Abstract
Design of antennas for the Internet of Things (IoT) applications requires taking into account several performance figures, both electrical (e.g., impedance matching) and field (gain, radiation pattern), but also physical constraints, primarily concerning size limitation. Fulfillment of stringent specifications necessitates the development of topologically complex structures described by a large number of geometry parameters that need tuning. Conventional optimization procedures are typically too expensive when the antenna is evaluated using high-fidelity electromagnetic (EM) analysis, otherwise required to ensure accuracy. This paper proposes a novel surrogate-assisted optimization algorithm for computationally efficient design optimization of antenna structures. In the paper, the optimization of antenna input characteristic is presented, specifically, minimization of the antenna reflection coefficient in a given bandwidth. Our methodology involves variable-fidelity EM simulations as well as a dedicated procedure to reduce the cost of estimating the antenna response gradients. The latter is based on monitoring the variations of the antenna response sensitivities along the optimization path. The procedure suppresses the finite-differentiation-based sensitivity updates for variables that exhibit stable gradient behavior. The proposed algorithm is validated using three compact wideband antennas and demonstrated to outperform both the conventional trust region algorithm and the pattern search procedure, as well as surrogate-based procedures while retaining acceptable design quality.
Highlights
IntroductionOther requirements are dependent on particular applications and may include: (i) multi-band or wideband operation [2,3,4], (ii) excellent matching (e.g., for energy harvesting [5]), (iii) multiple-input multiple-output (MIMO) functionality to ensure transmission channel capacity (e.g., for high data rate wireless access points and mobile users [6,7]), as well as (iv) close-to-isotropic radiation pattern
Design of antennas for the Internet of Things (IoT) poses specific challenges
Other requirements are dependent on particular applications and may include: (i) multi-band or wideband operation [2,3,4], (ii) excellent matching, (iii) multiple-input multiple-output (MIMO) functionality to ensure transmission channel capacity, as well as (iv) close-to-isotropic radiation pattern
Summary
Other requirements are dependent on particular applications and may include: (i) multi-band or wideband operation [2,3,4], (ii) excellent matching (e.g., for energy harvesting [5]), (iii) multiple-input multiple-output (MIMO) functionality to ensure transmission channel capacity (e.g., for high data rate wireless access points and mobile users [6,7]), as well as (iv) close-to-isotropic radiation pattern Another important requirement, common to the majority of IoT applications, is a small size of the device [9,10]. In order to maintain small size and acceptable performance, various topological modifications are being incorporated into the antenna structures which leads to more and more
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