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Expedite Design of Variable-Topology Broadband Hybrid Couplers for Size Reduction Using Surrogate-Based Optimization and Co-Simulation Coarse Models
(2017) Kurgan, Piotr; Koziel, Slawomir; Leifsson, Leifur; Du, Xiaosong; Department of Engineering
In this paper, we discuss a computationally efficient approach to expedite design optimization of broadband hybrid couplers occupying a minimized substrate area. Structure size reduction is achieved here by decomposing an original coupler circuit into low- and high-impedance components and replacing them with electrically equivalent slow-wave lines with reduced physical dimensions. The main challenge is reliable design of computationally demanding low-impedance slow-wave structures that feature a quasi-periodic circuit topology for wideband operation. Our goal is to determine an adequate number of recurrent unit elements as well as to adjust their designable parameters so that the coupler footprint area is minimal. The proposed method involves using surrogate-based optimization with a reconfigurable co-simulation coarse model as the key component enabling design process acceleration. The latter model is composed in Keysight ADS circuit simulator from multiple EM-evaluated data blocks of the slow-wave unit element and theory-based feeding line models. The embedded optimization algorithm is a trust-region-based gradient search with coarse model Jacobian estimation. We exploit a penalty function approach to ensure that the electrical conditions for the slow-wave lines are accordingly satisfied, apart from explicitly minimizing the area of the coupler. The effectiveness of the proposed technique is demonstrated through a design example of two-section 3-dB branch-line coupler. For the given example, we obtain nine circuit design solutions that correspond to the compact couplers whose multi-element slow-wave lines are composed of unit cells ranging from two to ten.
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Pareto Ranking Bisection Algorithm for EM-Driven Multi-Objective Design of Antennas in Highly-Dimensional Parameter Spaces
(2017) Bekasiewicz, Adrian; Koziel, Slawomir; Leifsson, Leifur; Du, Xiaosong; Department of Engineering
A deterministic technique for fast surrogate-assisted multi-objective design optimization of antennas in highly-dimensional parameters spaces has been discussed. In this two-stage approach, the initial approximation of the Pareto set representing the best compromise between conflicting objectives is obtained using a bisection algorithm which finds new Pareto-optimal designs by dividing the line segments interconnecting previously found optimal points, and executing poll-type search that involves Pareto ranking. The initial Pareto front is generated at the level of the coarsely-discretized EM model of the antenna. In the second stage of the algorithm, the high-fidelity Pareto designs are obtained through optimization of corrected local-approximation models. The considered optimization method is verified using a 17-variable uniplanar antenna operating in ultra-wideband frequency range. The method is compared to three state-of-the-art surrogate-assisted multi-objective optimization algorithms.
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Impact of radiation dose on neurocognitive function and quality of life in long-term survivors of childhood brain tumour
(2025-09-18) Toussaint, Laura; Helligsø, Anne Sophie Lind; Muren, Ludvig Paul; Amidi, Ali; Dahlrot, Rikke Hedegaard; Henriksen, Louise Tram; Maraldo, Maja Vestmø; Nielsen, Martin Skovmos; Trip, Anouk Kirsten; Wu, Lisa Maria; Lassen-Ramshad, Yasmin; Sálfræðideild
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Editorial : People at the heart of projectification: rethinking agency, identity and value creation
(2026-02-20) Wagner, Reinhard Friedrich; Radujković, Mladen; Bond-Barnard, Taryn; Ingason, Helgi Thor; Kalff, Yannick; Department of Engineering
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Generelle tværgående senfølger efter kræft og kræftbehandling
(2026-05-11) Buskbjerg, Cecilie Rask; Amidi, Ali; Wu, Lisa M.; Ventzel, Lise; Lyhne, Johanne Dam; Christiansen, Peer; Christensen, Peter; Jensen, Anders Bonde; Offersen, Birgitte; Johansen, Christoffer; Zachariae, Bobby; Sálfræðideild
Stigningen i antallet af kræfttilfælde kombineret med stadigt mere effektive kræftbehandlinger har resulteret i en markant vækst i antallet af danskere med en nuværende eller tidligere kræftdiagnose. Mere end 400.000 voksne i Danmark lever i dag med eller efter kræft [1]. Flertallet af disse personer oplever en eller flere senfølger som følge af deres kræftsygdom og -behandling – senfølger, som kan have en betydelig negativ indvirkning på livskvaliteten. Anerkendelsen af disse udfordringer afspejles i den nye Kræftplan V, som sætter fokus på»et bedre liv med og efter kræft« [2].

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