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Microwaves, Antennas and Propagation, IEE Proceedings

Issue 5 • Date 10 Oct. 2003

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Displaying Results 1 - 16 of 16
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  • Characterisation of discontinuity effects in triple ridge waveguides using 90° and 180° unit elements

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    The discontinuity effect at a step between any two waveguides is an important aspect in the design of impedance steps and filter structures. The purpose of the paper is to characterise the effect between a regular rectangular waveguide and a triple ridge waveguide propagating its dominant mode. One method of achieving this is to employ a 180° UE (unit element) in conjunction with a calculation of the characteristic impedance and wavelength of the ridge waveguide. Another method is to have recourse to its odd-mode eigen-network. Both procedures are employed in order to obtain data on such a discontinuity. Results are in accord with separate calculations using a commercial finite element (FE) solver View full abstract»

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  • Calculation of the input impedance of dipoles in proximity to walls

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    The trend towards microcells is likely to result in more base station antennas being sited on the sides of buildings. However, the presence of the wall affects the antenna's input impedance. This contribution investigates the prediction of this detuning effect using a number of integral equation approaches. The reliability of different approaches is considered and two complex image-based formulations, shown to be especially well suited to this situation, are presented View full abstract»

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  • Effect of diverse anisotropy in multilayer superstrate-substrates on pulse propagation in shielded microstrip lines

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    The effect of anisotropy in multilayer superstrate-substrates on the propagation of a Gaussian pulse and a sinusoidally modulated Gaussian pulse in shielded microstrip lines (MLs) has been examined. Such multilayer superstrate-substrates are made of sapphire, ferrite and perhaps biaxially anisotropic materials, characterised by both tensorial permittivity and permeability. Mathematical treatments used were based on Galerkin's method in the spectral domain and fast Fourier transformation (FFT). Parametric studies were performed to show the effects of various diverse anisotropic occurrences in the superstrate-substrates on pulse distortion, including time delay, ringing and crosstalk between signal and sensing strips. It was shown that pulse distortion could be reduced effectively by combining different anisotropies in superstrates and substrates View full abstract»

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  • Conservation laws for time-domain signals propagating along multiconductor transmission-line structures

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (294 KB)  

    Conservation laws for time-domain signals propagating along general multiconductor transmission-line structures are derived. Conservation of voltage-pulse areas and current-pulse areas are obtained from fundamental principles based directly on Maxwell's equations. Underlying assumptions are described and discussed View full abstract»

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  • Comparison of the use of dual-frequency and single-frequency attenuation for the measurement of path-averaged rainfall along a microwave link

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    It is shown that, for certain combinations of frequency and polarisation, the difference in microwave attenuation between two frequencies along a terrestrial link can give a much better estimate of path-averaged rain rate than can be obtained from a single frequency. An example is given which shows that attenuation difference can successfully provide rainfall estimates in practical applications View full abstract»

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  • Generalised higher-order FDTD-PML algorithm for enhanced analysis of 3D waveguiding EMC structures in curvilinear coordinates

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    A 3D higher-order FDTD methodology for the efficient solution of complicated waveguide EMC problems in non-orthogonal coordinate systems is presented. Introducing a new topological classification of accurate non-standard schemes, the algorithm develops a consistent covariant/contravariant formulation which fulfils the proper continuity conditions and eliminates every critical lattice dispersion error. Moreover, the wider spatial stencils near arbitrarily-curved boundaries are successfully manipulated via self-adaptive compact operators, whereas temporal advancement is performed by a generalised leapfrog approach. Conversely, for the termination of infinite waveguide ends, the proposed higher-order concepts are applied to the systematic construction of reflectionless curvilinear PMLs that can be imposed very close to structural discontinuities. Due to their optimal arrangement and a flexible pulsed-modulated excitation process, these absorbers accomplish substantial attenuation rates, even for laborious domains or broadband frequency spectra. Numerical results addressing diverse multiport waveguides with inclined slots and irises reveal that the novel strategy exhibits superior accuracy and significant savings in computer resources View full abstract»

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  • Polarisation synthesis and beam tilting using a dual port circularly polarised travelling wave antenna array

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    The paper describes the application of a dual port annular sector radiating line antenna (ANSERLIN) element, designed to provide a radiation bandwidth of 35% (1.7 GHz to 2.4 GHz) for a VSWR<1.5. A four-element array consisting of such elements is shown to provide more than 18° of beam tilt without the need for phase shifters. A method to reduce on-axis cross-polarisation in the circularly polarised array is also presented. In addition, it is shown how the array can be used to produce slant 45° linear polarisation. The resulting array can operate over the personal communication network (PCN) through Universal Mobile Telecommunication System (UMTS) frequency bands, from 1.7 GHz to 2.2 GHz View full abstract»

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  • Synthetic asymptote formula for surface-printed resistor

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    To date, the design of surface-printed resistors has utilised the time-consuming moment method. The synthetic asymptote technique usually generates simple design formulae, and this technique has been extended and applied to the design of surface-printed resistors. It is found that the derived resistance is immune to change even at high frequencies. In addition, it is found that the novel formula for resistance complies with the Pythagorean nature of trigonometry, which forms a simple basis for synthesis and analysis. In comparison with the moment method solution, it is found that the resistance formula has an error of about 3% for all practical slab dimensions. The synthetic asymptote developed allows designers to rapidly determine the resistance View full abstract»

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  • Coupling between microstrip lines embedded in polyimide layers for 3D-MMICs on Si

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    Three-dimensional circuits built on multiple layers of polyimide are required for constructing Si/SiGe monolithic microwave/millimetre-wave integrated circuits on CMOS (low resistivity) Si wafers. However, the closely spaced transmission lines are susceptible to high levels of coupling, which degrade circuit performance. We present finite difference time domain (FDTD) analysis and measured characteristics of novel shielding structures that significantly reduce coupling between embedded microstrip lines. A discussion of the electric and magnetic field distributions for the coupled microstrip lines is presented to provide a physical rationale for the presented results View full abstract»

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  • Wide scanning phased array antenna design in Ka band

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    A millimetre wave active phased array antenna has been developed that is capable of a wide scanning angle in both the E- and H-planes with small deviation in antenna gain. A dipole antenna with parasitic element has been adopted, which may have the capability of adjusting the influence of mutual coupling in the array element pattern. The design of the parasitic element is examined and the effect of its shape on pattern characteristics is confirmed by experiment. Beam scanning angles of ±57.3 degrees in the E-plane and ±68.2 degrees in the H-plane were obtained for each array antenna pattern View full abstract»

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  • Resonant frequencies of post-wall waveguide cavities

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    A new method is presented for predicting the resonant frequencies of post-wall rectangular waveguide cavities, in which the narrow walls of the guide are composed of rows of vias. By interpreting the fields inside the guide as a superposition of plane waves, the surface impedance of a row of wires, when illuminated by a plane wave, is used to model the narrow walls of the waveguide. The derivation leads to equivalent rectangular waveguide dimensions that are then used to calculate the resonant frequencies of the cavity. Theoretical results are compared with the observed TE10m resonant frequencies of several post-wall waveguide cavities fabricated in low temperature cofired ceramic (LTCC). The results confirm that the method improves the resonant frequency prediction when the pitch of the vias is at least ten times greater than their radius View full abstract»

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  • Ring loading of annular sector radiating line antenna

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (381 KB)  

    A modified annular sector radiating line antenna has been designed to improve the efficiency of the basic Anserlin antenna by introducing smooth or serrated annular rings around the antenna. Design curves generated for the modified Anserlin antenna are utilised to produce a four-element series-fed linear array with 18 dB sidelobe taper at 2.1 GHz without the need for an amplitude tapering network View full abstract»

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  • Optimising the computation time of radio coverage predictions for microcellular mobile systems

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (477 KB)  

    The paper presents a method which optimises the computation time of the prediction of radio coverage for microcellular systems, no matter what propagation model is used. The principle consists of reducing the number of application points of the propagation model in relation to the classic technique. The proposed method is based on a multiresolution analysis of measured signals carried out around 2 GHz, and on an electromagnetic analysis of the propagation environment. The performance of the method is evaluated in terms of the reduction in computation time and the effect on accuracy, as compared to the classic technique View full abstract»

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  • Efficient boundary contour mode-matching method of H- and E-plane junctions by fast Fourier transform algorithm

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    An efficient boundary contour mode-matching method (BCMM) is applied to the analysis of H- and E-plane junctions with planar and circular boundaries. The proposed approach is based on the use of the fast Fourier transform (FFT) to improve an analytical BCMM method. The electromagnetic field inside the structure is expressed in terms of circular waves, whereas in the rectangular ports a modal expansion is used. Depending on the shape of the contour, the original field expansion is rewritten in plane waves or in other sets of circular waves, replacing the conventional numerical integrations by a new, more suitable procedure. Finally, the transformation between the different expansions is carried out by means of the FFT, increasing notably the efficiency of the method. The presented formulation is verified by comparing simulated results with those obtained by other numerical techniques View full abstract»

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  • Time domain analysis of circulant symmetric coupled transmission lines

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (401 KB)  

    New coupled transmission lines called circulant symmetric coupled strip lines are introduced. First, the capacitance C and inductance L matrices of the structure are determined using an analytic solution of the Laplace equation. Then, an efficient method (diagonalising the cyclic matrices and modal decomposition of the differential equations) for frequency and time domain analysis of these transmission lines is presented View full abstract»

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