Zbyněk Raida

Comparison of novel multi-objective self organizing migrating algorithm with conventional methods

In the paper, three algorithms for the multi-objective optimization based on the strategy of a self-organized migration are compared. The first two algorithms — Weighted Sum Method and Rotated Weighted Metric Method — transform multiple objectives into a single fitness function. The third method — a novel MOSOMA — combines the principle of the non-dominated sorting of population in the objective space and the survey of the decision space of input variables based on the self-organized migration. All three algorithms are compared on the test problem with the Pareto front, which contains both convex and non-convex parts. Monitored parameters are generational distance, spread of solutions and CPU time.

Wide-band dielectric resonator antennas for RF energy harvesting

Energy harvesting seems to be a suitable solution for remote device powering in systems like wireless sensor networks, which are becoming ubiquitous. In presented paper, a wide-band Dielectric Resonator Antenna (DRA) for RF energy harvesting is studied. The frequency band of interest lies between 1.84 GHz and 2.445 GHz, covering three main wireless communication systems, namely Global System for Mobile Communications (GSM) operating on 1800 MHz, Universal Mobile Telecommunications System (UMTS) at 2100 MHz and wireless local area network (WLAN) based on 802.11 IEEE standard [9] at 2400 MHz. Two antennas based on identical bow-tie dielectric resonators with different feeding schemes are proposed. The aperture coupled DRA shows superior performance in terms of impedance matching and stability of the radiation pattern when compared to the probe coupled antenna. The simulation results of these two antennas are compared and experimentally verified by measurements.

Design and optimization of periodic structures for simultaneous EBG and AMC operation

The paper focuses on design and optimization of metallo-dielectric periodic structures with simultaneous electromagnetic band gap (EBG) and artificial magnetic conductor (AMC) behavior in the required frequency band. Three variants of mushroom structures were studied to fulfill the requirements: the two-layer one with simple square metallic patch, the two-layer one with metallic patch of complex shape and the three-layer one with simple square metallic patch at the top and the bottom layer. The structures were tuned using particle swarm optimization (PSO) algorithm implemented in Matlab in connection with CST Microwave Studio (CST MWS) for full-wave dispersion diagram and reflection phase diagram computation. The obtained results were verified by Ansofts High Frequency Structure Simulator (HFSS).

Wideband feeders for millimeter-wave horn antennas

In the paper, the design of millimeter-wave horn antennas is described. Attention is turned to the proper construction of a wideband feeder of the horn. For the final antenna structure, a bow-tie dipole and a Vivaldi antenna were chosen. The antenna construction is aimed to provide a wide bandwidth on one hand and a high gain on the other hand. An experimental comparison of horn antennas fed by a bow-tie dipole and a Vivaldi slot is the original contribution of the paper. Antennas are compared considering computer simulations in CST Microwave Studio and measured data.

Multi-objective Self-organizing Migrating Algorithm

Almost every optimization problem can be viewed as multi-objective one. Multi-objective problems with conflicting objectives lead to so called Pareto front which expresses trade-off among the objectives. Multi-objective techniques yield better understanding of the solved problem because resulting Pareto front expresses the balance between different objectives. In this chapter, fundamentals of multi-objective optimization are reviewed. Then, multi-objective optimization technique based on principle of self-organizing migration is described. The proposed method is able to solve unconstrained, constrained problems having any number of variables and objectives. The method is designed to find so called non-dominated set that covers the true Pareto front uniformly.

Diffraction of electromagnetic wave on skin blood vessel: Statement of the problem

A theoretical model for the diffraction of electromagnetic wave on the skin blood vessel is developed. For this purpose, the Greens function formalism is used. The calculations performed in the paper are based on real experimental data, which makes it more compelling. The proposed approach would eliminate fundamental uncertainties in the modeling of biological tissues.

Diffraction of electromagnetic wave on skin capillary

We have formulated and solved the problem of electromagnetic wave diffraction on skin blood vessel. As an important result of our investigation, it is established that the amplitude of the scattered field is proportional to the square of the capillary area. For the case of long waves, the reflected field is linearly dependent on the depth position of the capillary. The proposed approach would eliminate fundamental uncertainties in the modeling of biological tissues.

Sierpinski conical monopole antennas

Planar Sierpinski monopole exhibits a multi-band behavior. However, the parameters of Sierpinski monopole in operation frequency bands are not optimal. The impedance bandwidth is narrow and radiation pattern is not omni-directional in the horizontal plane because of the rotational asymmetry of the planar antenna. These disadvantages can be eliminated by converting the planar Sierpinski monopole to a conical one. By this conversion, a symmetrical three-dimensional (3-D) structure, which reaches a larger bandwidth and a better radiation pattern, is obtained. In the paper, different versions of the conical Sierpinski monopole are proposed, and results of simulations performed in CST Microwave Studio are mutually compared.

Electromagnetic simulation for certification of small aircraft: Direct and indirect effects of lightning

In the paper, we discuss exploitation of advanced computational electromagnetics (CEM) for the development and certification of small airplanes and their immunity against lightning. CEM is shown to accelerate the development of aircraft and reduce the cost of development. CEM can be used to demonstrate the airplane resistance against lightning strokes and support aircraft certification from viewpoint of electromagnetic compatibility (EMC).

Multi-objective Design of EM Components

Design of EM components is usually very demanding task. It comprises setting of large number of variables. With increasing number of variables, the number of possible combinations increases exponentially. Therefore, the use of global stochastic optimizers became essential. Use of multi-objective optimizers such as MOSOMA (Multi-Objective Self-Organizing Migrating Algorithm) gives the user extra knowledge about the solved problem and its contradictory requirements. In this chapter, applications of MOSOMA for solution of problems from electromagnetics are first briefly reviewed. Then, three applications are discussed more in detail: design of Yagi-Uda antenna array, design of dielectric layered filter and control of adaptive beamforming in time domain of slotted antenna array. Results of MOSOMA are compared with previously published solutions. The possibility how to treat problems having discrete decision space is discussed here.