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A dispersion model for shielded microstrip lines is given here for the first time. This model is valid for a wide range of values of frequency, geometrical parameters and of relative dielectric constants. Unlike previous models for open microstrip lines, the inflection frequency of the dispersion curve has been shown to be a polynomial of the frequency at which the quasi TEM mode of the microstrip...
This paper provides an accurate and computationally efficient method for the analysis of aperture coupling from microstrip to microstrip which is of significant interest in applications involving multilayered media. The accuracy of this method is ensured by satisfying all the boundary conditions through a mixed electric-magnetic current integral equation formulation, combined with the moment method...
This paper presents a new type of microstrip bandpass filter. It is realized in a double-layer configuration, as shown in fig. 1. This design makes use of the vertical dimension to achieve a size reduction over conventional microstrip parallel coupled bandpass filters [1]. These conventional filters have significant overall widths because the widths depend on the number of coupling sections. Also,...
This paper studies the optimum via through a ground plane hole connecting microstriplines on both sides. The via and hole are a discontinuity along the microstrip lines, therefore an optimum via is one that causes the least amount of reflection. Through the use of quasi-static theory on the fringe fields, the optimum radii of the via and the hole are found. These radii give an √L/C ratio of the discontinuity...
In [1], a new method has been developed to minimize the cost and memory requirements of the integral equation method (IEM) for the capacitance calculation of multiconductor system embedded in a homogeneous dielectric medium. In this paper, the method has been extended to the calculation of the capacitance matrix for integrated circuits applications.
A wire grid model has been used to numerically model a 6 m long TEM cell with the Numerical Electromagnetic Code (NEC) [1]. Difficulties in modelling a solid metal structure as a series of wires are discussed. The onset of the various TEnmp and TMnmp modes and their overall field distributions are predicted. Comparison of the TEM field distribution is made to that determined by an independent Moment...
Some aspects of synthesising and analysing dielectric lens antenna are considered in this paper. The suitability of the spherical and shaped lenses to generate simultaneous multiple beams is investigated using the analysis technique developed.
Shaped reflector antennas are capable of producing desired coverage contours on earth by using a single horn thereby avoiding the need for complicated feed arrays and associated beamforming networks (BFNs). The advantages of shaped reflector technology for SATCOM antennas are lower cost, reduced mass and shorter delivery schedule. Development results of a dual-gridded shaped reflector designed for...
Fixed coverage contour beam antennas for geo-stationary satellites can be obtained employing a shaped reflector illuminated by a single feed. Needless to emphasize, this offers a highly attractive alternative to reflector antennas illuminated by an array of feeds. The stringent specifications on the gain slope within the coverage contour and the isolation outside the coverage contour call for suitable...
A Moment Method analysis of a typical circular waveguide polarizer module is described in this paper. The method uses complete sets of entire domain basis and testing functions which provide a high accuracy in the predicted complex scattered fields. Precision design of polarizers can be achieved using this algorithm. Predicted results for a design example are presented.
This paper describes parametric relationships that affect the design of high gain multibeam antennas, discusses tradeoffs, and presents optimized performance of two candidate antennas for wide-angle coverage Advanced Satcom: an aperiodic array with suppressed grating lobes and reduced number of elements, and a side-fed offset Cassegrain system with low scan loss. Given basic performance requirements...
Multiple beam antennas (MBA) for satellite communications usually provide a contiguous coverage over a specified field-of-view by using high gain overlapping spot beams. The common design objective for all MBAs is to maximize the minimum gain within the coverage region. If the MBA has uniform beams arranged in a hexagonal grid, the minimum gain occurs at the triple beam cross-over and the gain variation...
Complex propagation characteristics of composite nonradiative dielectric waveguides (NRD) are presented. Dielectric and ohmic losses are considered in this hybrid mode analysis based on the frequency-domain transmission-line matrix approach. Numerical results of mode dispersion characteristics indicate that a class of complex modes in both lossless and lossy cases may be supported in the composite...
The direct way of evaluating spectral domain Green's functions in the spectral domain moment method is to expand electromagnetic wave modes in each dielectric layer and match the boundary conditions at layer interfaces to obtain unknown coefficients. For multi-layer structures, this leads to a very lengthy derivation process. In [1], an immitance approach is proposed to derive the spectral domain...
For a multilayer medium, the complex images give a simple but accurate approximation to the spatial Green's functions when transformed from the known analytical spectral Green's functions. For a medium with many layers, the latter are tedious to derive. This paper sidesteps the problem by evaluating directly from the constituent simple transmission matrices of an equivalent cascading transmission...
The equivalence principle and the moment method are used to present a solution for the scattering matrix when a number of waveguide junctions (more than one) are considered together in a cascade. This solution presents each two consecutive waveguide junctions by their scattering matrix. The overall scattering matrix of a cascade of waveguide junctions can be obtained by the multiplication of the scattering...
A new Full Wave Finite Difference (FWFD) is proposed which is capable of evaluating field patterns of guided wave structures simultaneously and efficiently. Unlike the traditional finite difefrence methods, its formulation is based on all six vector field components.
Vichniac has stated that “Exact numerical reversibility yields instability in the presence of an attractor” [1]. Vichniac's statement relates the reversibility of an algorithm (i.e., its ability to preserve the information encoded in its initial conditions) to the dynamics of an attractor. In this paper, the relevance of Vichniac's statement to the time-domain numerical methods applied to model electromagnetic...
There are many ways to apply the finite difference method to the time domain Maxwell equations. One of the first applications was the time-space centered algorithm formulated by Yee [1] which is now usually refered to as the finite difference time domain (FDTD) method. In this paper we will be using the term FDTD in the more general sense to include any other finite difference technique which can...
Input impedance of truncated coaxial cable is of considerable importance both from the calibration standard and non-destructive testing points of view. Significant effort has been expended in their analysis [1-3] in order to understand and exploit the fringing field effects. For a calibration standard knowledge of the fringing fields is essential to determine the additional frequency dependent capacitance...
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