Comparison of Weighted Sum Fitness Functions for PSO Optimization of Wideband Medium-gain Antennas

In recent years PSO (Particle Swarm Optimization) has been successfully applied in antenna design. It is well-known that the cost function has to be carefully chosen in accordance with the requirements in order to reach an optimal result. In this paper, two different wideband medium-gain arrays are chosen as benchmark structures to test the performance of four PSO fitness functions that can be considered in such a design. The first one is a planar 3 element, the second one a linear 4 element antenna. A MoM (Method of Moments) solver is used in the design. The results clearly show that the fitness functions achieve a similar global best candidate structure. The fitness function based on realized gain however converges slightly faster than the others

Characteristics of different focusing antennas in the near field region

Focusing antennas are of interest in many application including microwave wireless power transmission, remote (non-contact) sensing, and medical applications. Different kinds of antennas such as array antennas, reflector antennas and Fresnel zone plate (FZP) antennas have been used for these applications. Here, first, a new scheme in designing focused array antennas with desired sidelobe levels (SLLs) in the near field region is presented. The performance of the large focused array antennas is predicted based on the knowledge of the mutual admittances of a smaller array. The effects of various focal distances on the near field pattern of these antennas are investigated. Then, electric field pattern characteristics of the focused Fresnel zone plate lens antennas in the near-field region are presented. The FZP antenna fed by a circular horn is implemented and the effects of various focal lengths on the near field pattern of this antenna are examined. It is shown that the maximum field intensity occurs closer to the antenna aperture than to the focal point and this displacement increases as the focal point moves away from the antenna aperture. The focusing properties of ultra-wideband (UWB) array antennas are also presented. Large current radiator (LCR) antennas are modeled by replacing the antenna with a set of infinitesimal dipoles producing the same near field of the antenna. LCR antenna arrays are used to provide high concentration of microwave power into a small region. It is shown that the defocusing effect occurs in pulse radiating antennas as well. Invasive weed optimization (IWO), a new optimization algorithm, is also employed to optimize the pulsed array antenna. In the attempt of optimizing the focused arrays, a new scenario for designing thinned array antennas using this optimization method is introduced. It is shown that by using this method, the number of elements in the array can be optimized, which yields a more efficient pattern with less number of elements. By applying this new optimization method to UWB arrays, the peak power delivered to a localized region can be increased

Automated design optimisation and simulation of stitched antennas for textile devices

This thesis describes a novel approach for designing 7-segment and 5-angle pocket and collar planar antennas (for operation at 900 MHz). The motivation for this work originates from the problem of security of children in rural Nigeria where there is risk of abduction. There is a strong potential benefit to be gained from hidden wireless tracking devices (and hence antennas) that can protect their security. An evolutionary method based on a genetic algorithm was used in conjunction with electromagnetic simulation. This method determines the segment length and angle between segments through several generations. The simulation of the antenna was implemented using heuristic crossover with non-uniform mutation. Antennas obtained from the algorithm were fabricated and measured to validate the proposed method.This first part of this research has been limited to linear wire antennas because of the wide range and flexibility of this class of antennas. Linear wire antennas are used for the design of high or low gain, broad or narrow band antennas. Wire antennas are easy and inexpensive to build. All the optimised linear wire antenna samples exhibit similar performances, most of the power is radiated within the GSM900 frequency band. The reflection coefficient (S11) is generally better than -10dB. The method of moment (MoM-NEC2) and FIT (CST Studio Suite 2015) solvers were used for this design. MATLAB is used to as an interface to control computational electromagnetic solvers for antenna designs and analysis. The genetic algorithm procedures were written in MATLAB. The second part of the work focuses on meshed ground planes for applications at 900 MHz global system for mobile communications (GSM), 2.45 GHz industrial, scientific, and medical (ISM) band and 5 GHz wearable wireless local area networks (WLAN) frequencies. Square ground planes were developed and designed using linear equations in MATLAB. The ground plane was stitched using embroidery machines. To examine the effect of meshing on the antenna performance and to normalise the meshed antenna to a reference, solid patch antenna was designed, fabricated on an FR4 substrate. A finite grid of resistors was created for numerical simulation in MATLAB. The resistance from the centre to any node of a finite grid of resistors are evaluated using nodal analysis. The probability that a node connects to each node in the grid was computed. The circuit model has been validated against the experimental model by measurement of the meshed ground plane. A set of measurement were collected from a meshed and compared with the numerical values, they show good agreement.</div

Bio-Inspired Optimization of Ultra-Wideband Patch Antennas Using Graphics Processing Unit Acceleration

Ultra-wideband (UWB) wireless systems have recently gained considerable attention as effective communications platforms with the properties of low power and high data rates. Applications of UWB such as wireless USB put size constraints on the antenna, however, which can be very dicult to meet using typical narrow band antenna designs. The aim of this thesis is to show how bio-inspired evolutionary optimization algorithms, in particular genetic algorithm (GA), particle swarm optimization (PSO) and biogeography-based optimization (BBO) can produce novel UWB planar patch antenna designs that meet a size constraint of a 10 mm 10 mm patch. Each potential antenna design is evaluated with the nite dierence time domain (FDTD) technique, which is accurate but time-consuming. Another aspect of this thesis is the modication of FDTD to run on a graphics processing unit (GPU) to obtain nearly a 20 speedup. With the combination of GA, PSO, BBO and GPU-accelerated FDTD, three novel antenna designs are produced that meet the size and bandwidth requirements applicable to UWB wireless USB system

Reconfigurable pixel antennas for communications

The explosive growth of wireless communications has brought new requirements in terms of compactness, mobility and multi-functionality that pushes antenna research. In this context, recon gurable antennas have gained a lot of attention due to their ability to adjust dynamically their frequency and radiation properties, providing multiple functionalities and being able to adapt themselves to a changing environment. A pixel antenna is a particular type of recon gurable antenna composed of a grid of metallic patches interconnected by RF-switches which can dynamically reshape its active surface. This capability provides pixel antennas with a recon guration level much higher than in other recon gurable architectures. Despite the outstanding recon guration capabilities of pixel antennas, there are important practical issues related to the performance-complexity balance that must be addressed before they can be implemented in commercial systems. This doctoral work focuses on the minimization of the pixel antenna complexity while maximizing its recon guration capabilities, contributing to the development of pixel antennas from a conceptual structure towards a practical recon gurable antenna architecture. First, the conceptualization of novel pixel geometries is addressed. It is shown that antenna complexity can be signi cantly reduced by using multiple-sized pixels. This multi-size technique allows to design pixel antennas with a number of switches one order of magnitude lower than in common pixel structures, while preserving high multiparameter recon gurability. A new conceptual architecture where the pixel surface acts as a parasitic layer is also proposed. The parasitic nature of the pixel layer leads to important advantages regarding the switch biasing and integration possibilities. Secondly, new pixel recon guration technologies are explored. After investigating the capabilities of semiconductors and RF-MEMS switches, micro uidic technology is proposed as a new technology to create and remove liquid metal pixels rather than interconnecting them. Thirdly, the full multi-parameter recon guration capabilities of pixel antennas is explored, which contrasts with the partial explorations available in the literature. The maximum achievable recon guration ranges (frequency range, beam-steering angular range and polarization modes) as well as the linkage between the di erent parameter under recon guration are studied. Finally, the performance of recon gurable antennas in beam-steering applications is analyzed. Figures-of-merit are derived to quantify radiation pattern recon gurability, enabling the evaluation of the performance of recon gurable antennas, pixel antennas and recon guration algorithms

Applications of the genetic algorithm optimisation approach in the design of high efficiency microwave class E power amplifiers

In this thesis Genetic Algorithm Optimisation Methods (GA) is studied and for the first time used to design high efficiency microwave class E power amplifiers (PAs) and associated load patch antennas. The difficulties of designing high efficiency PAs is that power transistors are highly non linear and classical design techniques only work for resistive loads. There are currently no high efficient and accurate procedures for design high efficiency PAs. To achieve simplified and accurate design procedure, GA and new design quadratic equations are introduced and applied. The performance analysis is based on linear switch models and non linear circuitry push-pull methods. The results of the analytical calculations and experimental verification showed that the power added efficiency (PAE) of the PAs mainly depend on the losses of the active device itself and are nearly independent on the losses of its harmonic networks. Hence, it has been proven that the cheap material PCB FR4 can be used to design high efficiency class E PAs and it also shown that low Q factor networks have only a minor effect on efficiency, allowing a wide bandwidth to be obtained. In additional, a new procedure for designing class E PAs is introduced and applied. The active device (ATF 34143) is used. Good agreement was obtained between predicted analyses and the simulation results (from Microwave Office (AWR) and Agilent ADS software). For the practical realization, class E PAs were fabricated and tested using PCB FR4. The practical results validate computer simulations and the PAE of the class E PAs are more than 71% and Gain is over 3.8 dB when input power (Pin) is equal to 14 dBm at 2 GHz

Reconfigurable pixel antennas for communications

Premi extraordinari doctorat curs 2012-2013, àmbit Enginyeria de les TICThe explosive growth of wireless communications has brought new requirements in terms of compactness, mobility and multi-functionality that pushes antenna research. In this context, recon gurable antennas have gained a lot of attention due to their ability to adjust dynamically their frequency and radiation properties, providing multiple functionalities and being able to adapt themselves to a changing environment. A pixel antenna is a particular type of recon gurable antenna composed of a grid of metallic patches interconnected by RF-switches which can dynamically reshape its active surface. This capability provides pixel antennas with a recon guration level much higher than in other recon gurable architectures. Despite the outstanding recon guration capabilities of pixel antennas, there are important practical issues related to the performance-complexity balance that must be addressed before they can be implemented in commercial systems. This doctoral work focuses on the minimization of the pixel antenna complexity while maximizing its recon guration capabilities, contributing to the development of pixel antennas from a conceptual structure towards a practical recon gurable antenna architecture. First, the conceptualization of novel pixel geometries is addressed. It is shown that antenna complexity can be signi cantly reduced by using multiple-sized pixels. This multi-size technique allows to design pixel antennas with a number of switches one order of magnitude lower than in common pixel structures, while preserving high multiparameter recon gurability. A new conceptual architecture where the pixel surface acts as a parasitic layer is also proposed. The parasitic nature of the pixel layer leads to important advantages regarding the switch biasing and integration possibilities. Secondly, new pixel recon guration technologies are explored. After investigating the capabilities of semiconductors and RF-MEMS switches, micro uidic technology is proposed as a new technology to create and remove liquid metal pixels rather than interconnecting them. Thirdly, the full multi-parameter recon guration capabilities of pixel antennas is explored, which contrasts with the partial explorations available in the literature. The maximum achievable recon guration ranges (frequency range, beam-steering angular range and polarization modes) as well as the linkage between the di erent parameter under recon guration are studied. Finally, the performance of recon gurable antennas in beam-steering applications is analyzed. Figures-of-merit are derived to quantify radiation pattern recon gurability, enabling the evaluation of the performance of recon gurable antennas, pixel antennas and recon guration algorithms.Award-winningPostprint (published version

Doctor of Philosophy

dissertationThree-dimensional (3D) rapid prototyping holds significant promise for future antenna designs. Many complex designs that would be unmanufacturable or costly are realizable on a 3D printing machine. The ability to create 3D designs of virtually any configuration makes it possible to build compact antennas that can form fit to any space. These antennas build on the concept that small antennas can best reach the ideal operating limit when utilizing the entire 3D space in a sphere surrounding the antenna. Antennas require a combination of dielectric and conductive materials. 3D rapid prototyping is already well advanced for plastics and dielectric materials (with more options coming online). Prototyping with conductive materials has lagged behind; due mainly to their higher melting points, but this is advancing as well. This dissertation focuses on 3D rapid prototyping for antenna design. A 3D antenna made from small cubical cells is optimized for 2.4-3GHz using a genetic algorithm (GA). The antennas are built using 3D printing of plastic covered by conductive paint. The effects of the conductivity of the paint and number of layers on the resonance and gain of the antenna are evaluated. These results demonstrate the feasibility of using 3D rapid prototyping for antenna design