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In this paper, a hybrid approach for the synthesis of the ldquooptimalrdquo compromise between sum and difference patterns for subarrayed monopulse antennas is presented. First, the subarray configuration is determined by exploiting the knowledge of the optimum difference mode coefficients to reduce the dimension of the searching space. In the second step, the subarray weights are computed by means of a convex programming procedure, which takes advantages from the convexity, for a fixed clustering, of the problem at hand. A set of representative results is reported to assess the effectiveness of the proposed approach. Comparisons with state-of-the-art techniques are also presented. (c) 2009 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

In this paper, an innovative technique for the determination of the dielectric properties of planar substrates is presented. Starting from a set of impedance measurements performed on a section of a microstrip transmission line built on the planar dielectric substrate under test, the proposed technique formulates the reconstruction problem in terms of an optimization one successively solved by means of an effective stochastic algorithm. Such a method allows one the reconstruction of the permittivity values at multiple frequencies by simply using a vector network analyzer and a standard calibration procedure for the impedance measurement. The results of some representative experimental tests are shown for a preliminary assessment of the effectiveness of the proposed approach. (c) The Electromagnetics Academy - The final version of this article is available at the url of the journal PIER M: http://www.jpier.org/PIERM/pier.php?paper=09112901

This paper is aimed at presenting a numerical study on the reconstruction accuracy (quantitative imaging) of the integrated genetic algorithm (GA)-based multicrack strategy, thus completing the assessment previously carried out and limited to verify the accuracy of the qualitative imaging (i.e., crack detection, location, and size estimation). The obtained results prove an acceptable reliability and accuracy of the GAbased integrated strategy also in reconstructing multiple defective regions even though the resulting performances degrade in comparison with those achieved by the same approach when used for qualitative imaging purposes. (c) 2007 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

Due to specific requirements for automotive applications, the design of an integrated antenna system able to guarantee the connection to several wireless services, i.e. GPS, GSM/GPRS and COSPAS-SARSAT, must be faced as an optimization problem. Starting from electrical and geometrical constraints, the design of the antenna must be faced considering, in addition to usual antenna design procedures, also interferences phenomena arising from the integration of antennas belonging to different classes in a single compact device. In the paper are described the design phases of the device and the experimental and numerical validation activity conducted on a prototype of the antenna.

In this letter, the design of a quad-band antenna is presented. The antenna has a planar geometry printed on a dielectric substrate orthogonal to a reference ground plane and its geometrical parameters are optimized starting from a Hilbertlike pre-fractal reference shape. The reliability of the synthesized antenna is assessed by means of a set of experimental tests to verify its compliance with the project constraints. (c) 2009 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

In this letter, a planar Ultra WideBand (UWB)antenna suitable for the integration in wireless Universal Serial Bus (USB) dongles is described. The antenna has a bandwidth equal to 2GHz from 3GHz up to 5GHz with return loss values below −10 dB in the whole frequency range. To comply with UWB system needs, the antenna presents good distortionless properties when employed in a TX/RX system. Moreover, thanks to its simple shape and miniaturized geometry, the proposed prototype can be easily integrated and printed on dongle PCBs. In order to assess the reliability and efficiency of the antenna, a selected set of results from the experimental validation are shown and compared with the outcomes of the numerical simulations carried out during the synthesis process. (c) 2008 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

In this letter, an experimental validation of percolation-based approaches for the prediction of wave propagation in random media is presented. Measurements are collected in a real controlled environment, where the obstacles are stochastically placed in a two-dimensional grid according to a known non-uniform density distribution. The obtained results show that, in spite of their simplicity, percolation-based approaches can be applied in real propagation problems. The definitive version is available at www3.interscience.wiley.com

The advantages of MIMO technology in UWB communication systems are investigated evaluating the channel capacity from measurements taken in indoor environments. The results suggest that in practical instances spatial diversity is more attractive than spatial multiplexing for UWB systems. (c) 2008 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

Synthesis of ultrawideband (UWB) antennas by means of a particle swarm optimizer (PSO)-driven spline-based shaping approach is described. In order to devise a reliable and effective solution, such a topic is analyzed according to different perspectives: 1) representation of the antenna shape with a simple and efficient description; 2) definition of a suitable description of the UWB Tx/Rx system; 3) formulation of the synthesis problem in terms of an optimization one; 4) integration of the modelling of the UWB system into a computationally efficient minimization procedure. As a result, an innovative synthesis technique based on the PSO-based iterative evolution of suitable shape descriptors is carefully detailed. To assess the effectiveness of the proposed method, a set of representative numerical simulations are performed and the results are compared with the measurements from experimental prototypes built according to the design specifications coming from the optimization procedure. To focus on the main advantages and features of the proposed approach, comparisons with the results obtained with a standard parametric approach are reported, as well. (c) 2008 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

In this letter, the structure of the prototype of a smart antenna working in the 2.4 GHz band is described. The radiating structure is composed by a 8-elements linear array with a finite reflecting plane and its adaptive behaviour is obtained by means of a set of electronically-driven vector modulators that control the array weights. The antenna system is equipped with a control software based on a Particle Swarm Optimizer (PSO) algorithm that enables the system to adapt to the complex interference scenario. A selected set of numerical and experimental results are reported and discussed to assess the effectiveness of the proposed architecture. The definitive version is available at www3.interscience.wiley.com

The architecture of a fully-adaptive smart antenna working in the 2.4 GHz band is described and its functionalities preliminarily assessed. The radiating unity consists of an eight-element linear array of dipoles with a finite reflecting plane. The adaptive behaviour is achieved by means of a set of electronically-driven vector modulators that realise the array weights. The capability to react in real-time to complex interference scenarios is provided by an SW control module based on the particle swarm optimiser (PSO) algorithm. To assess the effectiveness of such an implementation, a selected set of results is reported and discussed. This paper is a postprint of a paper submitted to and accepted for publication in Electronics Letters and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library.

In this letter, the synthesis of a miniaturized threeband planar antenna working in GSM and WiFi frequency bands is described. The reference geometry for the synthesis of the antenna is a hybrid prefractal shape obtained by integrating a Sierpinski-like and a Meander-like structure. The synthesis of the geometrical parameters of the antenna has been performed by means of a customized Particle Swarm strategy to yield electrical parameters within given specifications. In order to show the effectiveness of the approach, some results from the numerical synthesis procedure are described and a comparison between simulations and experimental measurements is reported.

In this letter, the design of a microstrip three-band antenna working in GPS, GSM and Wi-Fi frequency bands is described. By considering a planar geometry printed on a dielectric substrate, the tuning of the antenna behavior in three non-harmonic frequency bands is obtained perturbing the patch perimeter according to a Koch-like fractal shape. The synthesis procedure is automatically performed by means of an iterative PSO-based optimization strategy where a fractal boundary generator is integrated with a MoM-based electromagnetic simulator. The feasibility of the approach as well as the reliability of the synthesized antenna is assessed through simulations as well as experimental results. The definitive version is available at www3.interscience.wiley.com

A spline-shaped antenna for Ultra-Wideband (UWB) communications that operates in the Electronic Communications Committee (ECC) released band from 6 GHz up to 8.5 GHz is described. Selected simulated and measured data are reported to assess the achieved impedance matching over the whole band of interest, and the distortionless behavior as well as to show the omnidirectional radiation properties. This paper is a postprint of a paper submitted to and accepted for publication in Electronics Letters and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library.

A set of representative results are presented that are obtained with two multiresolution strategies developed for dealing with multifrequency inverse scattering experiments starting from the iterative multiscaling approach previously studied for monochromatic illuminations. The first approach is concerned with the integration of the iterative multiscaling algorithm into a frequency-hopping reconstruction scheme, while the second one allows a multiresolution simultaneous processing of multifrequency data. The numerical and the experimental analysis are aimed at assessing both the reconstruction effectiveness and the required computational costs of the two- and three-dimensional implementations of the proposed inversion schemes in comparison with the monochromatic multistep process and to the single-step optimization strategy, as well. (c) 2007 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

In this paper and its companion, the problem of ray propagation in nonuniform random half-plane lattices is considered. This paper was published in Journal of the Optical Society of America. A, Optics, image science, and vision and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/abstract.cfm?uri=josaa-24-8-2363. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.

Designing customized EMI filters is a challenging task since the choice of the circuit topology as well as of the discrete values of the electric components, for satisfying multiple electrical requirements, is not trivial and no-standard guidelines are available. In this letter, an approach based on a particle swarm optimizer, used in conjunction with a circuital simulator, is described. By using equivalent models of commercial components, such a method allows the synthesis of reliable and ready-to-build filters. As an example, a filter prototype is realized and its efficiency assessed through numerical and experimental evaluations. This paper is a postprint of a paper submitted to and accepted for publication in Electronics Letters and is subject to Institution of Engineering and Technology Copyright. The copy of record is available at IET Digital Library.

In this letter, the synthesis of a three-band patch antenna working in E5-L1 Galileo and Wi − Max frequency bands is described. The geometry of the antenna is defined by performing a Koch-like erosion in a classical rectangular patch structure according to a Particle Swarm strategy to optimize the values of the electrical parameters within given specifications. In order to assess the effectiveness of the antenna design, some results from the numerical synthesis procedure are described and a comparison between simulations and experimental measurements is reported. (c) 2007 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

In this paper a new approach to the control of phased arrays is presented and assessed. Starting from the adaptive array theory, a particle swarm strategy is used to tune the phase coefficients of the array in order to adaptively minimize/avoid the effects of interfering signals at the receiver. To show the effectiveness of the proposed approach, a selected set of numerical examples, concerned with linear as well as planar arrays, is presented. Furthermore, to evaluate the advantages of the PSO-based strategy over state-of-art methods, a comparative study is carried out by analyzing the performance of the method in terms of both the signal-to-interference-plus-noise-ratio and resulting beam pattern. The achieved results, even though preliminarly, seem to confirm that the PSO-based approach satisfactorily works and it generally outperforms previously proposed/state-of-art phase-only adaptive control strategies. (c) 2006 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

The development of efficient automotive accident management systems requires the design of complex multifunction antennas enabling different wireless services (e.g., localization, voice and data communications, emergency calls, etc.). Starting from different specifications (electrical, mechanical, and aerodynamic), the design of a multifunction antenna must consider, in addition to the usual antenna design requirements, also interference phenomena arising from the integration of different classes of antennas in a compact device. In this framework, the paper describes a methodology based on a stochastic multiphases optimization approach for the design of an integrated multifunction/multiband antenna system. Moreover, for an exhaustive assessment, the results of an experimental validation performed on a prototype of the multifunction antenna system are shown and discussed. (c) 2006 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.

In this letter, the design of a monopolar dual-band antenna operating in the L1 and L2 GPS bands is presented. The prefractal geometry of the antenna has been synthesized by means of a particle swarm algorithm for optimizing the values of the electrical parameters within the specifications. For a general assessment, some selected results of numerical simulations are shown and some comparisons between numerical data and experimental measurements are presented. (c) 2006 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.