PROJEKTI
   

Project
Acronym: CylCloak 
Name: Metamaterial-Based Cylinders Used for Invisible Cloak Realization 
Project status: From: 2010-07-22 To: 2011-07-21 (Completed)
Contract number: FA8655-10-1-3024 
Action line: EOARD - European Office of Aerospace Research and Development  
Type (Programme): Ostali 
Instrument:  
Project cost: 30.000,00 USD
Project funding: 30.000,00 USD
Project coordinator
Organisation Name: University of Zagreb Faculty of Electrical Engineering and Computing 
Organisation adress: Unska 3 
Organisation country: Hrvatska 
Contact person name: Zvonimir Šipuš 
Contact person email: Email 
Croatian partner
Organisation name: Fakultet elektrotehnike i računarstva 
Organisation address: Unska 3 
Contact person name: Zvonimir Šipuš
Contact person tel:
+385 1 6129 798  Contact person fax: +385 1 5129 717 
Contact person e-mail: Email 
Partners
Organisation nameCountry
Short description of project
Uniaxial cylindrical cloaks have recently been proposed to prevent scattering of electromagnetic waves, i.e. to render objects invisible. The proposed cloaks with reduced variation of constitutive parameters suffer from nonzero reflectance, i.e. they are only partly invisible. Therefore, we propose a 12-month effort to develop an analysis method and the corresponding software for analyzing cylinders made from metamaterial-based concentric layers with an application to invisible cloak realization. The main parameter of interest is the scattered field, i.e. if the considered structure really appears invisible to the incident wave. The considered structure will be modeled as a multilayer anisotropic cylinder where both permittivity and permeability tensors are diagonal in the cylindrical coordinate system. The active cloaks can be also analyzed in this way since their homogeneous electromagnetic model is based on complex constitutive parameters.  The proposed analysis method includes transient analysis, i.e. by this it is possible to determine response to the pulse excitation (for example, response to the radar signal). The proposed analysis method will be connected with a suitable global optimization routine, and the developed software package will be used to design an experimental prototype. A possible application of the considered prototype is reduction of scattered field from mechanical structures that need to be placed in front of big antennas, such as radar antennas or reflector systems. 
Short description of the task performed by Croatian partner
The work in the project will be divided in the following tasks: (a) Extension of the program for analyzing uniaxial multilayer cylinders – with the extended version it will be possible to analyze the case when the incident field has oblique direction of propagation and oblique polarization. (2) Merging of the program for analyzing uniaxial cylindrical structures with the global optimization program. As a global optimization algorithm we have chosen the Particle Swarm Optimization (PSO) algorithm. This is an evolutionary algorithm similar to the genetic algorithm and to the simulated annealing, but it operates on a model of social interactions between independent agents and utilizes swarm intelligence to achieve the goal of optimization problems. It was chosen here since the associated algorithm has the same or better performances comparing to other global optimization programs. (3) Extension of the program in order to include the transient analysis of the structure. One of the goals of the cloak investigation is to make the cloaks invisible to radar signals. In order to design such a cloak it is not enough the perform time-harmonic analysis, i.e. the response of the structure to the pulse excitation should be also determined and taken into account in the design procedure. (4)  Extension of the program to include cloaks with active components. Active cloaks can be electromagnetically modeled using asymptotic homogenized material parameters, and the gain inside such a structure can be taken into account if the structure is described with complex unisotropic permittivity and permeability tensors. (5) Making a proposal for building an experimental model of a cloak. The goal is to develop the experimental model that is relatively simply to build, and that is invisible  for arbitrary-polarized electromagnetic waves in a large frequency bandwidth. The selection of the propsed type of structure will be based on the results of the performed analysis. The proposed model will be a prototype of the structure that reduces scattered field if some mechanical supporting structure needs to be placed in front of the antenna.   


   

Design by: M. Mačinković

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