current from which the input impedance of the DR antenna is calculated. Both delta gap and magnetic frill source models are considered. Moreover, the results using a reduced kernel as well as the exact kernel are presented. Both entire basis (EB) and piecewise sinusoidal (PWS) expansion modes are used and the results are compared. The effects of the probe length, feed position, and dielectric constant on the input impedance are discussed. Finally, the theoretical radiation patterns for the first three resonant modes (TE111, TM101, and TE221) of the DR antenna are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the numerical integration of the linear shape functions times the 3-D Green's function or its gradient on a plane triangle

    Page(s): 1448 - 1455
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    Formulas for the static and dynamic potentials due to linearly varying source distributions defined on a planar triangle are presented. The general linear variation of the source is represented in terms of three linear basis functions, each one associated with a different vertex of the triangular domain. The singular kernels considered are given by the 3-D Green's function and its gradient, both for the static and dynamic case. In the static case the evaluation of potentials is performed analytically and compact form results are given. In the dynamic case the results are given in a form suited for numerical integration View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis and design of multilayer printed antennas: a modular approach

    Page(s): 1371 - 1378
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    The problem of modular design of multilayer printed arrays is addressed. The use of slot as a means of power transfer between layers makes the use of multilayer feeding networks attractive. Four different transitions are analyzed using the moment method in the spectral domain. A typical equivalent circuit valid for all these transitions is used, and the comparison between the theoretical results and measurements is presented. Finally, the models developed for the individual transitions are used in the design of three multilayer antennas. In most of the cases, encouraging results are obtained in one design iteration View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Long-time behavior and energy growth for electromagnetic waves reflected by a moving boundary

    Page(s): 1365 - 1370
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    The author studies the phenomenon of a wave reflected back and forth between two parallel, perfectly conducting plates, one of which is oscillating normally to itself. By making a careful analysis of the reflected space-time characteristics he establishes a representation formula for the solutions of Maxwell's equations in terms of the initial data. This representation formula together with properties of iterated maps of an interval yield a precise asymptotic description as t→∞ of the solutions. The main result is that if there is a finite number of reflected characteristics which are periodic, then the energy of all solutions grows without bound as t→∞, irrespective of the initial data View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Standard probes for electromagnetic field measurements

    Page(s): 1349 - 1364
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1152 KB)  

    Discusses various standard antennas for measuring radio-frequency electric and magnetic fields. A theoretical analysis of each antenna's receiving characteristics is summarized and referenced. The standard probes described are an electrically short dipole, a resistively-loaded dipole, a half-wave dipole, an electrically small loop, and a resistively-loaded loop. A single-turn loop designed for simultaneous measurement of the electric and magnetic components of near-fields and other complex electromagnetic environments is also described. Each type of antenna demonstrates a different compromise between broadband frequency response and sensitivity View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A series solutions for TM-mode radiation from a flanged parallel-plate waveguide

    Page(s): 1469 - 1471
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (168 KB)  

    TM-mode radiation from a flanged parallel-plate waveguide is reexamined. The Fourier transform is used to represent the radiation field and the reflection coefficient in simple series forms. Computations are performed to illustrate the behaviors of the angular radiation pattern and the reflection coefficient. The series solution is fast convergent so that it is very efficient for numerical computation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis and development of a signal injection technique using transmission lines embedded at phased array aperture

    Page(s): 1464 - 1469
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    In a performance monitoring/fault isolation and correction (PM/FIC) system of a phased array antenna, a built-in transmission line embedded in the array aperture is used for signal injection to check the signal flow. The authors present an analysis of electromagnetic coupling between a twin-lead transmission line and a dipole element. An analysis of the coupling between a transmission line and a linear array of dipole elements over a ground plane has also been developed. The calculated data compared with the measured data favorably. A development of microstrip-line signal injectors embedded in an aperture of a 2D array of monopole excited parallel-plate waveguides has also been made. Measurements of the feed and aperture distributions have been made and the measured distributions follow the designed feed distribution closely View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The output SINR of the linearly constrained beamformer

    Page(s): 1462 - 1464
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB)  

    The authors derive expressions of the output signal-to-interference plus noise ratio (SINR) of the linearly constrained narrowband beamformer in noncoherent situations using a vector approach. Numerical results are included 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