Showing papers in "Electromagnetics in 1989"
TL;DR: In this paper, the analysis of a microstrip patch antenna with an electrically thick substrate is performed using a mixed potential integral equation (MPE) based on the coaxial probe, thus eliminating the often used thin substrate approximations.
Abstract: The analysis of a microstrip patch antenna with an electrically thick substrate is performed using a mixed potential integral equation. Basis functions are employed on the coaxial probe thus eliminating the often used thin substrate approximations. There is no theoretical limit to the thickness of the structures that can be analyzed. A special attachment mode, employed at the coaxial probe-antenna junction, is introduced. Measured and calculated input impedance results for isolated rectangular microstrip antennas are compared.
43 citations
TL;DR: An analysis of electromagnetic scattering by an arbitrarily shaped anisotropic, but homogeneous material structure utilizing combined field surface integral equation formulation is presented in this article, where the appropriate electromagnetic potentials along with their appropriate gauges are used to represent the fields in the medium.
Abstract: An analysis of electromagnetic scattering by an arbitrarily shaped anisotropic, but homogeneous material structure utilizing combined field surface integral equation formulation is presented Derivation of the appropriate electromagnetic potentials for the time harmonic Maxwell's equations is also undertaken The medium in this study is characterized by its permittivity and permeability tensors, and the mathematical formulation is specialized to the two-dimensional anisotropic scatterer of arbitrary shape excited by a plane wave at normal incidence The derived potentials along with their appropriate gauges are used to represent the fields in the medium Subsequently, these field representations are utilized in the derivation of a set of coupled integral equations with the help of the equivalence principle Rigorous analysis approach is developed for the two-dimensional objects, both for the TM and the TE polarizations
36 citations
TL;DR: In this article, an accurate and efficient numerical algorithm for the computation of the near-field characteristics of microstrip elements on cylindrical substrates is presented, which is applicable for any homogeneous, isotropic, and linear substrate material, including lossy materials of arbitrary substrate thickness.
Abstract: A highly accurate and efficient numerical algorithm for the computation of the near-field characteristics of microstrip elements on cylindrical substrates is presented in this paper. The algorithm is applicable for any homogeneous, isotropic, and linear substrate material, including lossy materials of arbitrary substrate thickness. The numerical and mathematical limiting cases, such as the low or high frequency limits, are described analytically and numerically to illustrate the functional behavior of the cylindrical Green's function.
19 citations
TL;DR: In this paper, the authors present a methodology for the computation of the response of a multiconductor transmission line terminated by linear networks to an arbitrary excitation in a multilayered homogeneous lossy dielectric media.
Abstract: The objective of this paper is to present a methodology for the computation of the response of a multiconductor transmission line terminated by linear networks to an arbitrary excitation. The lines are embedded in multilayered homogeneous lossy dielectric media and have uniform cross sections along their lengths. To check the accuracy of the theoretical results, extensive experimental verification has been carried out.
16 citations
TL;DR: In this paper, the authors considered the case that the second object is symmetrical with respect to the first with a plane of symmetry between them, and a perturbation of the natural frequencies was found which is applicable to an intermediate range of spacing between them.
Abstract: Given the natural frequencies of an object (electromagnetic scatterer) in free space, one can consider how they are changed by the presence of another object in its proximity. This paper considers the case that the second object is symmetrical with respect to the first with a plane of symmetry between them. A perturbation of the natural frequencies is found which is applicable to an intermediate range of spacing between them.
16 citations
TL;DR: In this article, a semi-infinite layer of a non-magnetic dielectric material is modelled using a combination of resistive and (modified) conductive sheets, and for the problem of a plane wave at skew incidence on the resulting half-plane, the exact solution is determined by the Wiener-Hopf technique.
Abstract: A thin semi-infinite layer of a non-magnetic dielectric material is modelled using a combination of resistive and (modified) conductive sheets, and for the problem of a plane wave at skew incidence on the resulting half-plane, the exact solution is determined by the Wiener-Hopf technique. The far zone diffracted field is then derived and expressed in the form of an edge diffraction tensor.
9 citations
TL;DR: A companion formulation, based on matrix partitioning, is used in this work to compare the “Add-On” technique with the matrix formulation, and it is shown that the two formulations yield the same results.
Abstract: For large scatterers whose operator is discretized by a prohibitively large matrix. It may be advisable to build the solution in a gradual manner while relying on previously known information on a portion of the body. In this way, rather than analyzing the large composite body, a succession of calculations of small additions is carried out, starting at the point where the partial solution is known. The “Add On” method, introduced recently, has done this successfully for a number of large planar problems. The method reconstructs the matrix solution without building the entire matrix up and without inverting It. A companion formulation, based on matrix partitioning, is used in this work to compare the “Add-On” technique with the matrix formulation. It is shown that the two formulations yield the same results. However, the numerical advantages of the “Add On” technique are clearly shown, especially with regard to storage problems, since the full N × N matrix need not be generated and stored. Instead...
9 citations
TL;DR: In this article, the problem of a plane wave incident on a coated right-angled wedge is considered and a solution is derived using an extension of Maliuzhinets' method in which a key role is played by the particular solution of the difference equation for the spectral function.
Abstract: By using a second order generalized impedance boundary condition to model the effect of a thin dielectric coating, the problem of a plane wave incident on a coated right-angled wedge is considered. The solution is derived using an extension of Maliuzhinets' method in which a key role is played by the particular solution of the difference equation for the spectral function. It is verified that the field satisfies the reciprocity and edge conditions, and the diffracted, geometrical optics and surface wave contributions are determined.
6 citations
TL;DR: The SSFIP (Strip - Slot - Foam - Inverted Patch) antenna concept provides a broad frequency bandwidth, with high efficiency, a very low crosspolarisation level and an integrated radome as mentioned in this paper.
Abstract: The SSFIP (Strip - Slot - Foam - Inverted Patch) antenna concept provides a broad frequency bandwidth, with high efficiency, a very low crosspolarisation level and an integrated radome. It is lightweight, rigid and inexpensive. Single patch and stacked antennas yielded respectively 13.2% and 33% bandwidths, both for a VSWR lower than 2:1. These results open new possibilities and applications to planar antennas.
5 citations
TL;DR: In this paper, the authors considered the response of electric and magnetic field sensors in terms of spherical modal expansions to identify the electric-and magnetic-dipole terms which are associated with the ideal angular response to an incident plane wave.
Abstract: This paper considers the response of electric- and magnetic-field sensors in terms of spherical modal expansions to identify the electric-and magnetic-dipole terms which are associated with the ideal angular response to an incident plane wave. Considering an idealized spherical resistive sheet sensor, the dipole surface current densities are computed and bandwidth and figure of merit determined to optimize the choice of Rs. For practical sensors the response in general includes various multipole terms besides the desired dipole terms. Expanding the response in terms of spherical harmonics allows one to identify the dipole term and from this gives one a definition of upper frequency response. In addition a norm over the unit sphere of the difference between the actual response and the ideal response gives another way to define upper frequency response. An example of a magnetic -sensor design which approximates the resistive-sheet sphere is also considered.
5 citations
TL;DR: In this article, a moment method solution of a rectangular microstrip radiator is presented, which incorporates a special treatment of the current singularities at the feed and at the edges of the patch.
Abstract: A moment method solution of a rectangular microstrip radiator is presented. This solution incorporates a special treatment of the current singularities at the feed and at the edges of the patch. The two dimensional distribution of the surface current vector on the microstrip radiator is obtained by a fast convergent computational procedure. A comprehensive set of computed results for the current density on the radiator is presented and discussed.
TL;DR: In this paper, a numerical technique for computing transverse magnetic scattering by perfectly conducting wedges and half-planes coated with dielectric and/or magnetic materials is presented, which combines finite element method with surface integral equation and physical optics formulations.
Abstract: A numerical technique is presented for computing transverse magnetic (TM) scattering by perfectly conducting wedges and half-planes coated with dielectric and/or magnetic materials. The technique combines finite element method with surface integral equation and physical optics formulations. Example results are presented for surface fields from which the corresponding surface impedances are calculated.
TL;DR: In this paper, an analysis of isosceles triangular patch antennas with various apex angles is presented, where the patch is modeled as a leaky radial line terminated by a radiation impedance and theoretical results yield good agreement with experimental data available in the literature.
Abstract: An analysis of triangular patch antennas is presented. The patch is modeled as a leaky radial line terminated by a radiation impedance. Impedance characteristics of isosceles triangular patch antennas with various apex angles are shown. Theoretical results yield good agreement with experimental data available in the literature.
TL;DR: This paper reviews the recently developed multiport network modeling approach for the analysis and the design of microstrip patch antennas, where the fields in the interior and the exterior of the patch are modeled by separate multiport subnetworks.
Abstract: This paper reviews the recently developed multiport network modeling approach for the analysis and the design of microstrip patch antennas. In this approach, the fields in the interior and the exte...
TL;DR: In this article, Lie algebra techniques are used to generate new nonseparable exact solutions to the two-dimensional Helmholtz equation, which are then used to solve the problem.
Abstract: In this paper. Lie algebra techniques are used to generate new nonseparable exact solutions to the two-dimensional Helmholtz equation. While certain classes of nonseparable solutions have been foun...
TL;DR: In this article, the characteristics of printed antennas in a two-layer anisotropic substrate are investigated, including input impedance of a ceneter-fed dipole, radiation efficiency, antenna gain and radiation patterns.
Abstract: The characteristics of printed antennas in a two-layer anisotropic substrate are investigated This includes input impedance of a ceneter-fed dipole, radiation efficiency, antenna gain and radiation patterns The analysis adopts the moment method solution of the integral equation where various numerical techniques are applied to enhance the computational efficiency The effects of substrate and superstrate anisotropy on the antenna characteristics are also described
TL;DR: In this article, the effects of parasitic size effects on two and three layer EMCP antennas and the superstrate effects on the two-layer EMCP antenna were investigated in detail, both for the broadband and high-gain regions.
Abstract: This paper presents experimental results of parasitic size effects on two and three layer electromagnetic coupled patch (EMCP) antennas and the superstrate effects on the two layer EMCP antenna. The effects on pattern characteristics, resonant frequency, resonant input resistance and impedance bandwidth of the TM01 mode are investigated in detail, both for the broadband (closely spaced) region and for the high-gain (widely spaced) region. The patches are rectangular and are fabricated on Cuflon substrate (er = 2.17), with the dimensions of the fed patch fixed at 1.5 x 1.0 cm. The resonant frequency of the TM01 mode is approximately 10 GHz. Among the many results obtained, the following are of particular interest:
TL;DR: In this article, the propagation in a non-linear dispersive medium is analyzed by using differential equation techniques, based on transform time dependent Maxwell equations into a slowly varying envelope function differential equation.
Abstract: The propagation in a non-linear dispersive medium is analysed by using differential equation techniques. A dispersive semi-infinite space with a cubic order instantaneous non linearity, is considered. The proposed analysis is based on to transform time dependent Maxwell equations into a slowly varying envelope function differential equation. The derived partial differential equation has many similarities with the so-called Schrodinger equation but it includes an additional term arising from the first order dispersion. This non-linear equation is solved by application of the Inverse Scattering Method for the initial condition |q(x,t = O)| = Asechx. The N-soliton solution is developed analytically in the case of reflectionless potentials. The single and double soliton solution are derived explicitly. Numerical results presenting the pulse propagation inside the non-linear dispersive medium are also given.
TL;DR: The EM problem consists of choosing the appropriate sensor type and location on an aircraft such that the scattered fields from the aircraft and the sensor mountings do not significantly couple to the sensor, while measuring the Incident field.
Abstract: This paper deals with the development of an airborne platform for measuring transient or broadband CW electromagnetic (EM) fields. The considerations and guidelines [1] useful in designing such a platform are discussed. The EM problem consists of choosing the appropriate sensor type and location on an aircraft such that the scattered fields from the aircraft and the sensor mountings do not significantly couple to the sensor, while measuring the Incident field. These design considerations were applied In specifically designing a nose boom B-dot sensor for the NASA F-106 B aircraft [2]. Sample experimental results [3] with comparisons to calculated Incident fields are also presented.
TL;DR: In this paper, the radiation patterns of a three-element array of staggered parallel-plate waveguides were calculated by ray-optical methods, and experiments with a long H-plane sectoral horn at about 12 GHz showed good agreement with the theory.
Abstract: The radiation patterns of a three-element array of staggered parallel-plate waveguides is calculated by ray-optical methods. Experiments with a long H-plane sectoral horn at about 12 GHz show good agreement with the theory.
TL;DR: It is shown that computing the derivative of the waveform by Fourier transforming it, using the DFT derivative theorem, and taking the inverse Fourier transform yields a much more accurate approximation to the derivative in the presence of noise than does computing the forward difference.
Abstract: An approach to determining the derivative of a signal which is an exponentially-decaying function of time is presented. The case of a waveform sampled in time is treated. The method is applicable to functions which are complicated combinations of decaying exponentials. Robust behavior in the presence of additive noise is also obtained. It is shown that computing the derivative of the waveform by Fourier transforming it, using the DFT derivative theorem, and taking the inverse Fourier transform yields a much more accurate approximation to the derivative in the presence of noise than does computing the forward difference. A recursive discrete Fourier transform is then used, to permit computing the derivative of a sampled waveform as the samples are taken. A recursive DFT derivative theorem is derived. This is then applied to numerical simulations using a function which is the sum of three unevenly-weighted exponentials with different decay constants, and it is shown that useful results for the deri...
TL;DR: A method for automatic correction of the quantization error in time-interval counters is presented, considering the time jitter as well as the bias error inherent in the counter.
Abstract: A method for automatic correction of the quantization error in time-interval counters is presented. A detailed analysis for Gaussian time-intervals is given for synchronous and asynchronous counting mode, considering the time jitter as well as the bias error inherent in the counter. The usefulness of the method is proved by numerical examples and experimental results.
TL;DR: In this article, the mutual coupling admittance between radiating edges of a microstrip antenna with a dielectric cover layer is obtained by modelling the edge fields as equivalent magnetic currents divided into small sections.
Abstract: The fields due to a magnetic dipole on the ground plane with a dielectric cover are derived. Based on this knowledge, the mutual coupling admittance between radiating edges of a microstrip antenna with a dielectric cover layer is obtained by modelling the edge fields as equivalent magnetic currents divided into small sections. Experimental results verifying the proposed method are presented.
TL;DR: In this paper, the radiation properties of a prime focus feed with multiple coaxial cups were examined with particular emphasis on the level of cross-polarized radiation, and it was demonstrated that by optimizing the feed dimensions, the crosspolarization can be maintained below − − 27 dB over a 20% bandwidth for a feed with a single coaxial cup.
Abstract: The circular waveguide antenna feed with multiple coaxial cups is analyzed using the method of moments. The radiation properties of this type of prime focus feed are examined with particular emphasis on the level of cross-polarized radiation. It is demonstrated that by optimizing the feed dimensions the cross-polarization can be maintained below − 27 dB over a 20% bandwidth for a feed with a single coaxial cup. By examining the effects of various numbers of modes used to approximate the aperture fields it is concluded that quite accurate results can be obtained by including only the TE11 and TM11 modes in each aperture region.
TL;DR: In this article, the Singularity Expansion Method (SEM) parameters for the general tetra-arm structure are calculated for a wide range of geometrical configurations, including planar symmetric tri-arm, L-shaped wire, and straight wire.
Abstract: The Singularity Expansion Method (SEM) parameters (natural frequencies, natural modes, and coupling coefficients) are presented for several different geometries each composed of four arbitrarily-oriented, thin, straight wire scatterers with one end of each of the four straight members connected at a common intersection point. Various choices of the orientations (and lengths) of these four members result In specific configurations which have been investigated previously (perpendicular crossed wires, planar symmetric tri-arm, L-shaped wire, and straight wire) as well as several other configurations which have not (nonplanar symmetric and nonsyrametrlc tetra-arms, nonplanar symmetric and nonsymmetrlc trl-arms, and arbitrarily bent wire). The SEM parameters for the general tetra-arm structure are calculated for a wide range of geometrical configurations. Commonalities which exist between the SEM parameters of the general tetra-arm scatterer and the previously analyzed “dipoles”, “tripoles” and “cross...