Moment-method analysis of printed circular wire-loop antenna usingcurved piecewise sinusoidal subdomain basis and test functions

A computationally efficient method for analyzing printed wire-loop antennas on grounded dielectric substrates which uses curved piecewise sinusoidal subdomain current basis and test functions spanning two segments in a moment-method solution to Pocklington's equation is presented. Results for loop-input impedances are convergent, and these, together with efficiencies, compare favorably with computations using entire domain and linear subdomain basis and test functions     

A method of moments approach for the efficient and accuratemodeling of moderately thick cylindrical wire antennas

This paper introduces a moment-method formulation, which is capable of accurately modeling moderately thick cylindrical wire antennas. New algorithms are presented for the efficient computation of the cylindrical wire kernel and related impedance matrix integrals. These algorithms make use of exact series representations as well as efficient numerical procedures and lead to a significant reduction in overall computation time for thicker wires. Another major advantage of this moment-method technique is that it is no longer restricted by the segment length-to-radius ratio limitations inherent in past formulations, thereby making it possible to achieve solution convergence for a much wider class of wire antenna structures. Several examples illustrating the superior convergence properties of this new moment-method formulation are presented and discussed     

Full-wave spectral analysis and design of annular patch antenna with electromagnetically coupled microstrip feed line

This paper presents a full-wave analysis, and the ensuing design considerations, of the annular patch antenna fed by an electromagnetically coupled microstrip line. The numerical analysis employs the spectral domain version of the integral equation, with the method of moments formulation; the basis functions on the ring patch are the eigenmodes of the corresponding magnetic wall cavity, and subsectional (rooftop) functions are employed on the access line. Both TM and TE modes are used, along with more-efficient "collective" solenoidal modes; mode sorting criteria are given to ensure uniform convergence. Efficient schemes are presented for the calculation of the spectral-domain reaction integrals, along with criteria to avoid calculation of negligible mode-to-mode couplings, based on the spectral analysis of the matrix condition number. Very good agreement is shown with measured data, and design considerations are given for matching the radiator.     

Analysis of stripline-fed slot-coupled patch antennas with vias forparallel-plate mode suppression

The paper presents an analysis of slot-coupled stripline-fed patch antennas with vias around the slot to minimize the power launched into the parallel-plate mode. A moment-method scattering formulation is invoked to include the effect of vias on the impedance characteristics of the antenna. Coupling between the stripline feed and the ground-plane slot is obtained by invoking reciprocity. Two design examples were fabricated and the measured input impedances verify the accuracy of the analysis. Vias considerably modify the impedance and resonant characteristics of a patch antenna. The radiation efficiency of patch antennas with and without vias is studied and proper location of the vias is shown to drastically reduce power in the parallel-plate mode     

Moment-method analysis of large, axially symmetric reflectorantennas using entire-domain functions

The moment-method technique utilizing entire domain basis functions is applied to the analysis of large, axially symmetric reflector antennas. The electric surface current is modeled as a finite series of sinusoids whose domain consists of the entire generating curve. This expansion results in a matrix size of less than 5% of that produced with subdomain basis functions. Only a slight increase in the CPU requirements occurs from this analysis. The results from this technique show good agreement when compared to both physical optics and a subdomain-based moment-method formulation on small, axially fed paraboloidal and hyperboloidal reflector antennas. Extension to a large 100-λ paraboloidal reflector with f/D=0.4 produces results comparable to that obtained using physical optics. Convergence is obtained with as few as two expansion terms per wavelength. Discretization of the generating curve with four points per wavelength leads to results which agree within 0.5 dB over data from a more densely defined curve     

Parametric analysis of slot-loaded trapezoidal patch antennas

Slot-loaded trapezoidal patch antennas are analyzed in order to achieve a multifrequency operation. A moment method formulation based on new analytical entire domain basis functions is developed and compared to the one involving the Rao-Wilton-Glisson (1982) RWG triangular discretization. The numerical results obtained through the new efficient implemented code are compared to the measurements showing a good agreement. A parametric analysis of such antennas is also presented leading to useful design graphs showing the main antenna properties (resonance frequencies, cross-polarization levels, matching, etc.) as a function of the patch geometrical dimensions, symmetric collocation of the slots on the patch, and slot dimensions.     

Parallel in-core and out-of-core solution of electrically large problems using the RWG basis functions

Currently, the problem size that can be solved in reasonable time using the Method of Moments is limited by the amount of memory installed in the computer. This paper offers a new development that not only breaks this memory constraint, but also maintains the efficiency of running the problem in-core. In this paper, highly efficient parallel matrix-filling schemes are presented for parallel in-core and parallel out-of-core integral-equation solvers with subdomain RWG basis functions. The parallel methodology for matrix filling is quite different when using a subdomain basis as opposed to using a higher-order basis. The parallel in-core solver uses memory, which is often expensive and limited in size. The parallel out-of-core solver is introduced to extend the capability of MoM to solve larger problems that can be as large as the amount of storage on the hard disk. Numerical results on several typical computer platforms show that the parallel matrix-filling schemes and matrix-equation solvers introduced here are highly efficient and achieve theoretical predictions. The implementation of these advancements with the widely used RWG basis functions creates a powerful tool for efficient computational electromagnetics solution of complex real-world problems.     

Series expansions for the mutual coupling in microstrip patcharrays

A dominant-mode mutual coupling theory is developed for an array of microstrip patches. One of the key features of the formulation is that only values for isolated self- and mutual impedance are needed in the formulation, making the method suitable for either a cavity model or spectral-domain analysis, or compatible with experimental measurements. The formulation is equivalent with D.M. Pozar's (1982) moment-method formulation. A series expansion of the solution is derived, allowing for approximate formulas accurate to any specified order. These formulas do not require matrix inversion. Formulas up to third order require less computation time that the exact solution, for single elements of the impedance, admittance, and scattering matrices. These expansions are computationally efficient for large sparse arrays     

Moment-method analysis of printed wire spirals using curvedpiecewise sinusoidal subdomain basis and testing functions

Archimedian and logarithmic printed wire spirals are analyzed using a moment-method incorporating curved piecewise sinusoidal subdomain basis and testing functions. Results for spiral parameters including input impedance and current distribution are presented and are shown to have good agreement with published results for the same antennas obtained using linear segmentation. Since the curved basis functions exactly follow the spiral contour, significantly fewer curved segments are, therefore, required for accurate analysis compared with linear segmentation     

Entire-domain basis MOM analysis of coupled microstrip transmissionlines

A full-wave spectral-domain integral equation formulation is used to analyze coupled open-boundary microstrip transmission lines. A general rigorous formulation is specialized to the case of two identical uniform lines and a method of moments (MOM) solution is implemented. In contrast with earlier subdomain basis MOM solutions, entire-domain basis functions which incorporate appropriate edge conditions for transverse and longitudinal current components are utilized. This allows closed-form evaluation of relevant spatial integrals and results in improved accuracy using far fewer terms. Numerical results in the form of propagation constants and current distributions are presented for the dominant and first two higher-order coupled modes, and compare favorably to results of other techniques     

Analysis of an infinite phased array of aperture coupled microstrippatches

An analysis of an infinite array of aperture-coupled microstrip patch antennas is described; this type of element is well suited to integrated phased-array applications, offering several advantages over other array configurations. The solution uses the spectral-domain moment-method approach, and combines features of a previous solution of infinite arrays of probe-fed patches and a reciprocity analysis of single-aperture-coupled microstrip element. The theoretical analysis is described and data are presented for the active input impedance of several arrays. Experimental data from a waveguide simulator confirm the theory     

Analysis of waveguides with metal inserts

A systematic analysis of waveguides with metal inserts is presented. The method is based on a field expansion in terms of the normal modes of the corresponding hollow waveguide without metal inserts. The analysis leads to two formulations: a matrix formulation and a moment-method formulation. The matrix formulation is suitable for structures with smooth metal inserts which are free from sharp edges, while the moment method is more suitable for metal sheets (e.g. strips and fins) or metal inserts with sharp edges (e.g. ridges). The validity of the method is tested by investigating some special cases in which the surface of the metal insert coincides with one of the coordinate surfaces, e.g. a bifurcation in circular or rectangular waveguides. The method is then applied to the analysis of striplines and ridge waveguides. It leads to a generalization of the widely used spectral-domain technique in that ridges, fins, and strips with finite thickness can now be analyzed likewise. Any existing routine for the analysis of planar structures which is based on the spectral-domain technique can then be slightly modified in order to take the metallization thickness into account     

A Galerkin moment method for the analysis of an insulated antennain a dissipative dielectric medium

A Galerkin moment method is employed to solve the problem of a dielectric-coated dipole antenna in a dissipative medium. Piecewise sinusoids are used as basis and testing functions. The dielectric coating is modeled by equivalent-volume polarization currents, which are simply related to the conduction current distribution. No additional unknowns are introduced, and the size of the moment-method matrix is the same as that for bare antennas. Exact and approximate formulas for the near electric field are derived. The computed results exhibit excellent agreement with those previously published for a symmetric, as well as an asymmetric insulated dipole. Compared to its existing competitors, the new method appears to be more general and computationally efficient     

A doubly periodic moment method solution for the analysis anddesign of an absorber covered wall

A periodic moment-method solution for scattering from a doubly periodic array of lossy dielectric bodies is developed. The purpose is to design electromagnetic wedge and pyramidal absorbers for low reflectivity so that one can improve the performance of anechoic chamber measurements. The spectral-domain formulation and the moment-method volume polarization current approach are used to obtain the expressions for determining the scattering from a doubly periodic array of lossy dielectric bodies. Some wedge and pyramidal absorber configurations that have been designed, fabricated, and tested in the OSU/ESL compact range measurement facility are presented. By taking into account the complexity of real-world material structures, good agreement between calculations and measurements has been obtained     

Limitations of the Cubical Block Model of Man in Calculating SAR Distributions

Block models of man which consist of a limited number of cubical cells are commonly used to predict the internal electromagnetic (EM) fields and specific absorption rate (SAR) distributions inside the human body. Numerical results, for these models, are obtained based on moment-method solutions of the electric-field integral equation (EFIE) with a pulse function being used as the basis for expanding the unknown internal field. In this paper, we first examine the adequacy of the moment-method procedure, with pulse basis functions, to determine SAR distributions in homogeneous models. Calculated results for the SAR distributions in some block models are presented, and the stability of the solutions is discussed. It is shown that, while the moment-method, using pulse basis functions, gives good values for whole-body average SAR, the convergence of the solutions for SAR distributions is questionable. A new technique for improving the spatial resolution of SAR distribution calculations using a different EFIE and Galerkin's method with linear basis functions and polyhedral mathematical cells is also described.     

A study of wavelets for the solution of electromagnetic integralequations

The use of wavelet basis functions for the efficient solution of electromagnetic integral equations is studied. It has previously been demonstrated that the use of wavelets for expansion and testing functions produces a sparse moment-method matrix. Here, this effect is examined and analyzed in terms of the radiation/receiving characteristics of the wavelet basis functions. The limitations of wavelets as an efficient solution technique are discussed, and a comparison is made to other fast algorithms     

Analysis of a slot-coupled T-junction betweencircular-to-rectangular waveguide

This paper presents a rigorous analysis of a slot-coupled T-junction between a primary circular cylindrical waveguide and rectangular waveguide, forming the coupled T-arm. The analysis is based on moment-method formulation using full-wave basis functions and Galerkin's technique for testing. Expression for the coupling and reflection coefficients are found, taking into account the effect of finite wall thickness of the circular waveguide in which the coupling slot is milled. A comparison between the theoretical and experimental results on coupling and return loss are presented     

Designing rectangular patch antenna using the neurospectral method

This paper presents a new method for developing computer-aided design (CAD) models, using spectral domain (SD) formulation. Using the artificial neural network (ANN) technique, a combination of continuous function and delta functions constitutes the spectral domain Green's functions. We obtain closed-form formulas for integration involving these equations. Another neural network relates different antenna parameters. Utilizing the reverse modeling for patch dimension determination, it becomes useful as a CAD model for patch antenna design. Designs, of simple rectangular patch antennas, serve as illustration of this method.     

Electromagnetic radiation from structures consisting of combinedbody of revolution and arbitrary surfaces

A formulation is developed to treat radiation from structures consisting of a body of revolution (BOR) in the presence of multiple arbitrarily shaped three-dimensional objects. An electric field integral equation is set up on the surface of the combined structure. The resulting integro-differential equation is solved using the method of moments. On the BOR, harmonic entire domain expansion functions are used for the circumferential dependence, while overlapping subdomain functions are used to model the axial curvature. The arbitrarily shaped portions of the structure are modeled using triangular surface patches. The resulting system matrix has a partial block diagonal nature, which provides a more economical solution for structures that have some rational symmetry. Numerical results are presented and compared to measurements of a unique cavity-backed patch fed antenna     

Rigorous and efficient full-wave analysis of trapezoidal patchantennas

A rigorous full-wave analysis in the spectral domain for trapezoidal patch antennas is presented. Particularly, a new set of entire domain basis functions for an efficient implementation of the method of moments (MoM) is carried out by properly imposing the boundary conditions. The simulated results obtained through the presented method are compared to the measurements showing a good agreement. Finally, a parametric analysis of the main antenna features (matching, radiation pattern, cross-polarization levels) is also carried out