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Microwaves, Antennas and Propagation, IEE Proceedings

Issue 1 • Date 6 Feb. 2006

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Displaying Results 1 - 17 of 17
  • High-gain subwavelength resonant cavity antennas based on metamaterial ground planes

    Page(s): 1 - 6
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1005 KB)  

    Planar metamaterial surfaces with negative reflection phase values are proposed as ground planes in a high-gain resonant cavity antenna configuration. The antenna is formed by the metamaterial ground plane (MGP) and a superimposed metallodielectric electromagnetic band gap (MEBG) array that acts as a partially reflective surface (PRS). A single dipole positioned between the PRS and the ground is utilised as the excitation. Ray analysis is employed to describe the functioning of the antennas and to qualitatively predict the effect of the MGP on the antenna performance. By employing MGPs with negative reflection phase values, the planar antenna profile is reduced to subwavelength values (less than λ/6) whilst maintaining high directivity. Full-wave simulations have been carried out with commercially available software (Microstripes™). The effect of the finite PRS size on the antenna radiation performance (directivity and sidelobe level) is studied. A prototype has been fabricated and tested experimentally in order to validate the predictions. View full abstract»

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  • Self-balanced wideband folded loop antenna

    Page(s): 7 - 12
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (422 KB)  

    A folded loop antenna for handsets has already been introduced and shown as one of the balance-feed antennas for handsets, which is very effective at mitigating the antenna performance degradation owing to body effects. In order to meet the requirements for the latest handsets such as small size and wideband characteristics, a folded loop antenna is modified to have wider band characteristics. A folded loop antenna has a self-balanced structure so that the current on the ground plane (GP) can be reduced even though an antenna is fed by an unbalanced line such as coaxial cable. The antenna, which is introduced here, is also expected to maintain this effect. In the analysis, the electromagnetic simulator based on the method of moments (MoM) is used. Also design parameters, which are useful in practical operation, are found. An example of a wideband antenna, which has a self-balanced effect, is designed based on these parameters. In addition, antenna characteristics such as VSWR, the current distributions and the radiation patterns are shown. As a result, it has been confirmed that the antenna has wideband characteristics and a self-balanced effect. View full abstract»

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  • Beam adaptive single arm rectangular spiral antenna with switches

    Page(s): 13 - 18
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    A rectangular spiral antenna with switches is proposed for beam adaptive applications. The excitation of switches introduces variations in the current distribution on the antenna arm, thus causing the beam to steer. A switch is implemented as an element to short-circuit at a point on the spiral arm to the ground conductor (shorted spiral antenna). A shorted spiral configuration using four switches is analysed. For this configuration, both single- and multipoint switching are implemented. Sixteen possible switching cases are investigated. The radiation patterns are measured in the Satimo antenna test facility and numerically supported using the finite-difference time-domain (FDTD) method. Tilted (24°<θmax<44°) and axial (5°<θmax<12°) beams are obtained using various switching cases, thus realising an adaptive antenna. The gain, which is approximately 6.5 dBi, stays uniform within ±1 dB variation and the VSWR remains within an acceptable limit of 2 for the majority of the switching cases. View full abstract»

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  • Planar radiator with refined slot pattern for electrically small antennas

    Page(s): 19 - 24
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2925 KB)  

    The authors present a novel radiator as a basic element of electrically small planar antennas for various short-range wireless applications. The proposed radiator takes advantage of its unique topology in order to improve a bandwidth of otherwise narrow-band conventional antennas. The radiator comprises a thin metal layer preferably formed on a surface of the dielectric substrate, and a slot pattern within that layer configured with four convoluted slot arms terminating a main slot at each end. One pair of terminating slot arms is convoluted clockwise while another pair is convoluted counterclockwise. The combination of clockwise and counterclockwise convoluted slot arms provides the termination with unique electromagnetic features. The slot arms are further formed as mirror-symmetrical couples with respect to the main slot line. The rigorous theoretical analysis is validated by precise prototyping and accurate experiments with UHF microstrip fed antennas. The bandwidth of the antenna with the proposed radiator becomes at least 30% wider without any affect on radiation pattern, gain, and polarisation purity. It is shown that improvement in the bandwidth has been achieved exclusively owing to the refined slot pattern. View full abstract»

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  • High-efficiency class-B push-pull amplifying array for microwave transmitting front end

    Page(s): 25 - 28
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    The authors present a novel push-pull amplifying array using quadruple antenna-patch couplers and dual-feed antennas. It exploits the advantages of both class-B push-pull amplifiers and active integrated antennas (AIAs), resulting in a high-efficiency, linear and yet compact design. A state-of-the-art heterojunction FET power amplifier of 50% peak power-added efficiency (PAE) is achieved at 10 GHz. A three-element array prototype was successfully built, achieving a peak antenna gain of 19.6 dBi. This is 5.7 and 10.4 dB better than amplifying arrays using the antenna-patch coupler approach and the conventional parallel feeding network, respectively. View full abstract»

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  • Moment method analysis of circular cylindrical array of waveguide elements covered with a multilayer radome

    Page(s): 29 - 37
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (781 KB)  

    An analysis of an array of rectangular waveguide openings in a circular cylindrical groundplane covered with a radome is presented. The analysis method is based on the modal solution, i.e. on the superposition of one-dimensional spectral solutions, and on the method of moments. The modal approach requires the summation of a large number of terms in the Fourier series for structures with large radii. Furthermore, highly oscillating integrals occur when the waveguide openings are axially separated. Both problems are treated with special care: asymptotic formulas are used for calculating the Green's functions, and the integration contour for calculating the inverse Fourier transformation is carefully selected. Measurements on an 18×3 waveguide array on a circular cylindrical structure covered with a radome have been used for verification of the theoretical results. The effect of an airgap between the waveguide openings and the radome is discussed. The agreement between calculated and measured values of mutual coupling, input admittance and radiation patterns is very good. View full abstract»

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  • Design of a radial waveguide feed network for a pin-fed array antenna

    Page(s): 38 - 42
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (703 KB)  

    An efficient design procedure for a radial waveguide feed network for an array antenna, whose radiating elements are pin-fed, is presented. A model of the feed network is considered and relevant design parameters are expressed by simple analytic terms. To facilitate the design of the feed, a useful coupling chart for a pin-loaded radial waveguide is suggested. It shows graphically the dependence of the coupling coefficients between the radially outward-travelling wave and the feeding pins on the length of their protrusion inside the waveguide. To render the model more realistic, the mutual coupling occurring between the pins within the waveguide is not neglected. Instead, it is taken into account by use of the known expressions for the mutual resistance and reactance between two equal-length and side-by-side parallel monopoles. Results are verified by experimental data available in the literature. View full abstract»

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  • Modelling and design of a finite dual-polarised notch phased-array antenna

    Page(s): 43 - 48
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1067 KB)  

    The authors present the modelling and design procedure for a finite dual-polarised notch phased-array antenna which has a triangular lattice to obtain a widescan ability in the azimuth and elevation planes. The array antenna has orthogonal linear polarisations for transmitting and receiving, and the triangular element grid is achieved by 45° rotation of a square grid of notch elements in egg-crate configuration. A numerical waveguide simulator for the H-plane scan is modelled to eliminate scan blindness in the H-plane. A numerical model for the finite dual-polarised notch array is built to investigate the convergence of the active-element pattern (AEP) and the effects of the grating lobe according to array size. To verify the numerical results, a wideband active phased-array system was fabricated which consists of a 10×12×2 notch array, 8×8 transmit/receive modules and beam-forming networks. The scan patterns measured by near-field measurement show good agreement with the converged AEP for the finite array model and have widescan performance in the azimuth and elevation planes. View full abstract»

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  • Development of dual-band circularly polarised reflectarray

    Page(s): 49 - 54
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    The development of a dual-band circularly polarised microstrip reflectarray in Ka-band is presented and various reflectarray configurations with different cell elements are introduced. Among these, reflectarrays with separate crossed dipoles or orthogonal nonintersecting dipoles etched on the same or different substrate interfaces were investigated theoretically and experimentally. Adjusting the lengths of the orthogonal dipoles or arms of the cross dipoles was used to maintain 90° relative phase shift between the orthogonal components of reradiated fields and this gives rise to the realisation of a reflectarray that converts the linearly polarised incident field of the feed into an outgoing circularly polarised field. Various realisations of reflectarrays in terms of cell elements and configuration were designed, fabricated and tested. Measurement results for the final prototype that was of superior performance compared to the other prototypes demonstrated 36% aperture efficiency and axial ratio better than 2.0 dB, for 3% bandwidth on both the Tx and Rx bands. View full abstract»

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  • Multidomain pseudospectral time-domain algorithm based on super-time-stepping method

    Page(s): 55 - 60
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (273 KB)  

    A new time-domain algorithm which combines the super-time-stepping (STS) method and the multidomain pseudospectral time-domain (PSTD) algorithm is presented. This algorithm not only maintains accuracy and flexibility of PSTD for an accurate treatment of arbitrarily curved objects but also relaxes the stability restriction for the explicit time integration scheme, establishing it for possible use in any implicit time integration scheme. Some numerical examples are given to illustrate the accuracy and efficiency of this proposed approach. View full abstract»

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  • Innovative basis and weight functions for wire junctions in time domain moment method

    Page(s): 61 - 66
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (329 KB)  

    A wireframe implementation of the method of moments in time domain is presented, with particular attention to wire junctions. Peculiar base and weight functions will be defined at the junctions to implicitly account for current continuity and correctly take into account inter-wire coupling. This will allow implementation of both an explicit and an implicit solution. Results obtained are validated with existing frequency domain solutions. View full abstract»

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  • Accuracy evaluation analysis for indoor measurement-based radio-wave-propagation predictions

    Page(s): 67 - 74
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1939 KB)  

    An accuracy evaluation analysis of in-building path loss prediction models is presented, comparing the performance of measurement-based prediction against traditional indoor radio propagation models, such as Keenan-Motley, tuned with measurements. The analysis was conducted using extensive walk test data from various antennas at 1800 MHz collected in two types of buildings: an old Victorian manor-house built from brick and a modern purpose-built office building with open-plan construction. The measured data were split into two parts: a tuning set and an evaluation set, such that the data used to run the measurement-based prediction were excluded from the data used for the accuracy evaluation analysis. The results show a significant improvement in the prediction accuracy for the indoor measurement-based model over the tuned Keenan-Motley model. View full abstract»

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  • Multimode degenerate mode cavity for microwave hyperthermia treatment

    Page(s): 75 - 82
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (613 KB)  

    The paper describes a new approach to the selective transmission of electromagnetic energy into a well-defined volume of a dielectric medium, to produce very localised heating within the medium. The concept is based on mode degeneracy in high-order-mode microwave cavities, and constructive field enhancement when several carefully selected degenerate modes are excited simultaneously. A particular embodiment of the cavity system might be a noninvasive hyperthermia procedure designed to raise the temperature of isolated, well-defined, tumours in a human patient or an animal, to eradicate cancer cells in a defined location. Theoretical results based on constructive interference processes for selected modes, which find their basis in well-established antenna-array pattern formulations, are presented. View full abstract»

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  • Modelling and application of elastomer mesh for microwave probing

    Page(s): 83 - 88
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2047 KB)  

    A novel microwave probing application using elastomer mesh is described. It is targeted for testing wafer level packages with very fine pitch of the order of 100 micron and large pin counts of the order of a thousand. The metallised elastomer mesh provides mechanical compliance as well as good electrical contact. A mesh-coplanar probe is modelled by the partial element equivalent circuit (PEEC) method. The model is verified through frequency domain measurements on a prototype test fixture. View full abstract»

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  • Investigation of new nondegenerate dual-mode microstrip patch filter

    Page(s): 89 - 95
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (906 KB)  

    A new nondegenerate dual-mode microstrip patch filter structure is introduced. The proposed filter is based on a square microstrip patch with four slots etched in symmetrical form. Besides its simple structure, the filter has the advantages of small size and low loss. The full-wave IE3D package is used to analyse the proposed structure. Design curves that relate the mode resonance frequencies and fractional bandwidth against slot parameters are presented. A bandpass filter is designed, analysed and tested at 2.15 GHz. Experimental results show good agreement with theoretical results. View full abstract»

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  • Noise characteristics of an oscillator with a barium strontium titanate (BST) varactor

    Page(s): 96 - 102
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (290 KB)  

    The phase noise of an oscillator with a thin-film barium strontium titanate (BST) capacitive tuning element, or varactor, is characterised and benchmarked against the same oscillator with a silicon semiconductor junction varactor. Phase noise tracks closely with varactor Q within a specific voltage range as expected. Compared to the semiconductor varactor-based oscillator, the BST-based oscillator demonstrates reduced phase noise degradation near zero volts, but greater phase noise degradation when operated near breakdown. View full abstract»

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  • Radar cross-section analysis for passive RFID systems

    Page(s): 103 - 109
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    The authors analyse radar cross-section (RCS) for operational optimisation of radio frequency identification (RFID) systems. The research work is based on both theoretical analysis and scattering pattern measurements over tag antennas with four different loads. Furthermore, the influence of the tags' antenna ground plane size to their performance is analysed. Theoretically, short circuited tags scatter all the incoming field to their environment, while a perfectly matched antenna does not scatter at all. Furthermore, the antenna shape has a significant role in the total scattered RCS, while antenna mode RCS is under 1 m2 for both measured antennas. In addition, as the dimension of the antenna's ground plane is increased, the maximum identification range with reliable identification is not increased; instead, only the maximum achievable identification range increases. The results presented are useful when optimising tag performance, and further identification range. View full abstract»

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