Kerim Guney

Optimal synthesis of linear antenna arrays using a harmony search algorithm

A method based on harmony search algorithm (HSA) for the pattern synthesis of linear antenna arrays with the prescribed nulls is presented. Nulling of the pattern is achieved by controlling the amplitude-only, the phase-only, and the position-only. The HSA is conceptualized using the musical process of searching for a perfect state of harmony. To show the effectiveness of the proposed HSA, several examples of linear antenna array patterns with the imposed single, multiple and broad nulls are given. It is found that the nulling method based on HSA is capable of steering the array nulls precisely to the undesired interference directions. The results of HSA are compared with the results of the modified touring ant colony optimization (MTACO), the bees algorithm (BA), the bacterial foraging algorithm (BFA), the plant growth simulation algorithm (PGSA), the clonal selection algorithm (CLONALG), the particle swarm optimization (PSO), the quadratic programming method (QPM), the tabu search algorithm (TSA), the genetic algorithm (GA), the memetic algorithm (MA), the nondominated sorting genetic algorithm 2 (NSGA-2), the multiobjective differential evolution (MODE), and the multiobjective evolutionary algorithms based on decomposition with differential evolution (MOEA/D-DE).

Bacterial Foraging Algorithm for Null Synthesizing of Linear Antenna Arrays by Controlling Only the Element Positions

A method based on the bacterial foraging algorithm (BFA) for the pattern synthesis of linear antenna arrays with the prescribed nulls is presented. Nulling of the pattern is achieved by controlling only the element positions. The BFA is a new evolutionary computing technique, based on the foraging behavior of Escherichia (E) coli bacteria in a human intestine. Simulation results for Chebyshev patterns with the imposed single, multiple and broad nulls are given to show the effectiveness of the proposed method. For practical consideration, due to small variations of the element positions, the sensitivity of the produced patterns is also examined by rounding the element position values to the second decimal position.

Null Synthesis of Time-Modulated Circular Antenna Arrays Using an Improved Differential Evolution Algorithm

An efficient variant of differential evolution (DE) algorithm, namely subpopulated differential evolution (subDE), is proposed for solving null synthesis problems of time-modulated circular antenna arrays by controlling time intervals and phases. The capabilities of subDE algorithm are examined by comparing its convergence curves and number of successful optimizations to those of the classical DE. Wilcoxon rank-sum test is also applied to ensure that the results are significant in terms of statistics. Furthermore, the antenna array parameters achieved by using subDE are compared to those of the classical DE in the literature. The results show that subDE can exhibit better performance than the classical DE for our antenna array synthesis examples. Additionally, the simulations are executed on an embedded microprocessor to investigate if subDE can also run on such a limited environment. The results demonstrate that the contemporary embedded systems hold promise for evolutionary algorithms.

Linear Antenna Array Synthesis Using Mean Variance Mapping Method

Abstract A mean variance mapping optimization algorithm for three types of antenna array synthesis examples is presented. Mean variance mapping optimization is based on the strategic transformation used for mutating the offspring built on mean variance of a certain dynamic population. The first set of examples is based on side-lobe suppression and null control by controlling element positions with mean variance mapping optimization under constraints to beam width. In the second group of examples, mean variance mapping optimization becomes an optimization tool to calculate the amplitude and phase values of antenna array elements to synthesize shaped beams. In the last set of examples, mean variance mapping optimization is used to mitigate the effect of failure elements on the pattern by recalculating the amplitude values of remaining elements. Additionally, a modification that provides a good balance between exploitation and exploration is applied to the mean variance mapping optimization algorithm to improve its stability and accuracy. The simulation results showed that the proposed mean variance mapping optimization is an effective and easy implementable technique for different antenna array synthesis problems.

Effective side length formula for resonant frequency of equilateral triangular microstrip antenna

A novel and accurate expression is obtained by employing the differential evolution algorithm for the effective side length (ESL) of the equilateral triangular microstrip antenna (ETMA). This useful formula allows the antenna engineers to accurately calculate the ESL of the ETMA. The computed resonant frequencies (RFs) show very good agreement with the experimental RFs when this accurate ESL formula is utilised for the computation of the RFs for the first five modes.

Recognition of Sleep Spindle using Artificial Neural Networks and Morphological Filter

Derin uyku doneminde gorulen uyku igcikleri, kaliteli bir uykunun belirtecidir. Uyku igcikleri, derin uykunun NREM2 evresinde siklikla gorulen kisa sureli olaylardan birisidir. Bu igcikleri, EEG isaretlerinde gorulen yuksek frekansli ve dusuk genlikli bilesenlerdir. Yapilan calismada, yapay sinir aglari kullanilarak uyku sirasinda EEG isaretinin NREM2 evresinde uyku igcikleri belirlenmeye calisilmistir. EEG isaretlerindeki uyku igcikleri, bir uzman tarafindan gorsel olarak isaretlenmistir. Bu calismada, EEG isaretleri yapay sinir agi ile islenmis, ag cikisinin iyilestirilmesi icin morfolojik filtre kullanilmis, elde edilen cikis isareti skorlama islemine tabi tutulmustur. Calismada Sekiz farkli insandan kaydedilen EEG isaretleri kullanilmistir. Bu isaretlerdeki 354 tane isaretlenen uyku igciginden 248 tanesi dogru olarak tespit edilmistir. Yapilan calismanin, Uzman sistemler kullanilarak yapilan uyku skorlamalarinda NREM2 evresinin skorlama basarisini artiracagi dusunulmektedir.