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Microwaves, Antennas and Propagation, IEE Proceedings

Issue 3 • Date June 1999

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Displaying Results 1 - 13 of 13
  • Input impedance of integrated elliptical lens antennas

    Page(s): 181 - 186
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (493 KB)  

    An efficient method is presented for prediction of the input impedance of integrated elliptical lens antennas, excited by a focal radiator which consists of either a resonant slot or a slot-coupled patch. Simple equivalent networks are derived from this method which accounts for effects of multiple reflections inside the lens, which is useful for CAD purposes. Numerical results are presented to validate the equivalent networks. Furthermore, it is shown that these internal reflections significantly affect the input impedance of the primary source. View full abstract»

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  • Complex gyrator circuit of a waveguide junction circulator using an Okada resonator

    Page(s): 197 - 204
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    Conventional waveguide junction circulators usually consist of either a single or a pair of coupled quarter-wave long gyromagnetic resonators in a turnstile arrangement, or a planar post one in contact with the top and bottom walls of the junction of three H-plane waveguides. Another geometry that has much to commend it is that obtained by suppressing the axial resonance in the geometry, using either the single or the pair of coupled quarter-wave long resonators. The complex gyrator circuit of a junction circulator using such a weakly magnetised resonator is approximately developed in terms of effective constitutive parameters and is experimentally verified. The construction of a quarter-wave coupled device is separately described. Circulators using such resonators have been tested at 6000 W-CW at S-band, 1500 W-CW at X-band and 400 W-CW at J-band View full abstract»

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  • Efficient analysis of propagation characteristics of printed cylindrical transmission lines using the non-uniform FDTD technique

    Page(s): 187 - 192
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    A two-dimensional cylindrical, non-uniform finite difference time domain technique is employed in conjunction with an unsplit, anisotropic perfectly matched layer for boundary mesh truncation, for the analysis of printed cylindrical transmission lines. The computed propagation characteristics for both shielded and open structures are found to be in good agreement with the results obtained via the uniform cylindrical FDTD technique. However, the requirements of computation capacity are significantly reduced. It is found that the Gibb's phenomenon corrupts the results, but can be eliminated by using the Blackman-Harris window function to truncate and modulate the time domain signatures View full abstract»

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  • FDTD analysis of serial corner-fed square patch antennas for single- and dual-polarised applications

    Page(s): 205 - 208
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    The finite-difference time-domain (FDTD) method is developed for the analysis of serial corner-fed square patch antennas. A special technique to model the slanted metallic boundaries of the patch antenna has been used in the general FDTD algorithm to avoid the staircase approximations. The method improves the accuracy of the original FDTD algorithm without increasing its complexity. Both the one-port and two-port cases are studied, which are for single- and dual-polarised applications, respectively. Several antenna elements are manufactured. An isolation of -25 dB is achieved by the two-port antenna, which makes it suitable for many dual-polarised applications. The numerical analysis is confirmed by the experimental results and by results published elsewhere View full abstract»

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  • Finite element formulation for the electromagnetic analysis of a metallic wedge arbitrarily loaded and shaped near the edge

    Page(s): 175 - 180
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    A hybrid finite element/boundary element method is presented for near and far field scattering by a perfectly conducting wedge, arbitrarily shaped and loaded near the edge illuminated either by a line source at a finite distance or by a plane wave. The solution is applicable when analysing a thick dielectric corrugated screen, corrugated curved edge, non-uniform loaded wedge and small cylindrical lenses fed by a parallel plate waveguide. Numerical results are presented for both TEz and TMz polarisations and then they are satisfactorily checked against both analytical and numerical results View full abstract»

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  • Mixed integration method for the evaluation of the reaction integrals using the spectral domain method

    Page(s): 214 - 218
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    The spectral domain approach is frequently used for the full-wave analysis of planar structures. Applying Galerkin's method, infinite, double integrals have to be solved. The paper deals with an effective algorithm for solving these integrals using a mixed integration method View full abstract»

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  • Scattering from frequency selective surfaces: a continuity condition for entire domain basis functions and an improved set of basis functions for crossed dipoles

    Page(s): 234 - 240
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (452 KB)  

    A plane wave impinges on an infinite, plane frequency selective surface (FSS) composed of crossed dipoles, and a surface current is induced on the conducting parts of the FSS. Using the established spectral Galerkin method, where the method of moment (MoM) procedure is carried out in the spectral domain, the induced current is determined, and the scattering problem is solved. The authors derive a necessary continuity condition of entire domain basis functions, and show that basis functions which do not satisfy this condition are suppressed by the spectral Galerkin method. Specifically, an improved set of basis functions are presented, designed for crossed dipoles. This set of basis functions consists of traditional even (symmetric) dipole basis functions, and a new set of V-dipole basis functions. It is found that the present basis functions are considerably more efficient than the existing basis functions for crossed dipoles. It is found that it suffices to take four of the present basis functions into account, still getting highly accurate results, even above the first resonance frequency View full abstract»

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  • Characterisation of planar passive circuits using source method and different trial functions

    Page(s): 209 - 213
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    A source method is developed for analysing discontinuities in planar microstrip circuits. It is proposed to model the circuit by rigorous methods including the source method and using different sets of trial functions; roof top, sinusoidal function and an entire trial function. These numerical functions are computed by determining the TE-TM modes of a ridged waveguide using the transverse method. The performance of each set of trial functions used with the source method is evaluated. The numerical results obtained, giving the transmission and reflection coefficients for STEP discontinuities, are compared with previously published data View full abstract»

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  • Parametric study of the coupling aperture in CPW-fed microstrip antennas

    Page(s): 169 - 174
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    Coplanar-fed microstrip patch antennas with inductive and capacitive coupling are extensively studied with the help of a numerical model. The distribution of magnetic current in the apertures is used to explain the coupling mechanism between the aperture and the patch. The inductive coupling is shown to be dependent on the aperture length and the aperture width, while the capacitive coupling is very sensitive to the feeding line dimensions. The influence of a patch shift over the aperture is also investigated View full abstract»

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  • Design of tunable modes and dual-band circular patch antenna using shorting posts

    Page(s): 224 - 228
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    A simple analysis tool is presented, which can predict the resonant frequencies of all normal modes of a circular patch radiator when loaded with a number of passive conducting posts, distributed along the circumference of a circle concentric with the patch radiator. Two specific cases are investigated, where either the resonant frequencies can be tuned in a predictable manner or a closely spaced dual-band antenna with flexible band separation can be designed. It is also shown that for a perturbed circular patch TM01 is the mode with lowest non-zero resonant frequency View full abstract»

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  • Improved scattering analysis of arbitrary-shaped cylinders in a focused beam system using Gabor representation

    Page(s): 193 - 196
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    The Gabor expansion is used to reconstruct the scattering pattern and the induced field ratio (IFR) of an arbitrarily-shaped cylinder measured in a focused beam system. The fields of the transmitting and receiving antennas in the measurement system are described by equivalent fundamental Gaussian beams. The results obtained by the proposed method agree well with the scattering characteristics computed analytically or numerically by the method of moments (MoM), finite elements method (FEM) and by a previous method of analysis using an FFT algorithm View full abstract»

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  • Lumped-element switchable superconducting filters

    Page(s): 229 - 233
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    A switchable superconducting band-stop filter consisting of a series of LC resonators is described. Each resonator can be switched on or off using a bias current to control the superconducting-to-normal resistance transition. The bandwidth of the filter can thus be varied in steps. In each LC resonator, the magnetic field of the inductor passes through the fingers of the interdigital capacitor, and so a simple model is developed for the combined structure. The LC sections are placed in a coplanar line, but the model can easily be adapted to other types of transmission line. Experimental results are given View full abstract»

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  • Slot-coupled back-to-back microstrip antenna with an omni- or a bi-directional radiation pattern

    Page(s): 219 - 223
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    A new slot-coupled back-to-back microstrip antenna is proposed. Two rectangular patches are arranged relative to a slot on the ground plane. The proposed microstrip antenna has an omnidirectional or a bi-directional radiation pattern in the horizontal plane. The characteristics of the proposed antenna were clarified by experiments. The input impedances and radiation patterns were measured as a parameter of the length of various slots. Good input impedances and radiation patterns were obtained. The mechanism to realise these radiation patterns was clarified by using an electromagnetic simulator. The application of the proposed antenna to obtain a circularly polarised bi-directional radiation pattern is also described View full abstract»

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