Enhanced Planar Antenna Efficiency Through Magnetic Thin-Films

TL;DR

This paper demonstrates that using magnetic thin films as substrates in planar antennas can significantly enhance radiation efficiency, with theoretical derivations and simulations showing up to 25% efficiency improvements.

Contribution

It introduces a theoretical model linking magnetic material properties to antenna efficiency and validates it with simulations, including multilayer laminations to reduce eddy current losses.

Findings

Radiation efficiency improved to 25% with FeGaB thin film.

Multilayer laminations reduce eddy current losses.

Efficiency increased from 2.2% to 11.8% with multilayer ferromagnetic substrates.

Abstract

This work proposes to use magnetic material as the substrate of planar antennas to overcome the platform effect caused by the conducting ground plane. The upper bound of the radiation efficiency of an electric-current-driven low-profile antenna is theoretically derived, which is inversely proportional to the Gilbert damping factor of the magnetic material. Meanwhile, the improvement of radiation due to the use of magnetic material is demonstrated by a three-dimensional (3D) multiphysics and multiscale time-domain model. The simulation results match the theoretical derivation, showing 25% radiation efficiency from a planar antenna backed by a FeGaB thin film with 2.56 um thickness. Furthermore, for conductive ferromagnetic materials, it is shown that the eddy current loss can be well suppressed by laminating the thin film into multiple layers. The radiation efficiency of the modeled antenna with a conductive ferromagnetic substrate is improved from 2.2% to 11.8% by dividing the substrate into 10 layers, with a ferromagnetic material fill factor of 93%.