An algorithm for calculating Green's functions of planar, circular cylindrical and spherical multilayer substrates

We propose Multi-Strategy Coevolving Aging Particles (MS-CAP), a novel population-based algorithm for black-box optimization. In a memetic fashion, MS-CAP combines two components with complementary algorithm logics. In the first stage, each particle is perturbed independently along each dimension with a progressively shrinking (decaying) radius, and attracted towards the current best solution with an increasing force. In the second phase, the particles are mutated and recombined according to a multi-strategy approach in the fashion of the ensemble of mutation strategies in Differential Evolution. The proposed algorithm is tested, at different dimensionalities, on two complete black-box optimization benchmarks proposed at the Congress on Evolutionary Computation 2010 and 2013. To demonstrate the applicability of the approach, we also test MS-CAP to train a Feedforward Neural Network modelling the kinematics of an 8-link robot manipulator. The numerical results show that MS-CAP, for the setting considered in this study, tends to outperform the state-of-the-art optimization algorithms on a large set of problems, thus resulting in a robust and versatile optimizer.

Multi-Strategy Coevolving Aging Particle Optimization

MATLAB handbook for the textbook Foundations of Antennas - A unified approach

The capability of non-planar adaptive antennas for suppressing interference in GPS applications is addressed. An optimization problem based on power minimization of incident signals is formulated, resulting in a solution that maximizes the signal-to-interference-plus-noise ratio at the output of the antenna array and subsequently the carrier-to-noise-ratio of a GPS satellite signal. Spherical adaptations of a planar seven element controlled reception pattern antenna array are presented for various low-horizon interference environments.

Spherical Cap Adaptive Antennas for GPS

Dimension Optimization of Microstrip Patch Antenna in X/Ku Band via Artificial Neural Network☆

In this paper, the input impedance and radiation pattern of spherical rectangular patch antennas are studied. The electric field integral equation is numerically solved by applying the method of moments where the multilayer spherical structure is rigorously considered, using the spectral-domain algorithm for calculating Green's functions. In order to avoid numerical problems, a modified vector–Legendre transformation and normalized Legendre polynomials are defined and applied to the solution procedure. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 276–280, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10741

Analysis of rectangular microstrip patch antennas on spherical structures

Microstrip antennas became very attractive due to their features like small dimensions, simplicity, conformability and low cost of production. The production these antennas for wireless communication is focused to design efficient, wide band, antennas that easily can be incorporated into various systems. Design parameters of microstrip antenna need to be calculated in very high accuracy to ensure proper functioning. Design of the rectangular or circular microstrip patch antenna requires high accuracy of calculations, and it is not so easy task. The known models (transmission line model or cavity model) give less accurate results. Simulations based on full-wave analysis techniques, such as CST Studio SuiteTM, enable more accurate analysis of microstrip antenna characteristics, but they suffer from time consuming, intensive computations. Demand for fast and enough accurate computations can be satisfied using neural network models. This work studies microstrip patch antenna design using artificial neural network optimized by PSO (Particle Swarm Optimization) algorithm. According to neural network design results an antenna was made. The calculated and neural network results are compared with measured antenna values.

Microstrip antenna design using neural networks optimized by PSO

Arrays of rectangular single- and stacked-patch antennas embedded in a multilayer spherical structure are analysed using the spectral-domain approach and the moment method. The patch current is transformed to the spectral domain using the vector-Legendre transformation. This simplifies the analysis procedure, because the electromagnetic field excited by one spectral source component has the same angular variation as the source. To avoid numerical difficulties appearing when analysing structures with large radii, a modified vector-Legendre transformation and normalised Legendre functions are defined and applied to the solution procedure. Furthermore, the asymptotic formulas for the field distribution of higher-order spectral modes are implemented into the algorithm for calculating Green's functions. The effect of deviation from the spherical symmetry and the influence of the structure radius on self and mutual impedance are studied. A laboratory model is built to test different configurations of spherical patch antennas and to validate the developed program.

Analysis of spherical arrays of microstrip antennas using moment method in spectral domain

A rigorous mathematical analysis is given of spherical stacked-patch arrays with emphasis on the physical interpretation of mutual coupling mechanisms present in doubly- curved convex structures. The analysis method is based on electromagnetic field representation in terms of spherical harmonics where each harmonic has the same angular variation as the spectral source component. To obtain the spectral representation the vector-Legendre transformation is applied to currents and fields. A novel approach to the mutual coupling calculation within the method of moments analysis of spherical arrays is applied. By expressing the patch current in terms of two suitable potential-like auxiliary functions, it is possible to avoid the use of Euler's formulas for coordinate system rotation and the related lengthy integrations. Instead, the rotation of antenna elements and corresponding current distributions can be done in closed form with the help of Vilenkin's addition theorem for associated Legendre functions. It is shown that the new approach results in significant acceleration and improved accuracy of the analysis of spherical patch antenna arrays. The algorithm is successfully tested against a commercially available electromagnetic software and measurements performed on the developed laboratory model, confirming its accuracy for both input impedance and mutual coupling calculation and with only a small difference between the predicted and measured resonant frequencies, due to limitations in the experimental model. The influence of the structure parameters on mutual coupling level is extensively investigated, including all coupling mechanisms and leakage of energy due to curvature of the structure. It is shown that stacked-patch antennas can have reduced coupling level comparing to single patch antennas with possible deep nulls above the antenna resonant frequency.

Niksa Burum

Papers

Analysis of rectangular microstrip patch antennas on spherical structures

Microstrip antenna design using neural networks optimized by PSO

Analysis of spherical arrays of microstrip antennas using moment method in spectral domain

Study of Mutual Coupling Between Circular Stacked-Patch Antennas on a Sphere

Analysis of spherical arrays of microstrip antennas using moment method in spectral domain