Parameterization of Arbitrary Geometrical Structures for Automated Electromagnetic Optimization
J.W. Bandler, R.M. Biernacki and
S.H. Chen
ABSTRACT
For the first time, this paper reveals and discusses the theoretical foundation of the Geometry Capture technique. Geometry Capture facilitates user-parameterization, through graphical means, of arbitrary 2D and 3D geometrical structures. This makes it possible to optimize the shape and dimensions of geometrical objects in an automated electromagnetic design process by adjusting the user-defined parameters subject to explicit numerical bounds and implicit topological constraints.
SUMMARY
Recent research results [1-5] and the corresponding explosion of available electromagnetic (EM) simulators (e.g., [6-11]) are important factors in the development of a new generation of microwave design tools. Advances in computer hardware make this approach feasible, though still very CPU intensive. The potential and importance of EM-based optimal design have been fully confirmed by recent events [12,13] and we expect widespread use of this approach in the future. The number of reported applications is already growing rapidly.
Automated EM optimization raises a number of challenges. Some have been already successfully addressed [14-18] including geometrical interpolation and modeling, reconciling and exploiting the discrete nature of numerical EM solvers with the requirement of continuous variables and gradients by the optimizers, as well as parallel computation combined with efficient data base handling. Techniques, such as Space Mapping [19,20] will play a pivotal role in effective utilization of EM design tools.
This paper addresses the critical issue (see [21]) of parameterization of geometrical structures for the purpose of layout-based design, in particular automated EM optimization. As the optimization process proceeds, revised structures must be automatically generated. Moreover, each such structure must be physically meaningful and should follow the designer's intention w.r.t. allowable modifications and possible limits. It is of utmost importance to leave the parameterization process to the user. In our earlier work (Empipe Version 1.1, 1992) we created a library of predefined elements (lines, junctions, bends, gaps, etc.), that were already parameterized and ready for optimization. The applicability of that approach is, however, limited to structures that are decomposable into the available library elements. No library, no matter how comprehensive, will satisfy all microwave designers, simply because of their creativity in devising new structures. Moreover, the library approach inherently omits possible proximity couplings between the elements since they are individually simulated by an EM solver and connected by a circuit-level simulator.
