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Microwaves, Antennas and Propagation, IEE Proceedings

Issue 5 • Date Oct 2000

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Displaying Results 1 - 18 of 18
  • Full modal analysis of confocal coaxial elliptical waveguides

    Publication Year: 2000 , Page(s): 374 - 380
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    An efficient method for analysing confocal coaxial elliptical waveguides is presented. Using elliptical coordinates, the differential Helmholtz equation is transformed into a linear matrix eigenvalue problem by means of the method of moments. The expressions of the vector mode functions for the full spectrum of these guides are constructed, including the TEM, TM and TE modes. The convergence of the method is very good, giving an efficient and accurate code. Comparisons with numerical results found in the technical literature validate the presented theory View full abstract»

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  • Dual-band printed antenna for mobile telephone applications

    Publication Year: 2000 , Page(s): 381 - 384
    Cited by:  Papers (5)  |  Patents (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    A compact, lightweight, low-cost, dual-band antenna for GSM and DCS cellular telephone system applications is presented. The antenna, printed on a flexible printed circuit material and shaped round a foam former, is derived from the inverted-F geometry but has a much reduced conductor area. The software design package IE3D was used for design purposes and there was good agreement with measured results. The wide bandwidths required for this application are readily achieved using the antenna geometry. Radiation patterns give omni-directional coverage in the azimuth plane View full abstract»

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  • BPSK and QPSK modulations of an oscillating antenna for transponding applications

    Publication Year: 2000 , Page(s): 335 - 338
    Cited by:  Papers (3)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    An oscillating antenna allowing binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) is demonstrated. The modulating signals are applied to a PIN diode switch and an injection-locked oscillator. Experimental results are presented, including constellation diagrams of the radiated signal and typical waveforms of demodulated signals View full abstract»

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  • Injection-locked coupled microstrip leaky-mode antenna array

    Publication Year: 2000 , Page(s): 364 - 368
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    The paper presents a novel design for an injection-locked microstrip leaky-mode antenna array. It demonstrates that the coupling parameters can be obtained numerically, leading to the analysis of the steady-state phase relationships of the coupled oscillators based on Van der Pol equations for determining the excitation signals of the array. In particular, it applies the coupled-mode approach to investigating the clear and considerable mutual coupling effect on the radiation characteristics of the microstrip leaky-mode array. This, in turn, produces a very efficient and accurate assessment of the radiation far-field patterns. Finally, a proof-of-concept design using a two-element injection-locked microstrip leaky-mode array is presented for experimental verification, showing excellent agreement between theoretical data and measured results View full abstract»

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  • Computing short-term amplitude fluctuations from statistical and spectral characteristics of atmospheric scintillation

    Publication Year: 2000 , Page(s): 325 - 328
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    A model is presented for generating time series to emulate the rapid fluctuations induced by scintillation and affecting waves propagating in the atmosphere. The model time series are generated by taking into account the theoretical power spectral density characteristics of scintillation derived from the theory of propagation in turbulent media. The model also combines the short-term statistical characteristics of scintillation estimated from measurements. A study of the statistics of the scintillation intensity, carried over periods of hours and days, highlights a strong diurnal cycle and is taken into consideration in the model. The first-order statistics of the model time series are compared to measured data and show a good agreement View full abstract»

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  • Electromagnetic levitation of micro-scale actuators using microwave cavity resonators

    Publication Year: 2000 , Page(s): 359 - 363
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    The difficulties of achieving electromagnetic levitation of a small conducting disc, by employing the electric field distribution within the capacitive element of a high frequency resonant system, are discussed. It is shown that as the frequency of the system is raised in order to miniaturise it, the attractive electric levitation force is increasingly counteracted by an oppositely directed Lorentz force. This latter force has to be isolated if effective levitation is to be procured. In `standing-wave' type microwave resonators, the separation of the electric field force and the Lorentz force calls for careful cavity selection and the judicious use of field-selective leakage apertures View full abstract»

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  • Design and measurement of low-cost sector pattern antennas

    Publication Year: 2000 , Page(s): 407 - 411
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    Three sector antennas for cellular communications in the S band, with 60°, 90° and 120° beam widths in the horizontal plane, have been designed, built and measured. A 16-element array has been designed, using a planar multi-layer configuration with patches coupled through slots. The structural configuration, low-cost materials and the same feeding system used in the three antennas make the proposed design very attractive for practical implementation. Measurement results of the three prototypes are presented View full abstract»

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  • Network analysis of inclined microstrip-slotline transitions

    Publication Year: 2000 , Page(s): 412 - 416
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    A general theory for analysing an inclined microstrip-slotline transition is proposed, with a view to developing a network model of the transition. The reciprocity theorem and spectral-domain immittance approach are invoked to formulate the electromagnetic field analysis. The equivalent circuit model consists of an ideal transformer and a series reactance element, and the circuit element parameters are explicitly expressed. The theory is applied to some examples of the transition, including a feed for the tapered-slot antenna, and is shown to yield more accurate results than previous theories View full abstract»

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  • Characteristics of fading and fade countermeasures on a satellite-Earth link operating in an equatorial climate, with reference to broadcast applications

    Publication Year: 2000 , Page(s): 369 - 373
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    Measurements of 12 GHz attenuation, using a satellite beacon receiver, are reported for a station in Malaysia, in one of the most extreme climates with regard to rainfall intensity. The data are analysed, with particular reference to broadcast applications, including data broadcast, multi-media, and time-repeated video applications. Of particular interest is the performance of time diversity, which is characterised with delays between 1 and 60 min. An empirical relationship is proposed, enabling time-diversity gain to be determined as a function of delay. Consideration is given to diurnal variations of attenuation and the additional margin necessary if good performance is to be maintained in peak broadcast hours. The relationship between the annual cumulative statistics of attenuation and the worst month attenuation is also investigated. In such an equatorial climate, with frequent fading throughout the year, it is seen that the worst-month criterion may not be such a useful or necessary measure as in other climates. The problem of prediction of attenuation is addressed using locally collected rain intensity data, and it is seen that further knowledge of rain structure is necessary to improve the quality of predictions View full abstract»

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  • 2D FDTD modelling of objects with curved boundaries, using embedded boundary orthogonal grids

    Publication Year: 2000 , Page(s): 399 - 405
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    An FDTD algorithm was developed using an embedded boundary orthogonal grid system. The algorithm is based on the complex Laplace equation to implement conformal mapping that minimises the magnitudes of the mesh gradients and therefore leads to the smoothest coordinate line distribution over the solution domain. In conjunction with the global rectangular meshes, the local non-orthogonal grids provide versatility of geometry. There is no need to perform interpolation on the boundaries between the local and global grids. As a result, computational time and memory requirements are substantially reduced. The field solution to the unbounded Laplace equation in nonorthogonal coordinates is obtained, and is used as the exciting source to expedite the convergence of the FDTD computations. Numerical examples show good agreement with the results presented in previous publications, both guided wave and scattering problems View full abstract»

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  • Fast spectral domain algorithm for hybrid finite element/boundary integral modelling of doubly periodic structures

    Publication Year: 2000 , Page(s): 329 - 334
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    A fast integral equation algorithm is used for an efficient evaluation of the boundary integral (BI) termination in hybrid finite element (FE)/BI methods, as applied to three-dimensional doubly periodic structures. The method is referred to as a fast spectral domain algorithm (FSDA) since it uses the spectral Green's function representation to evaluate the matrix-vector products carried out within an iterative solver. The FSDA avoids explicit generation of the usual fully populated method of moments matrix. Instead, at each iteration, the actual current distribution is summed up in the spectral domain, and the spectral Floquet mode series (in the evaluation of the BI) is carried out only once per testing function. Thus, the FSDA leads to substantial central processing unit time and memory savings when applied within the FE/BI method for the analysis of infinite periodic structures. This is demonstrated by validation and timing results for a variety of array configurations, which are compared with results obtained using a conventional BI formulation and a BI formulation based on the adaptive integral method. View full abstract»

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  • Couplings of asynchronously tuned coupled microwave resonators

    Publication Year: 2000 , Page(s): 354 - 358
    Cited by:  Papers (28)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    The paper presents a comprehensive treatment of the couplings of asynchronously tuned coupled microwave resonators. The derived formulation allows one to extract coupling coefficients in terms of four characteristic frequencies that can be easily determined numerically or experimentally. To demonstrate the applications, numerical examples are given for asynchronously tuned microstrip coupled open-loop and dual-mode resonators View full abstract»

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  • Full wave edge element based analysis of 3D metal-dielectric structures for high clock rate digital and microwave applications

    Publication Year: 2000 , Page(s): 391 - 397
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    Three-dimensional structures consisting of combinations of metal and dielectric materials are analysed by means of an improved finite-edge element formulation, which incorporates a newly identified term in the standard boundary conditions of the third kind (Cauchy). These conditions take into account both the transverse and longitudinal field components of the propagating signals in the planes of incidence and transmittance. Employing these boundary conditions, in conjunction with the absorbing boundary conditions (ABC) and/or the boundary conditions of the first kind (Dirichlet) and the third kind, a 3D asymmetrical functional is implemented as a hybrid vector edge element method. Numerical examples are presented for air bridges and lossy transmission lines, connected by a through-hole via and a spiral inductor. The equivalent frequency dependent circuit parameters are then extracted from the field solutions. Laboratory measurements and data comparison with previous published results strongly support the newly developed theoretical work View full abstract»

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  • Fast spectral domain algorithm for hybrid finite element/boundary integral modelling of doubly periodic structures

    Publication Year: 2000 , Page(s): 329 - 334
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    A fast integral equation algorithm is used for an efficient evaluation of the boundary integral (BI) termination in hybrid finite element (FE)/BI methods, as applied to three-dimensional doubly periodic structures. The method is referred to as a fast spectral domain algorithm (FSDA) since it uses the spectral Green's function representation to evaluate the matrix-vector products carried out within an iterative solver. The FSDA avoids explicit generation of the usual fully populated method of moments matrix. Instead, at each iteration, the actual current distribution is summed up in the spectral domain, and the spectral Floquet mode series (in the evaluation of the BI) is carried out only once per testing function. Thus, the FSDA leads to substantial central processing unit time and memory savings when applied within the FE/BI method for the analysis of infinite periodic structures. This is demonstrated by validation and timing results for a variety of array configurations, which are compared with results obtained using a conventional BI formulation and a BI formulation based on the adaptive integral method View full abstract»

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  • Method of moments analysis of a waveguide crossed slot by using the eigenmode basis functions derived by the edge-based finite-element method

    Publication Year: 2000 , Page(s): 349 - 353
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (408 KB)  

    A hybrid analysis of the method of moments (MoM) and the finite-element method (FEM) is proposed for a waveguide crossed slot. The eigenmode functions of an X-shaped waveguide, with the geometry of a crossed slot in the cross section, are utilised as the basis functions of the magnetic currents in the MoM. They are derived as vectors by the edge-based FEM to express the current flow accurately around the crossing part. Reactions in the wall-thickness region of the rectangular waveguide can be simply and accurately evaluated without taking mode summation because of the orthogonality of the eigenmodes. The proposed method is advantageous for a crossed slot, especially with a wide slot width and a thick waveguide wall. For the verification of the analysis, the calculated results of the transmission coefficient, and the radiation pattern are compared with the measured ones using a 12 GHz model antenna. The agreement in the transmission coefficient is very good both in amplitude and phase from 10 to 15 GHz View full abstract»

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  • Behaviour of the parallel plate mode in a stripline slot-coupled patch antenna

    Publication Year: 2000 , Page(s): 385 - 389
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (352 KB)  

    Excitation of the parallel plate mode is a serious concern in a stripline slot-coupled patch antenna, and the paper is a study of its behaviour. The frequency dependence of the parallel plate mode power ratio to the input power of the antenna is discussed by means of an equivalent circuit of the antenna. It is found that the parallel plate mode power ratio is very small when the antenna is operated at the resonant frequency of the patch. A prototype antenna (in which impedance matching is obtained at the resonant frequency of the patch) is designed and fabricated. Measurement of the parallel plate mode power is performed to confirm the validity of the considerations. It is concluded that the antenna should be operated at the resonant frequency of the patch to minimise the unwanted effect concerning the parallel plate mode View full abstract»

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  • Effect of finite ground-plane widths on quasistatic parameters of asymmetrical coplanar waveguides

    Publication Year: 2000 , Page(s): 343 - 347
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    CAD-oriented closed-form expressions are presented for calculating the quasistatic TEM parameters of asymmetrical coplanar waveguides (ACPWs) with finite ground planes. The effect of the ground-plane width on the quasistatic parameters has been investigated by using the formulas derived by the conformal mapping techniques. Comparisons have also been made between the present results and the results available in the literature for both the conventional coplanar waveguide (CPW) and ACPW. The results are in good agreement with the results derived by the conformal mapping technique and the spectral-domain method. It has been shown that the present expressions can also be used for calculating the quasistatic parameters of both symmetric and asymmetric CPWs with finite and infinite ground planes View full abstract»

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  • Spectral domain approach to 2D-modelling of open planar structures with thick lossy conductors

    Publication Year: 2000 , Page(s): 321 - 324
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    Real planar structures, in contrast to ideal ones, involve lossy conductors of finite thickness even when neglecting dielectric losses: these characteristics play a fundamental role in MMIC interconnecting lines. A full-wave approach to the modelling of their dispersion characteristics is introduced, suitable for open structures. The method is a continuous spectral domain formulation of the generalised transverse resonance-diffraction (G-TRD). As the standard G-TRD, its open counterpart could also be used to model linear active devices View full abstract»

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