Dragan I. Olcan

Multiminima heuristic methods for antenna optimization

Two general approaches to multiminima optimization are considered. The first approach is based on repetition of a single minima method (e.g., the Nelder-Mead simplex applied to the best solution in a set of random trials). The second approach is based on a coarse estimation of local minima using initial set of points and local optimization starting from these local minima (e.g., random search as a generator of the initial set of points and Nelder-Mead simplex as a local optimizer). A comparison of various optimization algorithms has been done on one analytical problem and two well-known examples of antenna design. It is found that: a) the multiminima method based on coarse estimation enables finding more minima with smaller number of iterations than that based on repetition, b) the best multiminima methods are comparable with the best single minima methods in a number of iterations needed for finding the global minima, and c) the multiminima method based on coarse estimation restarted with different weighting coefficients of multiobjective cost function enables efficient Pareto optimization

Solving electrically large EM problems by using out-of-core solver accelerated with multiple graphical processing units

We present results for frequency-domain MoM simulations of electrically large structures using out-of-core solver accelerated with multiple GPUs on a single personal computer. The structures analyzed in order to demonstrate the efficiency of proposed out-of-core solver are Cassegrain reflector antenna with up to 240 λ reflector diameter and Luneburg lens, up to 16 λ diameter, excited with a half-wavelength dipole. The acceleration of out-of-core solver is up to 10 times with one GPU compared to a standard CPU, or up to 20 times when using 3 GPUs.

On the optimal dimensions of helical antenna with truncated-cone reflector

This paper presents optimization of a helical antenna with a truncated-cone reflector. We have found that the dimensions of the truncated-cone reflector and the dimensions of the helical antenna need to be optimized simultaneously to obtain the optimal design. Furthermore, we have found that the truncated-cone reflector can significantly increase the gain of the helical antenna compared to a circular or a square flat reflector. A set of diagrams is made to enable simple design of helical antennas with truncated-cone reflectors. Finally, the results are experimentally verified.

On the Efficiency of Particle Swarm Optimizer when Applied to Antenna Optimization

This paper presents the results for three different antenna optimization problems that are found using the particle swarm optimizer (PSO). The outcomes found with PSO are compared to the outcomes found with other optimization algorithms to estimate the efficiency of PSO. The first problem is finding the optimal position of the feeding probe in a radiating rectangular waveguide. The second problem is finding the maximal forward gain of a Yagi antenna. The third problem is finding the optimal feeding of a broadside antenna array. The optimization problems have 2, 6, and 20 optimization variables respectively

Diakoptic Approach Combining Finite-Element Method and Method of Moments in Analysis of Inhomogeneous Anisotropic Dielectric and Magnetic Scatterers

Abstract A new diakoptic method combining the finite-element method and the method of moments is proposed for analysis of inhomogeneous anisotropic dielectric and magnetic scatterers. The method splits the original electromagnetic system into a number of closed-region finite-element method subsystems containing material complexities and an open-region method of moments subsystem, which are analyzed independently. The solution to the original problem is obtained from linear relations between coefficients in expansions of equivalent electric and magnetic surface currents on diakoptic boundary surfaces. Diakoptic electric sources and the magnetic field in finite-element method subsystems are connected using dual sets of higher-order hierarchical basis functions.

Diakoptic higher-order FEM-MoM approach

The principal objective of the work presented here is to demonstrate the proof-of-concept of coupling a higher-order finite element method (FEM) with a higher-order surface integral equation (SIE) method of moments (MoM) using the diakoptic approach. The diakoptic MoM-SIE approach has been successfully used for the electromagnetic (EM) analysis of microwave transmission lines, large scatterers, and antenna arrays [1], [2]. The diakoptic approach in this work uses coefficients calculated by a higher-order FEM code [3] and a higher-order MoM code [4], [5], and combines them to obtain the solution of the original EM problem. We briefly present the theory behind the concept and results for a case where the proposed approach is successfully applied with some diakoptic subsystems being solved using the FEM and the others using the MoM-SIE formulation.

Diakoptic surface integral-equation formulation applied to large antenna arrays

Diakoptic surface integral-equation formulation is used to efficiently simulate large antenna arrays, modeled as 3D EM structures. The significant accelerations and storage reductions are achieved, when compared to the classical MoM-SIE. Both near field and far field (radiation pattern) of the arrays, calculated using DSIE, match the results calculated using MoM-SIE very well (the maximal relative error is about 1% calculated with respect to peak values). The future work will include diakoptic boundaries with common walls, application of DSIE to optimization of complex EM structures and calculation of EM time-domain responses, and hybridization with other numerical techniques such as finite elements and volume integral-equation formulation.

Diakoptic Approach to Analysis of Microwave Transmission Lines

We present a diakoptic approach to analysis of microwave transmission lines. The approach is based on the equivalence theorem. Presented results show that the diakoptic approach is much faster than the simultaneous analysis of the whole system. The proposed diakoptic approach decomposes the problem into smaller problems that can be independently solved, which makes this approach suitable for implementation on parallel processors

Modeling of human bodies for analysis of wireless body area networks in crowds

We present an approach for modeling of human bodies in crowds for the analysis of channel parameters in wireless body area networks. The approach uses distributed surface impedances with method of moments based on surface integral-equation formulation. It significantly reduced the computer resources needed for the electromagnetic analysis, and keeps the final results accurate in a statistical sense.

Comparison of Differential evolution and Cuckoo optimization for antenna array problems

We present comparison of Differential evolution and Cuckoo search for optimization of linear antenna array of Hertzian dipoles. The amplitudes of excitations are optimized in order to minimize sidelobe levels. The results are compared for 42 elements array, with 20 optimization variables. The conclusion is that classic Differential evolution provides better convergence for this particular problem than standard Cuckoo search.