Design Optimization Of Antennas Research Articles

Fast Multiobjective Optimization of Narrowband Antennas Using RSA Models and Design Space Reduction

A computationally efficient technique for multiobjective design optimization of narrowband antennas is presented. In our approach, the corrected low-fidelity antenna model [obtained through coarse-discretization electromagnetic (EM) simulations] is enhanced using frequency scaling and response correction, sampled, and utilized to obtain a fast response surface approximation (RSA) antenna surrogate. The RSA model is constructed in the reduced design space. The initial set of Pareto-optimal designs is then utilized to confine the design space further by identifying designs that satisfy minimum requirements with respect to antenna reflection response. The updated RSA model set up in the confined space is subsequently optimized to yield the final Pareto set at the low computational cost.

A Building-Block Favoring Method for the Topology Optimization of Internal Antenna Design

This paper proposes a new design technique for internal antenna development. The proposed method is based on the framework of topology optimization incorporated with three effective mechanisms favoring the building blocks of associated optimization problems. Conventionally, the topology optimization of antenna structures discretizes a design space into uniform and rectangular pixels. However, the defining length of the resultant building blocks is so large that the problem difficulty arises; furthermore, the order of the building blocks becomes extremely high, so genetic algorithms (GAs) and binary particle swarm optimization (BPSO) are not more efficient than the random search algorithm. In order to form tight linkage groups of building blocks, this paper proposes a novel approach to handle the design details. In particular, a nonuniform discretization is adopted to discretize the design space, and the initialization of GAs is assigned as orthogonal arrays (OAs) instead of a randomized population; moreover, the control map of GAs is constructed by ensuring the schema growth based on the generalized schema theorem. By using the proposed method, two internal antennas are thus successfully developed. The simulated and measured results show that the proposed technique significantly outperforms the conventional topology optimization.

A compact microwave patch applicator for hyperthermia treatment of cancer.

Design and development of a compact microstrip C-type patch applicator for hyperthermia treatment of cancer is presented. The patch antenna is optimized for resonance at 434 MHz, return loss (S11) better than -15dB and co-polarized electric field in tissue. Effect of water bolus thickness on power delivery is studied for improved power coupling. Numerical simulations for antenna design optimization carried out using EM simulation software, Ansys HFSS(®), USA were experimentally verified. The effective field coverage for the optimized patch antenna and experimental results indicate that the compact antenna resonates at ISM frequency 434 MHz with better than -15 dB power coupling.

A Semi-Analytical Solution of a Tapered Half-Mode Substrate-Integrated Waveguide With Application to Rapid Antenna Optimization

A semi-analytical solution for the input reflections, inner field distribution and radiated fields for a wideband traveling-wave antenna based on a tapered half-mode substrate-integrated waveguide (HMSIW) is proposed in this paper. The analysis validates the operation mechanism for this type of traveling-wave antenna which exhibits omni-directional radiation properties with horizontal polarization (“magnetic dipole”). The derived expressions allows the design and efficient optimization of different antennas towards fulfilling various predefined specifications of reflection coefficient and operating bandwidth. The antenna utilizes a wideband transition from coaxial cable to a HMSIW, which is also considered in the model to provide highly accurate semi-analytical results. Utilizing the proposed method, three antennas of different specifications have been optimized, manufactured and tested. The analysis, simulation and measurement results show good correspondences, which verifies the design process and demonstrates the versatility of the concept.

Design optimisation of antennas using electromagnetic simulations and adaptive response correction technique

In this study, the authors describe a simple and reliable procedure for electromagnetic (EM) simulation-based design of antennas. The authors' approach exploits coarse-discretisation EM simulations (the low-fidelity antenna model) and the adaptive response correction (ARC) technique. ARC is used to enhance the low-fidelity model response so that it can serve as a cheap yet accurate representation of the high-fidelity EM model of the antenna under design. The ARC-based iterative correction-prediction process yields an optimised design at a low CPU cost corresponding to a few high-fidelity simulations of the antenna. The proposed approach is compared with direct optimisation of the high-fidelity model and to surrogate-based optimisation exploiting output space mapping. The results obtained for two antenna design cases indicate by reduction of the overall design cost that ARC allows for better utilisation of the knowledge embedded in the low-fidelity model than the simpler correction method.

An Investigation Into the Gustafsson Limit for Small Planar Antennas Using Optimization

The fundamental limit for small antennas provides a guide to the effectiveness of designs. Gustafsson et al, Yaghjian et al, and Mohammadpour-Aghdam et al independently deduced a variation of the Chu-Harrington limit for planar antennas in different forms. Using a multi-parameter optimisation technique based on the ant colony algorithm, planar, meander dipole antenna designs were selected on the basis of lowest resonant frequency and maximum radiation efficiency. The optimal antenna designs across the spectrum from 570 to 1750 MHz occupying an area of $56mm \times 25mm$ were compared with these limits calculated using the polarizability tensor. The results were compared with Sievenpiper's comparison of published planar antenna properties. The optimised antennas have greater than 90% polarizability compared to the containing conductive box in the range $0.3<ka<1.1$, so verifying the optimisation algorithm. The generalized absorption efficiency of the small meander line antennas is less than 50%, and results are the same for both PEC and copper designs.

Optimal Antenna Design With QPSO–QN Optimization Strategy

A new optimization strategy with the ability of global searching and rapid convergence is proposed for optimal antenna design with multiple parameters. The strategy combines the quantum-behaved particle swarm optimization (QPSO) algorithm with the quasi-Newton (QN) method. The QN is employed after QPSO in order to overcome the premature and to achieve a higher accuracy. The method is demonstrated by optimizing a circularly polarized microstrip antenna with five parameters.

An Efficient Method for Antenna Design Optimization Based on Evolutionary Computation and Machine Learning Techniques

In recent years, various methods from the evolutionary computation (EC) field have been applied to electromagnetic (EM) design problems and have shown promising results. However, due to the high computational cost of the EM simulations, the efficiency of directly using evolutionary algorithms is often very low (e.g., several weeks' optimization time), which limits the application of these methods for many industrial applications. To address this problem, a new method, called surrogate model assisted differential evolution for antenna synthesis (SADEA), is presented in this paper. The key ideas are: (1) A Gaussian Process (GP) surrogate model is constructed on-line to predict the performances of the candidate designs, saving a lot of computationally expensive EM simulations. (2) A novel surrogate model-aware evolutionary search mechanism is proposed, directing effective global search even when a traditional high-quality surrogate model is not available. Three complex antennas and two mathematical benchmark problems are selected as examples. Compared with the widely used differential evolution and particle swarm optimization, SADEA can obtain comparable results, but achieves a 3 to 7 times speed enhancement for antenna design optimization.

Phase Characterization of Reconfigurable Reflectarray Antennas

The design and performance optimization of X-band reconfigurable reflectarray antennas have been discussed in this paper concentrating mainly on the phase characteristics. Liquid crystals based substrates and slot embedded patch elements have been proposed as two different techniques for the design of reflectarrays with frequency tunability characteristics. Reflectarray patch elements constructed on anisotropic liquid crystal substrate are proposed to be employed as a dynamic phase control strategy for terrestrial systems. A detailed analysis of dynamic phase range and frequency tunability with respect to dielectric anisotropy is presented for two different anisotropic liquid crystal substrate materials. The investigated liquid crystals substrates provided a maximum reduction of 14.1% in volume for reflectarray design at 10 GHz. Moreover rectangular slots on the patch elements are shown to offer a maximum frequency tenability of 1.7GHz. The Finite Integral Method (FIM) validated by waveguide scattering parameter measurements demonstrated a dynamic phase range of 314° and a volume reduction of up to 24.36%.

Rapid optimisation of omnidirectional antennas using adaptively adjusted design specifications and kriging surrogates

A methodology for rapid design optimisation of omnidirectional antennas is presented. In order to reduce the computational cost of the geometry parameter adjustment process the authors exploit coarse discretisation electromagnetic (EM) simulations of the antenna structure under consideration as its low-fidelity model. A fast response surface approximation (RSA) model of the sampled EM data is created using kriging interpolation. The RSA model is subsequently used in the surrogate-based design process with the adaptively adjusted design specification (AADS) technique utilised as the optimisation engine. AADS allows us to account for the discrepancy between the surrogate and the high-fidelity EM antenna model. The optimised designs can be obtained at a low computational cost corresponding to a few evaluations of the high-fidelity antenna model as demonstrated through examples. Comparison with the benchmark technique indicates that using the RSA surrogates results in substantial reduction of the overall optimisation cost.

Multipoint Response Correction for Reduced‐Cost EM‐Simulation‐Driven Design of Antenna Structures

ABSTRACTWe present a simple technique for electromagnetic (EM) simulation–based design optimization of antenna structures. Our approach utilizes a low‐fidelity model of the antenna under design, implemented through coarse‐discretization EM simulations. The low‐fidelity model is aligned with the original, high‐fidelity one using multipoint response correction. As opposed to the simple additive response correction (referred to as output space mapping), the multipoint version introduced here exploits all high‐fidelity model data accumulated during the optimization process, which improves the generalization capability of the corrected model. As a result, an optimized antenna design can be obtained at a lower computational cost, which is demonstrated using two examples: a dielectric resonator antenna and an ultra‐wideband stripline monopole antenna. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2070–2074, 2013

Roll-to-Roll Screen Printed Radio Frequency Identification Transponder Antennas for Vehicle Tracking Systems

Vehicle tracking systems based on ultra high frequency (UHF) radio frequency identification (RFID) technology are already introduced to control the access to car parks and corporate premises. For this field of application so-called Windshield RFID transponder labels are used, which are applied to the inside of the windshield. State of the art for manufacturing these transponder antennas is the traditional lithography/etching approach. Furthermore the performance of these transponders is limited to a reading distance of approximately 5 m which results in car speed limit of 5 km/h for identification. However, to achieve improved performance compared to existing all-purpose transponders and a dramatic cost reduction, an optimized antenna design is needed which takes into account the special dielectric and in particular metallic car environment of the tag and an roll-to-roll (R2R) printing manufacturing process. In this paper we focus on the development of a customized UHF RFID transponder antenna design, which is adopted for vehicle geometry as well as R2R screen printing manufacturing processes.

RF sheath-enhanced beryllium sources at JET’s ICRH antennas

Local beryllium (Be) I and Be II line intensities were measured in the plasma–wall interaction region near an ICRH antenna in JET. The intent was to use these intensities as a measure of the formation of local Radio Frequency (RF) sheath potentials, through RF sheath rectification and potential build up at the end of field lines passing in front of the antenna. Experimentally, it was found that the Be I and Be II emission increase when using the antenna local to the spectroscopic measurement, and increase even more when using a remote antenna that is magnetically connected to the observation point. Magnetic field mapping indicates a magnetic connection between the observation location and the top corner region of the remote antenna and/or its protection limiter. These measurements can be used in support of RF sheath modeling that is an important part of the optimization of antenna design for next generation fusion energy devices, including ITER.

Application of genetic algorithm to the optimization of resonant frequency of coaxially fed rectangular microstrip antenna

Microstrip antenna is gathering a lot of interest in communication systems. Genetic algorithm is a popular optimization technique and has been introduced for design optimization of microstrip patch antenna. In this paper, genetic algorithm has been used for optimization of resonant frequency of coaxially fed rectangular microstrip antenna. The investigation is made at 3 different frequencies 3GHz, 5GHz and 10GHz respectively. Patch length, patch width & feed position are taken as optimization parameters. Return loss and radiation pattern for the optimized antenna are verified using IE3D software. Accuracy of the results encourages the use of genetic algorithm. Keywords - Rectangular microstrip antenna, genetic algorithm, resonant frequency, IE3D.

Shape-Preserving Response Prediction for Engineering Design Optimization

Contemporary engineering design relies heavily on computer simulations. The structures and systems considered in many engineering disciplines are far too complex to be described accurately using simple theoretical models; using simulations is often the only way to adequately assess the performance of the design. Unfortunately, high-fidelity simulations are computationally expensive so that their use in an automated design process based on conventional optimization algorithms is often prohibitive. Despite the availability of faster computers and more efficient simulation software: growing demand for improved accuracy and the need to evaluate larger and larger systems effectively diminishes the benefits of this increase in computing power. One of the most promising ways of alleviating these problems are surrogate-based optimization (SBO) techniques which are capable of reducing the number of expensive objective function evaluations in a simulation-driven design process. In SBO, the direct optimization of the expensive model is replaced by iterative updating and re-optimization of its cheap surrogate model. Among proven SBO techniques, the methods exploiting physics-based low-fidelity models are probably the most efficient. This is because the knowledge about the system of interest embedded in the low-fidelity model allows constructing the surrogate model that has good generalization capability at a cost of just a few evaluations of the original model. In this paper, we review one of the most recent techniques of this kind, the so-called shape-preserving response prediction (SPRP). We discuss the formulation of SPRP, its limitations and generalizations, and, most importantly, demonstrate its applications to solve design problems in various engineering areas, including microwave engineering, antenna design, and aerodynamic shape optimization.

Cost-efficient electromagnetic-simulation-driven antenna design using co-Kriging

A technique for design optimisation of antennas is presented. The approach exploits coarse-discretisation electromagnetic (EM) simulations of the antenna of interest that are used to create its fast initial model (a surrogate) through Kriging. During the design process, predictions obtained by optimising the surrogate are verified using high-fidelity EM simulations, and these high-fidelity data are used to enhance the surrogate using co-Kriging interpolation that accommodates all EM simulation data into one surrogate model. The co-Kriging-based optimisation algorithm is simple and it is capable of yielding a satisfactory design at a low-cost equivalent to a few high-fidelity EM simulations of the antenna under design. To the best of author&apos;s knowledge, this is a first application of co-Kriging to antenna design. The proposed approach is demonstrated using several antenna design cases and compared with other techniques including pattern search and space mapping.

Evolutionary Optimization of Optical Antennas

The design of nanoantennas has so far been mainly inspired by radio-frequency technology. However, the material properties and experimental settings need to be reconsidered at optical frequencies, which would entail the need for alternative optimal antenna designs. Here we subject a checkerboard-type, initially random array of gold cubes to evolutionary optimization. To illustrate the power of the approach, we demonstrate that by optimizing the near-field intensity enhancement, the evolutionary algorithm finds a new antenna geometry, essentially a split-ring-two-wire antenna hybrid that surpasses by far the performance of a conventional gap antenna by shifting the n=1 split-ring resonance into the optical regime.

Reduced‐cost design optimization of antenna structures using adjoint sensitivity

AbstractWe discuss a simple and yet robust algorithm for electromagnetic (EM) simulation‐driven design optimization of antennas. Our procedure exploits adjoint sensitivities to obtain gradient information without extra EM simulations as well as adaptive algorithm that adjusts the search radius for optimizing the linear model of the antenna. The proposed technique is capable of yielding an optimized antenna design at a much lower computational cost than a benchmark algorithm, Matlab's fminimax, also using adjoint sensitivities. Our approach is demonstrated using two antenna design cases: a planar inverted‐F antenna and a wideband hybrid antenna. The design time savings are between 60 and 75% with respect to the benchmark method. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:2594–2597, 2012; this online at wileyonlinelibrary.com. DOI 10.1002/mop.27112

Miniature microwave applicator for murine bladder hyperthermia studies

Purpose: Novel combinations of heat with chemotherapeutic agents are often studied in murine tumour models. Currently, no device exists to selectively heat small tumours at depth in mice. In this project we modelled, built and tested a miniature microwave heat applicator, the physical dimensions of which can be scaled to adjust the volume and depth of heating to focus on the tumour volume. Of particular interest is a device that can selectively heat murine bladder.Materials and methods: Using Avizo® segmentation software, we created a numerical mouse model based on micro-MRI scan data. The model was imported into HFSS™ (Ansys) simulation software and parametric studies were performed to optimise the dimensions of a water-loaded circular waveguide for selective power deposition inside a 0.15 mL bladder. A working prototype was constructed operating at 2.45 GHz. Heating performance was characterised by mapping fibre-optic temperature sensors along catheters inserted at depths of 0–1 mm (subcutaneous), 2–3 mm (vaginal), and 4–5 mm (rectal) below the abdominal wall, with the mid depth catheter adjacent to the bladder. Core temperature was monitored orally.Results: Thermal measurements confirm the simulations which demonstrate that this applicator can provide local heating at depth in small animals. Measured temperatures in murine pelvis show well-localised bladder heating to 42–43°C while maintaining normothermic skin and core temperatures.Conclusions: Simulation techniques facilitate the design optimisation of microwave antennas for use in pre-clinical applications such as localised tumour heating in small animals. Laboratory measurements demonstrate the effectiveness of a new miniature water-coupled microwave applicator for localised heating of murine bladder.

Rapid antenna design optimization using shape-preserving response prediction

Rapid antenna design optimization using shape-preserving response prediction An approach to rapid optimization of antennas using the shape-preserving response-prediction (SPRP) technique and coarse-discretization electromagnetic (EM) simulations (as a low-fidelity model) is presented. SPRP allows us to estimate the response of the high-fidelity EM antenna model, e.g., its reflection coefficient versus frequency, using the properly selected set of so-called characteristic points of the low-fidelity model response. The low-fidelity model, corrected by means of SPRP, is subsequently used to predict the optimal design. The design process is cost efficient because most operations are performed on the low-fidelity model. Performance of our technique is demonstrated using a dielectric resonator antenna and two planar wideband antenna examples. In all cases, the optimal design is obtained at a cost corresponding to a few high-fidelity simulations of the antenna under design.