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Modeling of spherical metasurfaces using generalized sheet transition conditions (GSTCs) and vector wave function (VWF) expansion is presented. The fields internal and external to the metasurface are expanded in terms of spherical VWFs and unknown coefficients. The GSTCs are used to obtain linear relationships between the unknown coefficients. An overdetermined system of equations is then solved by point matching. The method is quasi-analytical, and hence there is no need for meshing, which is encountered in conventional computational electromagnetic methods. This results in the method being extremely fast and hence useful for metasurface optimization. The method is validated by two examples. The formulations presented here can be easily extended to multilayered spherical metasurfaces.

In magnetic resonance imaging (MRI), several studies have demonstrated that the metamaterial-based structures can effectively improve the sensitivity, and thus the signal-to-noise ratio (SNR), of receiving radio-frequency (RF) coils. However, the use of metamaterials for this type of the MRI application is often limited due to the bulkiness of the metamaterial structure at RF wavelengths and a lack of frequency tunability of the final design. In this work, we propose a planar compact sub-wavelength (1- field at the depth of 30mm into a load experimentally. Even at a penetration depth as much as 60 mm (deep brain in the case of head imaging), an enhancement of 9% was observed. Moreover, the magnetic field enhancement comes with a decrease (10%) in specific absorption rate (SAR). In terms of tuning, by controlling the water level in the cavity, the proposed spiral resonator shows a wide tuning range of 35MHz, centered around 64 MHz, with high tunability sensitivity (2.4-0.75 MHz/ml or 15-4.8 MHz/mm), which is due to the fact that the tuning cavity is located between the two spirals, where the fields are highly confined.

A modeling of metasurfaces in the finite-element method (FEM) based on generalized sheet transition conditions (GSTCs) is presented. The discontinuities in electromagnetic fields across a metasurface as represented by the GSTC are modeled by assigning nodes to both the sides of the metasurface. The FEM-GSTC formulation in both 1-D and 2-D domains is derived and implemented. The method is extended to handle more general bianistroptic metasurfaces. The formulations are validated by several illustrative examples.

Conventional strongly coupled magnetic resonance (SCMR) wireless power transfer (WPT) systems have high quality factor ( $Q$ ), leading to limited system bandwidths. In practical applications, especially in human-involved environments, the resonant frequency of SCMR resonators will shift due to the effect of highly dielectric human body. In this letter, a wideband four-coil SCMR WPT system is proposed by improving the coupling between the tx/rx coil and their corresponding resonators. The bandwidth is increased by over 100% compared to a conventional system without sacrificing the efficiency much. The wideband feature is demonstrated by both simulation and measurement. It is analyzed physically and by using an equivalent circuit analysis.

In this paper an algorithm is described for obtaining the response of Power Distribution Networks (PDN) arising in chip, package or pcb during an early design phase. Results are provided for power grids arising in silicon interposers to validate the approach.

In this paper a forward-looking synthetic aperture radar (IceSAR) system is described for the ‘Very deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice explorer’ (VALKYRIE) project. Fabrication and laboratory characterization of novel log periodic antennas for IceSAR and system design and in situ testing of the synthetic aperture radar system are presented.