1869 research outputs found
Sort by
Optimization of a Spline-Shaped UWB Antenna by PSO
No full textThis letter presents the design of a planar antenna for U W B applications with a bandwidth of 5.5 GHz over 3.7 to 9.2 GHz and return loss values lower than −10 dB. The antenna geometry is described in terms of a spline-based representation whose control parameters, together with other geometrical descriptive quantities, are determined through a suitable Particle Swarm optimizer (P SO) in order to fit the U W B requirements. Representative results of both numerical and experimental validations are reported in order to assess the performance of the prototype as well as to give some preliminary indications on the reliability and effectiveness of the whole synthesis approach. (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
An innovative multi-source strategy for enhancing the reconstruction capabilities of inverse scattering techniques
No full textActive microwave imaging techniques are aimed at reconstructing an unknown region under test by means of suitable inversion algorithms starting from the measurement of the scattered electromagnetic field. Within such a framework, this paper focuses on an innovative strategy that fully exploits the information arising from the illumination of the investigation domain with different configurations as well as radiation patterns of the probing sources. The proposed approach can be easily integrated with multiview techniques and, unlike multifrequency methods, it does not require additive a-priori information on the dielectric nature of the scatterer under test. A large number of numerical simulations concerned with 2D geometries confirms the effectiveness of the inversion strategy as well as its robustness with respect to noise on data. Moreover, the results of a comparative study with single-source methodologies further point out the advantages and potentialities of the new approach. “(c) The Electromagnetics Academy - The final version of this article is available at the url of the journal PIER (Progress In Electromagnetics Research): http://www.jpier.org/PIER/pier.php?paper=0912080
Genetically-designed arbitrary length almost difference sets
No full textAlmost difference sets (ADSs) have important applications in cryptography, coding theory, and antenna array thinning. A new approach is proposed to derive ADSs of arbitrary lengths. Such a technique recasts the ADS design as a combinatorial optimisation problem successively solved by means of a suitable binary genetic algorithm. New ADSs are derived to assess the effectiveness of the proposed approach. "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"
Improving the Reconstruction Accuracy of Inversion Strategies Through Energetic Constraints
No full textMicrowave imaging techniques are widely investigated in many applied sciences such as the subsurface prospecting [1] and the medical diagnosis [2]. Unfortunately, when inverse scattering approaches are considered, the drawbacks of non‐linearity and ill‐posedness [3] have unavoidably to be dealt with. Therefore, the problem at hand is usually recast as the minimization of a suitable cost function to be properly minimized in order to find the optimal solution. Such a cost function is usually defined by two discrepancy terms based on the knowledge of the scattered field measured in a suitable observation region and of the incident field in the investigation region. Moreover, further regularization terms have been studied and successfully applied in order to enhance the quality of the reconstructions (e.g., [4][5]). In such a framework, this contribution presents a new constraint based on the conservation of energy to improve the reconstruction accuracy of inverse scattering procedures
Passive Real-Time Localization Through Wireless Sensor Networks
No full textLocalization and tracking play a key role in several applications both civilian and military [1]. The growing needs of remote monitoring private and public areas caused a fast development of wireless and pervasive systems. In such a framework, the availability of low‐power devices integrating on‐board processing and wireless communication stimulated several studies in efficient collaborative signal processing algorithms for tracking purposes. Most of them are based on the exploitation of data collected by dedicated sensor or they assume the target equipped with a transmitting device [2]. In this work, an innovative approach based on a LBE strategy to localize and track passive objects is presented. The localization problem is addressed only by considering the available received signal strength indicator (RSSI) at the nodes of a wireless sensor network (WSN) deployed in the environment and without any additional on board sensor
Qualitative Microwave Subsurface Imaging by Means of a Multi-Resolution Multi-Region Level Set Method
No full textSubsurface sensing is a wide branch of non�]invasive diagnostic concerned with the detection of unexploded ordnance as well as oilfield discovery. In this framework, many approaches have been proposed by considering different probing techniques as for instance x�]rays, ultrasonics, eddy currents, and microwaves. Also published in: Progress In Electromagnetics Research Symposium Abstracts, Hangzhou, China, March 24-28, 200
On the Effects of the Exploitation of Source Diversity in Aspect-Limited Multi-View Microwave Imaging Systems
No full textThe reconstruction of unknown regions through active microwave imaging techniques requires the retrieval of a large amount of unknown parameters if one aims at fully characterize the electromagnetic properties of the targets under test. Unfortunately, a limited number of independent measurements is available, especially when the scattered field is undersampled because of intrinsic limitations of the imaging setup. In this context, the paper investigates the potentialities of a methodology based on a multi�]source illumination as a possible strategy for compensating the reduction of informative field measures and improving the imaging accuracy with respect to single�]source experiments. This is the author's version of the final version available at IEEE
Semantic Annotation of Images on Flickr
No full textIn this paper we introduce an application that allows its users to have an explicit control on the meaning of tags they use when uploading photos on Flickr. In fact, this application provides to the users an improved interface with which they can add concepts to photos instead of simple free-text tags. They can thus directly provide semantic tags for their photos that can then be used to improve services such as search. The original publication is available at www.springerlink.co
A Miniaturization Process of an Antenna With Pre-Fractal Geometry by Means of a Particle Swarm Optimization
No full textThis work presents a synthesis procedure for designing miniaturized pre-fractal antennas for wireless applications. In order to minimize the linear dimensions of the antenna and to obtain Voltage Standing Wave Ratio values within specifications, the device configuration has been synthesized by defining a suitable building pre- fractal geometry tuned through a customized Particle Swarm Optimizer. This is the author's version of the final version available at IEEE
Frontiers in Multiple-Agents Evolutionary Techniques Applied to Adaptive Arrays Design
No full textThis paper proposes an innovative approach to control phased arrays. 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. The effectiveness of the proposed approach is assessed through a comparison with state-of-the-art methods. This is the author's version of the final version available at IEEE