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PROJECT 245 : SOME KEY ACHIEVEMENTS |
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Working Group I: Antenna modeling and
CAD tools
Considerable progress in the theoretical modeling of multilayer printed antennas has been achieved by university teams involved in the project.
First, new approaches have been developped to model complex structures with multiple interconnected layers, incorporating lossy and inhomogeneous dielectric materials. Another effort has been devoted to speeding up computations for medium size arrays by developing new methods to simplify mutual coupling computation, without loss of accuracy.
As a result, two complementary CAD tools PSALM (CH) and MAGMAS (B) have been developed, validated and documented. They now start to be used in industry. These tools are one generation ahead of commercially available CAD software. Presently developed in stand alone versions,their integration into a general Antenna Design Framework (ADF) is underway.
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Fig. 5 Mathematical modelling of mutual coupling between printed antennas (Courtesy LEMA-EPFL, Switzerland ) Performing fundamental research on the electromagnetic modelling of multilayered printed antennas has been a key issue in the COST Project 245. The fig.5 shows a mathematical function of two variables which correspond to real and imaginary part of a complex variable. This function accurately models the coupling phenomena between two patches belonging to a printed array antenna. In order to evaluate the coupling coefficients (an essential quantity for antenna designers), the function must be integrated along the real axis. Unfortunately, the function has an abrupt behavior on this axis, showing jagged peaks separated by deep canyons and a hilly behaviour which increases without limit. Hence, computer evaluation of mutual coupling used to be a very expensive and time-consuming calculation. But mathematical considerations prompt us to modify the integration strategy by making a detour inside the complex plane. There we can go around the peaks and through the passes by moving across a gentle landscape of rolling hills and smooth valleys. This reduces dramatically the computer effort and brings under our analysis capabilities much more complicated antenna configurations (WS Proc. p 31). |
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Fig. 6 Small color picture of a microstrip array under test in the anechoic chamber at the Catholic University of Leuven (Courtesy KUL, Belgium) |
In the modeling of planar antenna arrays, one of the main topics COST Project 245, a fundamental problem is the modeling of the mutual coupling between the different array elements. At the Catholic University of Leuven a new concept (the so-called Expansion Wave Concept) was developed to solve this problem. The result of the scheme is a reduction of the number of unknowns describing the problem with one to two orders of magnitude. The antenna depicted in the fig. 6 was used to verify the new concept experimentally. It is a representative 8x8 planar array. Extensive comparison of measured and calculated coupling coefficients proved the accuracy of the new technique. However, this is not the end... The fundamental nature of the new concept allows to use it also to model the lateral finiteness of practical antenna arrays, something which certainly has to be looked at in future theoretical modeling work. (WS Proc. p 43, 149) |
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Fig. 7 The antenna design framework (Courtesy of IDS, Italy) The fig. 7 shows a typical Antenna Design Framework working screen. Electromagnetic engineering requires sophisticated modeling tools to achieve shorter development cycles. High accuracy is sought in the performance estimates from the very early development stages. The quest for optimum performances demands the assessment of a wide spectrum of solutions, often under the high pressure and tight schedule of tender preparation. The Antenna Design Framework (ADF) has been conceived by the European Space Agency and developed by IDS - Ingegneria dei Sistemi S.p.A. to make modern computational technologies available to electromagnetic engineers. It has been designed to support both the development and the use of advanced modeling tools. It is applicable to single antennas, arrays and reflector antennas isolated or in presence of a vehicle or support. The system operates through a visual metaphor of the design process, logically grouping the design components into higher level blocks and with the corresponding modeling tools and services. All functions are accessed by means of a uniform data-based mechanism, which is fully independent from the tools used to actually perform each operation. The Antenna Design Framework development activity is integrated in the "Modeling and Analysis" COST 245 Working Group, due to the strong coordination fostered by ESA in order to obtain a common framework for software tools in the frame of antenna design. The new v 2.0 release of ADF was introduced at COST 245 - ESA Workshop on Active Antennas (WS Proc. p 145) |
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COST-245 Summary report |
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Mars 1997 Content Responsible : Technical Manager : Webmaster@lema.epfl.ch |
