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A Hybrid Approach to the Synthesis of Sub-Arrayed Monopulse Linear Arrays
No full textIn 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
A Monopolar Quad-Band Antenna based on a Hilbert Self-Affine Pre-Fractal Geometry
No full textIn 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
Multiple-Shape Reconstruction by Means of Multiregion Level Sets
No full textIn the framework of inverse scattering techniques for microwave imaging, this paper proposes an approach based on the integration between a multiscaling procedure and the level-set-based optimization in order to properly deal with the shape reconstruction of multiple and disconnected homogeneous scatterers. The effectiveness and robustness of the proposed approach is assessed against both synthetic and experimental data. A selected set of results concerned with complex shapes is presented and discussed. "(c) 2010 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.
Bayesian Compressive Sampling for Pattern Synthesis With Maximally Sparse Non-Uniform Linear Arrays
No full textA numerically-efficient technique based on the Bayesian compressive sampling (BCS) for the design of maximally-sparse linear arrays is introduced. The method is based on a probabilistic formulation of the array synthesis and it exploits a fast relevance vector machine (RVM) for the problem solution. The proposed approach allows the design of linear arrangements fitting desired power patterns with a reduced number of non-uniformly spaced active elements. The numerical validation assesses the effectiveness and computational efficiency of the proposed approach as a suitable complement to existing state-of-the-art techniques for the design of sparse arrays. “(c) 2011 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.
Planar monopole UWB antenna with WLAN-band notched characteristics
No full textIn this paper, a planar monopole antenna for Ultra-Wideband (UWB) communications with a notched behavior in the two sub-bands UNII1 and UNII2 of the Wireless Local Area Network (WLAN) band is presented. The antenna geometry is described by means of a spline curve and a rectangular slot. Numerical and experimental results are reported to assess the effectiveness of the proposed design in terms of impedance matching and radiation characteristics. “(c) The Electromagnetic Accademy. The final version of this article is available at the url of the journal PIERB http://www.jpier.org
DERA: A Faceted Knowledge Organization Framework
No full textThe availability of a priori knowledge, also called background knowledge, is fundamental for the functioning of semantics based systems. In this paper we introduce a faceted knowledge organization framework called DERA (for Domain, Entity, Relation, Attribute) and describe its implementation inside a system, called UK (for Universal Knowledge) which is extensible and scalable and which allows for fully automated reasoning via a direct encoding into Description Logics (DL). Extendibility and scalability is obtained by allowing the definition of any number of domains, where a domain is taken to be an area of knowledge or field of study that we are interested in or that we are communicating about. In turn, a domain is organized into a number of facets where a facet is taken to be a hierarchy of homogeneous terms describing an aspect of the knowledge being codified, where each term denotes a primitive atomic concept‖. Domains, facets, terms can be added at any time, and the different applications can use any subset of them. The direct encoding of DERA into DL is obtained by allowing only three types of facets (i.e., Entity, Relation, Attribute) which can be directly translated into DL concepts, roles, attributes, or into instances whose properties are encoded using the terms occurring in the facets themselves. The current implementation of UK contains around 377 Domains, out of which 115 are in priority for development, more than 150,000 terms (encoding concepts, relations and attributes), around 10,000,000 instances and more than 93,000,000 axioms codified using the terms codified in the DERA facets
Validation of a Smart Antenna Prototype: Model and Experiments
No full textIn this paper, the architecture of a smart antenna prototype is described and its functionality assessed. The system prototype is composed by an 8-elements linear array of dipoles with a finite reflecting plane and the adaptive behavior is obtained modifying a set of array weights with electronically-driven vector modulators. In order to real-time react to complex interference scenarios, the system is controlled by a software control module based on a Particle Swarm Optimizer. To demonstrate the feasibility and the effectiveness of the proposed implementation, a set of representative results concerned with realistic interference scenarios is reported and discussed
A Comparison Between Deterministic and Stochastic Inversions of Phaseless Data for Microwave Imaging
No full textThe development of microwave imaging techniques and their application are strongly related to the possibility to realize fast and cheap measurement systems. On the contrary, the phase acquisition usually requires complex and expensive apparatus and it turns out to be critical especially at high frequencies. Moreover, holographic and interferometric methods, often used in optical applications [1], are usually characterized by a high computational burden because of the time‐consuming data post‐processing. Consequently, the study of efficient algorithms for the reconstruction from amplitude‐only data is necessary in several applications. Also published in: Progress In Electromagnetics Research Symposium Abstracts, Hangzhou, China, March 24-28, 200
Complex Synthesis of Antenna Structures Through Evolutionary-Optimization Techniques
No full textIn this paper, three antenna problems concerned with both the synthesis and the control (i.e., a real�]time synthesis) are formulated and solved by using innovative and ad�]hoc versions of evolutionary optimization techniques. In order to assess the effectiveness of the proposed techniques, some representative results are compared with those obtained with standard versions of optimizers or state�]of�]the�]art deterministic approaches. This is the author's version of the final version available at IEEE
Design of Non-Harmonic Multi-Band Pre-Fractal Antennas
No full textIn this paper, an innovative fractal�]based methodology is proposed for synthesizing antennas with complete and unconstrained multi�]band behaviors. By assuming pre�]fractal geometries as reference structures, the synthesis process is faced with an optimization procedure aimed at suitably tuning the geometrical characteristics of the antenna. In order to preliminary assess the effectiveness and accuracy of the proposed approach, the design of a planar dual�]band GPS (1L42,15751=Lf MHz) and ( MHz) antenna is described and discussed. This is the author's version of the final version available at IEEE