Piotr Kurgan

Surrogate-based miniaturization-oriented design of two-section branch-line couplers

A novel methodology for miniaturization-oriented design of a class of wideband branch-line couplers is proposed. The initial design is chosen from a family of optimized circuits that feature a simplified two-section topology. Compact size of the coupler is attained by using quasi-periodic slow-wave structures instead of conventional lines. Our approach explicitly aims at circuit size reduction by adjusting the number of elements within the recurrent slow-wave structure and its designable parameters to reach the smallest coupler layout possible. This is achieved at a low cost by exploiting a surrogate-based optimization (SBO) process with the underlying model of the recurrent slow-wave structure composed of multiple response surface approximations (RSAs). The SBO scheme incorporates adaptively adjusted design specifications to converge in just two iterations. A rapid fine-tuning procedure is applied to account for T-junction effects omitted during the design process. Our methodology is illustrated through a numerical example supported by experimental verification.

Surrogate-assisted multi-objective optimization of compact microwave couplers

Abstract This work presents a rigorous methodology for expedited simulation-driven multi-objective design of microwave couplers with compact footprints. The proposed approach is a viable alternative for computationally expensive population-based metaheuristics and exploits a surrogate-assisted point-by-point Pareto set determination scheme that utilizes – for the sake of computational efficiency – space-mapping-corrected equivalent circuit models. The technique is showcased using a complex design example of a compact rat-race coupler, for which a set of nine alternative design solutions is efficiently identified. The latter design solutions illustrate the best possible trade-offs between conflicting design objectives for the structure at hand, that is, its operational bandwidth and the layout area. The overall design cost corresponds to approximately 20 high-fidelity electromagnetic simulations of the miniaturized coupler. Several selected trade-off designs have been manufactured and measured for the purpose of method validation.

Rapid hierarchical simulation-driven design of compact multi-section branch-line couplers

In this paper, we present a methodology for expedited hierarchical simulation-driven design of miniaturized multi-section branch-line couplers (BLCs). The design process starts from optimization of elementary cells of a slow-wave structure, followed by a fast tuning of their cascade as well as the tuning of the entire coupler. The last two stages exploit surrogate-assisted optimization with the underlying low-fidelity models constructed using local response surface approximations and circuit-theory-based connection of lower-level components (e.g., elementary cells for cascade tuning, etc.). This results in an overall low computational cost of the design optimization process, which is less than three EM simulations of the entire microwave component at hand. The proposed methodology is demonstrated through the design of a novel compact two-section BLC for 0.85 GHz to 1.15 GHz frequency range.

Multi-objective mixed-integer design optimization of planar inductors using surrogate modeling techniques

In this paper, we discuss multi-objective design optimization of planar inductors using surrogate modeling techniques. The goal is to identify the best possible trade-offs between the quality factor of the inductor and its size while maintaining a required value of the inductance at a given operating frequency. The design problem is formulated as a mixed-integer task involving geometry parameters as well as the number of inductor windings. The initial Pareto front is found by optimizing a data-driven surrogate of the structure at hand, further refined by means of response correction techniques. Our considerations are illustrated using a 3.5-nH spiral inductor implemented in 65-nm CMOS technology.

Expedite Design of Variable-Topology Broadband Hybrid Couplers for Size Reduction Using Surrogate-Based Optimization and Co-Simulation Coarse Models

Abstract 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.

Multi-objective EM-driven design of integrated spiral inductors by Pareto front exploration

In this paper, multi-objective design of integrated spiral inductors is investigated. The method aims at finding the best possible trade-offs between inductor size and its quality factor. We adopt a penalty function approach to achieve a required inductance at a given operating frequency. The design process exploits a Pareto front exploration technique with trust-region-embedded gradient search as the optimization engine. Our considerations are illustrated using an example of a 3.5-nH 3.5-turn spiral inductor in a single-ended configuration.

EM-driven design of recurrent slow-wave structures

This work addresses the problem of simultaneous determination of circuit topology and geometry parameter values of recurrent slow-wave structures. Here, the considered slow-wave structures are specifically meant for use as building blocks of two-section branch-line couplers, whose size and bandwidth depend on the aforementioned parameters. The proposed design strategy exploits data-driven models of the coupler components as well as surrogate-assisted techniques to accelerate the geometry optimization process. It allows for obtaining the smallest coupler for a given bandwidth without the necessity of executing multiple optimization routines at the level of the entire EM model of the coupler circuit.

Multi-objective EM-based design optimization of compact branch-line coupler

This work addresses a problem of multi-objective design optimization of a computationally expensive compact branch-line coupler. Circuit miniaturization is achieved here primarily by using intricate slow-wave structures instead of conventional transmission lines. The presented approach exploits a point-by-point Pareto set exploration with consecutive trade-off designs found by applying adjusted design specifications and executing a surrogate-based optimization routine with a low-fidelity model of the slow-wave structure composed of duplicated electromagnetic simulation data blocks of its constitutive element. The optimization engine is a trust-region-embedded gradient search with Jacobian estimation. A set of six Pareto-optimal designs representing trade-offs between the coupler layout area and its bandwidth is obtained at the cost corresponding to less than forty high-fidelity simulations of the entire coupler.

Accelerated multi-objective design of integrated spiral inductors using Pareto front extrapolation

In this work, we demonstrate accelerated multi-objective optimization of integrated inductors by means of Pareto front exploration. The objectives of interest include minimization of the component area, maximization of the quality factor, as well as maintaining required inductance value at a given operating frequency. A set of Pareto-optimal designs is found by moving along the Pareto front using local optimization methods. Considerable reduction of the design cost is achieved by extrapolating inductor dimensions at the subsequent optimal point based on already available data. An illustration example is provided.

Trawl-door shape optimization with 3D CFD models and local surrogates

Design and optimization of trawl-doors are key factors in minimizing the fuel consumption of fishing vessels. This paper discusses optimization of the trawl-door shapes using high-fidelity 3D computational fluid dynamic (CFD) models. The accurate 3D CFD models are computationally expensive and, therefore, the direct use of traditional optimization algorithms, which often require a large number of evaluations, may be prohibitive. The design approach presented here is a variation of sequential approximate optimization exploiting low-order local response surface models of the expensive 3D CFD simulations. The algorithm is applied to the design of modern and airfoil-shaped trawl-doors.