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IEEE Transactions on Antennas and Propagation 01/2013; 61(1):100-108. · 2.15 Impact Factor
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IET Microwaves Antennas & Propagation 01/2012; 6(11):1207-1214. · 0.68 Impact Factor
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IEEE Transactions on Antennas and Propagation 01/2012; 60(4):2028-2035. · 2.15 Impact Factor
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18th IEEE International Conference on Electronics, Circuits and Systems, ICECS 2011, Beirut, Lebanon, December 11-14, 2011; 01/2011
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ABSTRACT: A four-sided folded, slotted and shorted rectangular patch antenna for 3G mobile handsets is described. The antenna provides a 17.65% bandwidth with S11 <−10 dB from 1885 MHz to 2250 MHz, which completely encompasses the desired UMTS frequency band (1920–2170 MHz). The proposed antenna is minimized to a volume of 30 mm × 30 mm × 10 mm, in which the side length dimension is ∼0.2 wavelengths at the centre frequency 2045 MHz, whilst the height of the antenna above ground plane is about 1/15 wavelength. The experimental and simulated results on a finite ground plane show good agreement. The effect of varying key geometrical parameters of the proposed antenna is also discussed. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1549–1553, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25271
Microwave and Optical Technology Letters 04/2010; 52(7):1549 - 1553. · 0.62 Impact Factor
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ABSTRACT: A novel quadrifilar spiral antenna is proposed for use in personal communications mobile terminals exploiting the “big low earth orbit” (big-LEO) satellite system (uplink 1.61–1.63 GHz; downlink 2.48–2.5 GHz). Feeding of the antenna from the outer periphery is proposed, to avoid the complexity and space requirements of a centre feed; an externally fed antenna can also be fed either by coaxial cables or stripline. Moreover, the hybrid phasing network and the matching network (if required) can be located outside and possibly printed in the same plane as the antenna structure. Versions of the design were investigated using the method of moments and in hardware realizations. These had a finite ground plane with air dielectric between the spirals and the ground plane. Performance suitable for satellite mobile system applications was demonstrated, including dual-band matching. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:987–990, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25090
Microwave and Optical Technology Letters 03/2010; 52(4):987 - 990. · 0.62 Impact Factor
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ABSTRACT: Size constraints and mutual coupling on the performance of a two-antenna assembly are investigated. Planar inverted F antenna structures are used, and the design frequency is 2.4 GHz. A benchmark antenna assembly, employing a normal metallic ground plane is compared with an EBG modified ground plane. The height of the antenna elements over the EBG is optimised, and an isolation factor of 9.12 dB is achieved for a gap of 2.5 mm. Prototype structures have been constructed and measured for both cases. I. INTRODUCTION This paper investigates the mutual coupling experienced in a two-antenna module operated at 2.4 GHz, the antenna elements are planar inverted F structures (PIFA), and the investigation takes into account the possibility of replacing a conventional metal ground plane with a modified EBG structure [1]. The size and performance requirements found in many mobile user terminals, handsets, and vehicular applications lead naturally to the use of printed dipoles, and similar structures, operated against a metallic ground. In addition to this background it is also necessary to consider the current evolution towards realistic MIMO user terminal applications, eventually miniaturised multi-antenna modules may become routine requirements. PIFA structures have been selected for this study because of their electrical performance, and compact design features. However, there several physical constraints which apply in attempting miniaturisation of such antennas, particularly with respect to reductions in substrate thickness. If this process is applied, the gross size reductions are achieved at the cost of poor radiation performance, and mutual coupling within the terminal radiator elements, and to the user. Several attempts have been made to mitigate this situation through the selective application of metamaterials [2-5]. Conventional PIFA designs are reviewed in [6-10]. A design making use of metamaterial loaded walls, suing a Sievenpiper (i.e. 'mushroom') structure is given in [11].
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ABSTRACT: A new uniplanar compact electromagnetic bandgap (UC-EBG) structure is proposed in order to achieve a smaller unit cell operating at lower frequency stop band. Its design is detailed and an experimental result is presented. The property of the proposed UC-EBG is compared with the distorted uniplanar compact EBG (DUC-EBG). The application of the proposed UC-EBG is examined. A parametric study on various thicknesses of dielectric substrate is also discussed.
Antennas & Propagation Conference, 2009. LAPC 2009. Loughborough; 12/2009
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ABSTRACT: A circularly polarized quadrifilar helical antenna, operated at 2.4 GHz and intended for applications in satellite mobile communications, is designed using genetic algorithms (GA). The antenna was firstly considered as a test on an infinite ground plane and then optimized further on small size handsets. The performance of the optimized antenna design was analyzed using commercial simulators in terms of impedance match, axial ratio, and gain. Results for the optimal antenna met the design objectives subject to certain parametric constraints. The design shows the capabilities of GA as an efficient optimization tool for selecting globally optimal parameters to be used in simulations with an electromagnetic antenna design code, seeking convergence to specific design specifications. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2668–2671, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24694
Microwave and Optical Technology Letters 08/2009; 51(11):2668 - 2671. · 0.62 Impact Factor
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ABSTRACT: In recent years, electromagnetic dosimetry has been increasingly oriented towards the evaluation of energy deposition in the human body due to an exposure to cellular telephones. In this case of near-field exposure, the significant dosimetric parameters are the specific absorption rate (SAR). This kind of definition causes a technical problem, because the SAR inside a person cannot be measured. Therefore, some indirect way is needed to establish the compliance of a certain device with the basic restrictions. This paper therefore mainly deals with SAR measurement for phased antenna array including some antenna prototypes. Some of these measurements on one other form of the array (using helices) have been only optimised empirically. The measurements use the dosimetric techniques already developed for the compliance testing of mobile telephones. The experimental approach is then described, based on invasive SAR measurements by means of miniaturised E-field probes inside a control phantom. The relative measured SAR values between the uses of phased antenna array to the conventional single antenna handset are presented.
Antennas and Propagation, 2009. EuCAP 2009. 3rd European Conference on; 04/2009
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ABSTRACT: A circularly-polarized conical-beam microstrip patch antenna, with a coplanar conductor pattern, is realized as an array of a number of stripline-fed slotted patches whose diagonal corners are cut off and whose feedlines meet at a central point. Prototypes of such an antenna array with four patches are studied and tested. The results show reasonable agreement between measured and theoretical results. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 78–81, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23956
Microwave and Optical Technology Letters 12/2008; 51(1):78 - 81. · 0.62 Impact Factor
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ABSTRACT: A novel internal triple-band folded planar antenna for mobile handsets is introduced, formed by modifying the geometry of a rectangular patch antenna to include a shorting pin, folded sides, a shorted microstrip stub and a notch. The size of the antenna is successfully reduced to a volume of 34 times 34 times 7 times mm<sup>3</sup>. The antenna is mounted on a finite ground plane of 50times100 times mm<sup>2</sup>. The impedance bandwidth achieved was 29.7% (equivalent to return loss%%10%dB); this covers the DCS1800, PCS1900 and UMTS 2000 bands. The characteristics of the proposed antenna, including impedance bandwidth and far field radiation patterns are discussed theoretically and experimentally; the simulated and measured results show good agreement. The tuning effects of the geometry parameters on impedance matching of the proposed antenna are also investigated.
IET Microwaves Antennas & Propagation 11/2008; · 0.68 Impact Factor
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ABSTRACT: Fano integrals are assessed as objective measures of antenna bandwidth and bandwidth improvement schemes. Comparing a U-slot dual resonant antenna with a singly resonant form suggests the integral is invariantly related to overall volume.
Antennas and Propagation, 2007. EuCAP 2007. The Second European Conference on; 12/2007
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ABSTRACT: Impedance and admittance functions of simple bicone and bowtie dipole antennas are modelled using rational functions of low order. Results are presented in terms of the poles and residues of the function, which are studied as functions of the flare angle. Excellent agreement can be obtained between electromagnetic models and the analytic function to low order. Addition of a ground plane is found to produce the expected doubling of the poles at non zero frequencies. For a specimen bowtie, the Q-factor of the first admittance and first impedance pole is rather higher in the flared form than in the thin form. This appears to counter the increase in DC capacitance to give little change in bandwidth.
Antennas and Propagation Conference, 2007. LAPC 2007. Loughborough; 05/2007
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ABSTRACT: A formula is derived for the effective bistatic radar cross-section of a rain cell with Gaussian reflectivity profile assuming antennas with Gaussian radiation patterns. The size and location of the rain cell are arbitrary, as is the bistatic scattering geometry. The expression is analytical, avoiding the need for numerical integration, and general, allowing treatment of cases with only partial beam intersection. Using a recently proposed model, sidelobe contributions and multiple cells embedded within widespread rain debris can be incorporated.
International Journal of Satellite Communications 03/2007; 11(3):163 - 168.
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ABSTRACT: The application of propagation theory to the structure and control of adaptive networks designed to cancel hydrometeor-induced cross-polarization in microwave communication links is summarized. When adaptive cross-coupling networks are realized at radio frequency as variable waveguide polarizers, desirable simplifications are to make them lossless devices with at most two free parameters. Performance calculations for such simplified forms are fully reviewed.Several new approaches to the design of controllers for the cancelling networks are also made possible. New results are presented on the performance of systems which use only one pilot tone, or even dispense with cross-polar measurement completely. It is also shown that the reciprocity of the hydrometeor medium, an apparently safe assumption, makes possible an extract precorrection of a transmitted polarization if control is based on a beacon signal of the orthogonal polarization sent back from the receiving point.
International Journal of Satellite Communications 03/2007; 6(1):41 - 52.
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ABSTRACT: The Bode-Fano integral is proposed as an objective tool for assessing the bandwidth of antennas and special schemes for antenna bandwidth improvement. The limiting gain-bandwidth product is a measure of optimum power transfer from source to loads. For loads represented in Darlington canonical form, optimum tolerance can be calculated using the Bode-Fano theory. In this paper for the first time the Fano limit has been calculated for loads with up to four reactive elements. It was note that even though increasing the substrate height of coaxially feed microstrip patch antennas will increase the antenna bandwidth; however this is only true up to some specific heights and afterwards the antenna potential bandwidth decreases for future increase in substrate height. Also for double resonance circuits it was concluded that the maximum potential bandwidth is obtained if the two resonant frequencies are the same
RF and Microwave Conference, 2006. RFM 2006. International; 10/2006
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ABSTRACT: A shaping technique for the radiator of an active patch antenna is described, and shown experimentally to reduce harmonic radiation and therefore enhances the conversion efficiency. The perturbation of resonant mode frequencies in a deformed rectangular patch radiator is discussed as a possible basis for systematic design. Various techniques of plotting results were employed for maximum understanding
Electrotechnical Conference, 2006. MELECON 2006. IEEE Mediterranean; 06/2006
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05/2006: pages 91 - 208; , ISBN: 9780470012758
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ABSTRACT: The bandwidth of a microstrip patch antenna is expressed in terms of minimum achievable reflection coefficient using an equivalent circuit and the Bode-Fano theory. The bandwidth-reflection coefficient product is found to be proportional to antenna height and largely independent of feed probe position, for small bandwidths. The product can be computed directly from a numerical evaluation of the first-order Bode-Fano integral. Curves are presented showing how the product becomes limited by the feed probe inductance at very large bandwidths. It is concluded that this effect is unlikely to be a limit on the potential bandwidth of a practical patch antenna. If as a minimal correction the feed inductance is tuned out, the realized bandwidth with low order matching or optimal over-coupling shows the expected relationship to the theoretical limit.
IEEE Transactions on Antennas and Propagation 05/2006; · 2.15 Impact Factor
