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Topology Optimisation of Wideband Coaxial-to-Waveguide Transitions
Umeå University, Faculty of Science and Technology, Department of Computing Science. Department of electronics and electrical communications, Menoufia University, Menouf, 32952, Egypt.ORCID iD: 0000-0002-1318-7519
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science.
Umeå University, Faculty of Science and Technology, Department of Computing Science.ORCID iD: 0000-0003-0473-3263
2017 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, 45110Article in journal (Refereed) Published
Abstract [en]

To maximize the matching between a coaxial cable and rectangular waveguides, we present a computational topology optimisation approach that decides for each point in a given domain whether to hold a good conductor or a good dielectric. The conductivity is determined by a gradient-based optimisation method that relies on finite-difference time-domain solutions to the 3D Maxwell’s equations. Unlike previously reported results in the literature for this kind of problems, our design algorithm can efficiently handle tens of thousands of design variables that can allow novel conceptual waveguide designs. We demonstrate the effectiveness of the approach by presenting optimised transitions with reflection coefficients lower than −15dB over more than a 60% bandwidth, both for right-angle and end-launcher configurations. The performance of the proposed transitions is crossverified with a commercial software, and one design case is validated experimentally.

Place, publisher, year, edition, pages
2017. Vol. 7, 45110
Keyword [en]
topology optimization, finite-difference time- domain (FDTD), adjoint-field problem, waveguides, coaxial cable, transitions design, end-launcher.
National Category
Computer Science
Identifiers
URN: urn:nbn:se:umu:diva-102577DOI: 10.1038/srep45110ISI: 000397137700001OAI: oai:DiVA.org:umu-102577DiVA: diva2:808372
Funder
Swedish Research Council, 621-2013-3706
Available from: 2015-04-28 Created: 2015-04-28 Last updated: 2017-05-12Bibliographically approved
In thesis
1. Topology Optimization of Antennas and Waveguide Transitions
Open this publication in new window or tab >>Topology Optimization of Antennas and Waveguide Transitions
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis introduces a topology optimization approach to design, from scratch, efficient microwave devices, such as antennas and waveguide transitions. The design of these devices is formulated as a general optimization problem that aims to build the whole layout of the device in order to extremize a chosen objective function. The objective function quantifies some required performance and is evaluated using numerical solutions to the 3D~Maxwell's equations by the finite-difference time-domain (FDTD) method. The design variables are the local conductivity at each Yee~edge in a given design domain, and a gradient-based optimization method is used to solve the optimization problem. In all design problems, objective function gradients are computed based on solutions to adjoint-field problems, which are also FDTD discretization of Maxwell's equations but solved with different source excitations. For any number of design variables, the computation of the objective function gradient requires one solution to the original field problem and one solution to the associated adjoint-field problem. The optimization problem is solved iteratively using the globally convergent Method of Moving Asymptotes (GCMMA).

By the proposed approach, various design problems, including tens of thousands of design variables, are formulated and solved in a few hundred iterations. Examples of solved design problems are the design of wideband antennas, dual-band microstrip antennas, wideband directive antennas, and wideband coaxial-to-waveguide transitions. The fact that the proposed approach allows a fine-grained control over the whole layout of such devices results in novel devices with favourable performance. The optimization results are successfully verified with a commercial software package. Moreover, some devices are fabricated and their performance is successfully validated by experiments.

Place, publisher, year, edition, pages
Umeå University: Umeå University, 2015. 29 p.
Keyword
Maxwell's equations, topology optimization, antennas, waveguide transition, finite-difference time-domain, gradient-based optimization, adjoint-field problem, microwave devices.
National Category
Computer Science
Research subject
Computing Science
Identifiers
urn:nbn:se:umu:diva-102505 (URN)978-91-7601-255-0 (ISBN)
Public defence
2015-05-26, Naturvetarhuset, N450, Umeå universitet, Umeå, 10:15 (English)
Opponent
Supervisors
Available from: 2015-05-05 Created: 2015-04-27 Last updated: 2017-04-11Bibliographically approved

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