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Microwaves, Antennas and Propagation, IEE Proceedings

Issue 4 • Date 5 Aug. 2005

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Displaying Results 1 - 14 of 14
  • Spatial shape demagnetising factors of disc, equilateral triangle and irregular hexagonal magnetic insulators

    Publication Year: 2005 , Page(s): 201 - 208
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1097 KB)  

    The connection between the external and internal direct magnetic field intensities in an ellipsoidal magnetic insulator in a uniform field is a classic result in the literature. It is usually stated in terms of shape demagnetising factors. The case of the non-ellipsoidal geometry in a uniform field has been dealt with in a number of approximate ways but has by and large been restricted to disc geometries in infinite space. The aim of the paper is to verify some existing relationships on the spatial dependent shape demagnetising factors of the classic disc insulator by having recourse to a static magnetic solver. The demagnetising factors along the two main coordinates of equilateral and irregular hexagonal magnetic insulators are also evaluated. View full abstract»

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  • Simplified graphical analysis of linear three-port stability

    Publication Year: 2005 , Page(s): 209 - 213
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1374 KB)  

    The paper presents a simplified graphical analysis of linear three-port stability. Instead of the previously reported three conditions, only one plot of a single stability condition needs to be constructed in each termination reflection plane. The plot is useful to aptly depict the terminations at each port that result in unconditional stability between the remaining two ports. Such unconditional stability is ascertained using the single necessary and sufficient condition, which is expressed in a generalised form in terms of three-port S-parameters. The construction of three-port stability plots is delineated and exemplified to illustrate the convenience using the single condition. These stability plots find direct application in the stabilisation of potentially unstable networks. View full abstract»

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  • Simple and improved dielectric parameter extraction of thin organic packaging materials using open-ended coaxial line technique

    Publication Year: 2005 , Page(s): 214 - 220
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (279 KB)  

    A low cost model utilising foam as an optimum sample backing has been used to measure the complex permittivity of thin packaging substrates over a broadband frequency of 0.1-20 GHz. Based on the open-ended coaxial line technique, the model validity has been verified both theoretically and experimentally, and a good accuracy is achieved. In addition, the model provides convenient probe calibration, thus enabling a fast extraction of the dielectric parameters utilising one port measurements. In particular, good agreement between the measured results and the manufacturer's data has been obtained, along with stable values of the material dielectric parameters over wide band frequencies. A good correlation has also been obtained between the measurement and simulation results over broadband. View full abstract»

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  • Dielectric loaded slot in a parallel-plate waveguide coupled to a conducting cylinder

    Publication Year: 2005 , Page(s): 221 - 225
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (182 KB)  

    A simple numerical solution is given for the problem of a parallel-plate waveguide with a slot covered by a dielectric semi-cylinder of arbitrary cross-section. The exterior half-space of the waveguide contains also a perfectly electrically conducting (PEC) cylinder, which is disjoint from the dielectric cover. The excitation is an incident TEM wave from within the waveguide. The surface equivalence principle is used to obtain a set of coupled integral equations in terms of the aperture electric field, and the equivalent electric currents on the PEC and the dielectric cylinder. The integral equations are solved numerically by the method of moments. For several practical cases, the effects of conductor and dielectric loading on the reflection coefficient and radiation pattern data are presented along with the aperture electric field and cylinder currents. View full abstract»

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  • Simplified analysis for the initial design of rectangular waveguide cross-slot couplers

    Publication Year: 2005 , Page(s): 226 - 230
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (231 KB)  

    For the purpose of providing initial designs of waveguide cross-slot couplers, the authors present a simplified analysis of cross-slot coupling through the common broad wall of two rectangular waveguides. Straightforwardly implementable equations are presented which not only include a wide range of cross-slot dimensions but also the location as well as the rotation of the cross-slot in a coupler environment. Moreover, asymmetric coupler structures can be easily incorporated. Analyses of individual structures are verified by HFSS. Two examples of cross-slot waveguide couplers demonstrate the applicability of this technique for the initial design of waveguide cross-slot couplers. View full abstract»

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  • Even and odd mode cut-off parameters of pairs of ridges in rectangular waveguide using a mode matching solver

    Publication Year: 2005 , Page(s): 231 - 237
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (437 KB)  

    A waveguide geometry of some interest consists of a symmetrical pair of ridges in a rectangular waveguide. The paper gives the even and odd mode cut-off spaces of such a structure in addition to its corresponding standing wave patterns. The classic power-voltage, power-current and voltage-current definitions of impedance of the two solutions are also evaluated. The calculations are based on a mode matching procedure and are verified separately using a finite element solver. A knowledge of these parameters is sufficient for the design of a proximity, reverse, directional coupler. View full abstract»

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  • Interaction of a semiconductor sample partly filling a waveguide's window with millimetre wave radiation

    Publication Year: 2005 , Page(s): 240 - 244
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (447 KB)  

    Interaction of a semiconductor sample with an electromagnetic wave within the millimetre range has been investigated. A three-dimensional finite-difference time-domain method was applied to simulate wave propagation within a waveguide segment with the semiconductor sample attached to a wide wall of the waveguide. The electric field distribution, voltage standing-wave ratio and the average electric field dependencies in the 78-118 GHz frequency range have been determined for several sets of dimensions and specific resistances of the sample. These investigations have been the basis for the design of the resistive sensor (RS) based on the electron heating effect and devoted to high-power millimetre-wave pulse measurement. By choosing the dimensions and specific resistance of the sample, the decrease in the electron heating effect with frequency as well as the decrease of electric field in the waveguide due to wave dispersion were compensated by an increase in the average electric field. Therefore an RS having practically unchanging sensitivity in a waveguide's frequency range has been proposed. View full abstract»

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  • Modified dual-mode double-ring resonators for wide band-pass filter design

    Publication Year: 2005 , Page(s): 245 - 250
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (395 KB)  

    A novel design of a dual-mode resonator with modified double rings structure for a wide band-pass filter is presented. Based on the mode chart and double rings resonator, modified double rings comprising three half rings are proposed. In addition each ring exhibits dual-mode responses, those rings determine the whole operating band; i.e. the smaller/larger rings depict the upper/lower frequencies of the pass-band and construct the flat of response for wideband applications. This is an alternative approach to achieve performance of low insertion loss, wide pass-band and sharp rejection band. Experimental and simulation results are presented and discussed. View full abstract»

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  • Periodically loaded dipole array supporting left-handed propagation

    Publication Year: 2005 , Page(s): 251 - 254
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (865 KB)  

    Periodically loaded dipole arrays printed on grounded dielectric substrate are shown to exhibit left-handed propagation properties. In an equivalent transmission line representation, left-handedness emerges due to the excess series capacitance and shunt inductance. Based on this concept, the authors study the distribution of the modal fields and the variation of series capacitance and shunt inductance as the dipoles are loaded with stubs. Full wave dispersion curves that show the gradual transition from a right-handed to a left-handed medium upon periodically loading the dipoles with stubs are presented. An equivalent circuit is derived that matches to a very good extent the full wave result. The cell dimensions are a small fraction of the wavelength (λ/5), so the structure can be considered as an equivalent homogeneous surface. The structure is simple, readily scalable to higher frequencies and compatible with low-cost fabrication techniques. View full abstract»

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  • Modified PIFA and its array for MIMO terminals

    Publication Year: 2005 , Page(s): 255 - 259
    Cited by:  Papers (19)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    A study on a modified planar inverted-F antenna (PIFA), operating at 5.2 GHz within the IEEE802.11a WLAN frequency band (5.15-5.35 GHz) with a very small ground plane (7 mm×12 mm) and its application to multiple input multiple output (MIMO) systems is presented. While it inherits the attractive features of PIFAs, such as compact size and low profile, the modified antenna exhibits low coupling to the printed circuit board (PCB). A 2-element PIFA array is implemented on a mobile handset PCB and an isolation better than 28 dB is achieved in both simulation and measurement. View full abstract»

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  • Fast array analysis using a combination of FDTD and matrix manipulation techniques

    Publication Year: 2005 , Page(s): 260 - 266
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (929 KB)  

    In many cases, antenna array design and modelling are performed by the finite difference time domain (FDTD) method. The method is robust but very demanding in computer memory and CPU power. The authors present a new method that allows otherwise impractical FDTD simulations to produce valid results with no great dissipation of computer power. This is achieved with a combined effort of reduced full-wave simulations and matrix manipulations in the proposed array geometry. With the new scheme, the computational limitations of the conventional FDTD analysis are surpassed and the scope of the analysis itself is broadened; changes in electrical characteristics of an array, such as beam scanning, do not necessitate new simulation runs. View full abstract»

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  • Dual frequency circularly polarised microstrip antenna

    Publication Year: 2005 , Page(s): 267 - 272
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (772 KB)  

    A dual frequency and dual circular polarisation multilayer microstrip antenna element for satellite communication is presented. The element is fed by a gap-coupled probe pin. The microstrip element exhibits a dual frequency band of operation for two orthogonal circular polarisations. A parametric study to optimise the element performance has been conducted. A prototype with dimensions that are based on the simulations has been built and tested. A good agreement between the measured and numerical results was found. View full abstract»

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  • Design of a CPW-fed notched planar monopole antenna for multiband operations using a genetic algorithm

    Publication Year: 2005 , Page(s): 273 - 277
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    A CPW-fed notched planar monopole antenna is designed for multiband operations using a genetic algorithm (GA) in conjunction with the method of moments (MoM). By introducing a suitable notch to a rectangular CPW-fed patch, the desired multi-frequency resonant modes and broad impedance bandwidths can be obtained. The use of a GA enabled the dimensions of the CPW-fed notched patch structure to be changed at will as optimum impedance matching at the selected bands was sought. Prototypes of the proposed GA-optimised design were constructed and studied experimentally. The measured results of the resulting antenna not only explore good multiband operations with 10 dB impedance bandwidths of 15.3%, 16.6% and 18% at the design bands of 2.42, 3.61 and 5.28 GHz, respectively, but also show good agreement with the numerical prediction. Additionally, details of the physical GA implementation for the optimised configuration are presented and discussed. View full abstract»

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  • Statistical modelling at 20GHz for fixed wireless access systems in urban multipath environments

    Publication Year: 2005 , Page(s): 278 - 283
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

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