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Microwaves, Antennas and Propagation, IEE Proceedings

Issue 6 • Date Dec 1998

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Displaying Results 1 - 14 of 14
  • Contents

    Page(s): 0_6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (56 KB)  

    First Page of the Article
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  • FDTD analysis of EM wave circulated by a magnetised ferrite body of arbitrary shape

    Page(s): 433 - 440
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    An efficient numerical method has been devised for the study of a wave circulated by a magnetised ferrite body of an arbitrary shape. It is a finite-difference time-domain formulation that incorporates Mur's (1981) absorbing boundary conditions and a perfectly matched layer. Several shapes of interest have been studied, including spheres and circular cylinders. The electromagnetic fields inside the ferrite and the power-density distribution on the ferrite's surface normal to the bias external magnetic field are obtained. It is observed that an incident wave would circulate around the magnetised ferrite body in an open space as if the ferrite were placed inside a waveguide junction circulator. The technique is also extended to analyse the electrical performance of waveguide junction circulators. Various wave circulation characteristics are examined, and good agreement is observed between the numerical results and the measured data View full abstract»

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  • Power amplifier module combined with duplexer CDMA-based PCS phone

    Page(s): 486 - 490
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    A power amplifier combined with duplexer is presented for the CDMA-based PCS phone. For reducing idle currents and the overall size of the combined module, dielectric filters in the duplexer are rearranged into a power amplifier to reduce the output power level of the module. The DC bias point is limited to class B. About a 50 mA idle current has been successfully saved, and more current has been saved in the hand phone owing to the reduced power level of the module. The module size has been reduced to 1.5 CC. ACPR performances are satisfactory at the maximum output power of a power amplifier required by IS-95 air interface standards View full abstract»

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  • Procedure for analysis of microstrip patch antennas using the method of moments

    Page(s): 455 - 459
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    Microstrip patch antenna analysis on a finite size model of the dielectric substrate is proposed and investigated using the method of moments. The surface-patch dipole modes are used to model the arbitrarily shaped microstrip patch while the volume polarisation current theorem with rectangular volume cells is used to model the dielectric. Galerkin's solution is applied except at the edges of the patch. Various copper patches have been tested experimentally. The results of the measurement are in good agreement with the computations View full abstract»

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  • Numerical computation of complex image Green's functions for multilayer dielectric media: near-field zone and the interface region

    Page(s): 449 - 454
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    The paper is primarily concerned with the problems arising in connection with the complex image Green's function computation in the near-field zone and over the interface in multilayer dielectric media. The numerical difficulties are investigated related to the cases where the source and observation points are located along an axis perpendicular to the lamination and the observation point is located on the interface between two dielectric media. Methods for resolving these difficulties when using complex image representations are presented. For near-field computation a range is determined within which the surface waves must not be extracted from the spectral representation. Over the interface plane, to obtain a more accurate result, the complex images should be placed in the medium identical to the unbounded region or the medium with a lower dielectric constant View full abstract»

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  • Large-domain integral-equation method for analysis of general 3 D electromagnetic structures

    Page(s): 491 - 495
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    A highly efficient, PC-oriented large-domain method is proposed for the analysis and CAD of a wide class of complex electromagnetic structures. The structures can be any combination of dielectric bodies, conducting surfaces and wires. The bodies are approximated by trilinear hexahedrons (distorted bricks), the surfaces by bilinear quadrilaterals (distorted rectangles) and the wires by straight-wire segments. Current distribution in the elements is approximated by high-order polynomials in local parametric co-ordinates, enabling electrically large elements. All elements can have any distributed impedance loading. In addition, the structure can have lumped loading and generators of several kinds. The unknown current-distribution coefficients are determined by a Galerkin-type solution of a system of coupled integral equations. The principal advantage of the proposed method over existing methods is its generality combined with a comparatively small number of unknowns required for a given problem. The accuracy and versatility of the method are illustrated by a number of examples where analytical or experimental results are available View full abstract»

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  • Use of Coifman intervallic wavelets in 2-D and 3-D scattering problems

    Page(s): 471 - 480
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    The method of moments (MOM) has been used to solve antenna and scattering problems for several decades, due both to its in handling and to its for electrically large problems, the MOM often becomes incapable of achieving solutions due to its requirements for vast amounts of local memory and processor cycles. To overcome this difficulty, orthonormal wavelets have been introduced, which create very sparse moment matrices that can be evaluated by iterative techniques. Nevertheless, the traditional orthonormal wavelets have demonstrated several limitations. The use of intervallic wavelets is presented; they form an orthonormal basis and preserve the same multi-resolution analysis as other unbounded wavelets. In contrast to periodic wavelets, endpoint values are not restricted if the function is expanded in terms of wavelets. Very sparse impedance matrices have been obtained with this method. Zero elements of the matrices are identified directly, without using a truncation scheme with an artificially established threshold. The majority of matrix elements are evaluated directly, without performing numerical integration procedures such as Gaussian quadrature. The construction of intervallic wavelets is presented. Numerical examples of 2-D and 3-D scattering problems are discussed, and the relative error of this method is studied analytically View full abstract»

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  • Design procedure for FSS with wide transmission band and rapid rolloff

    Page(s): 508 - 510
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    An aspect of the Fabry Perot interferometer (FPI) approach to designing frequency selective surfaces (FSS) consisting of cascaded layers is applied to the problem of broadening the transmission band while simultaneously maintaining a rapid rolloff to the reflection region of the transmission response. The technique is to bring the pathlength phase and boundary reflectivity phase curves close to coincidence over the required frequency range. The example used is a two-layer semi-airspaced structure, with the resulting design validated experimentally View full abstract»

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  • Field theory based design and comparison of two kinds of quasi-planar bandpass filters

    Page(s): 441 - 448
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (680 KB)  

    The paper presents a rigorous algorithm for the electrodynamical analysis and design of two kinds of E-plane waveguide quasi-planar filters. The theoretical analysis is based on the scattering matrix with the spectral-domain approach and space-domain integral equation method. The principal feature of the method consists of utilisation of complete sets of adequate basis functions corresponding to the field behaviour near the metal and dielectric discontinuities of the filter structures. Numerical and experimental results are shown for K-band bandpass filters. The calculated results agree well with experimental data View full abstract»

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  • Triangular-patch model of bowtie antennas: validation against Brown and Woodward

    Page(s): 465 - 470
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    The input impedance and field patterns for bowtie antennas of various lengths and flare angles have been calculated using the moment method and triangular basis functions. These agree within 10% of previous experimental results. Rao-Wilton-Glisson (1982) basis functions, delta-gap feed and Caorsi's (1993) line-integral method were used View full abstract»

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  • Optimisation of synthesised array excitations using array polynome complex root swapping and genetic algorithms

    Page(s): 460 - 464
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    A numerical pattern synthesis optimisation technique for shaped and sidelobe beams adhering to desired array element excitations are described. The synthesis approach is a modification of the Woodward synthesis method with an additional sidelobe minimisation, and the final element excitation optimisation is based on array polynome complex root swapping and genetic algorithms. These methods have been applied to an equispaced linear planar array. Results of the synthesis and genetic algorithms are presented View full abstract»

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  • Modal analysis at the junction formed by a circular or an elliptic waveguide and a translated and rotated elliptic waveguide

    Page(s): 501 - 507
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    The scattering characteristics of waveguide junctions with a smaller off-centred elliptic waveguide are analysed using the mode-matching method. Two types of junction are considered, where the larger waveguide that forms the junction is circular or elliptic in cross-section. General cases are studied that include both translational and rotational displacement between the waveguides. Using generalised expressions for the coupling coefficients, together with the addition theorem for Mathieu functions, series form solutions for evaluating the coupling integrals have been derived. For circular-to-elliptic junctions, an efficient method is shown for recomputing the coupling matrix due to an additional rotation between the waveguides View full abstract»

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  • Inductance computation for coplanar waveguide discontinuities with finite metallisation thickness

    Page(s): 496 - 500
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    A variational formula in terms of the magnetic flux density is proposed in the inductance computations for coplanar waveguide (CPW) structures with finite metallisation thickness. Introducing Lagrange multipliers, the variational equation is solved by the hybrid finite-element method. Numerical results for the equivalent short-end inductance are presented and compared with published data. When the thickness is small the variational equation can be reduced to a perturbation formula involving the normal magnetic flux density which is available in the inductance computation for a CPW with zero thickness. The errors due to this approximation are investigated by comparing the results with those by the more accurate hybrid finite-element method. Numerical results for extensive discontinuities are presented by employing the perturbation formula View full abstract»

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  • Design of corner reflector antennas using FDTD

    Page(s): 481 - 485
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    A design study of the corner reflector antenna is reported, using the finite difference time domain (FDTD) method, which takes account of the finite size of the corner reflector plates. The influence of the geometric parameters on the radiation characteristic is established, and optimum design information is presented. The method has been validated by constructing and measuring an experimental antenna, which gives results in very good agreement with the predictions View full abstract»

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