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Radio frequency identification (RFID) is a mature technology that allows contactless reading of data via a wireless communication link. While communication protocols in this field are subject to international regulations, there are plenty of opportunities to improve hardware realization of antenna devices that support this technology. In particular, readout range extension and miniaturization of passive RFID tags is an important challenge with far-reaching goals. Here, we introduce and analyze a new concept of high-permittivity ceramic tag that relies on different physical principles. Instead of using conduction currents in metallic wires to drive electronic chips and generate electromagnetic radiation, high-permittivity components rely on excitation of displacement currents. Those are efficiently converted to actual electric current which drives the memory chip. Practical aspects of this approach are improved robustness to environmental fluctuations, footprint reduction, and readout range extension. In particular, our high-permittivity ceramic (ε ~ 100) elements have demonstrated a 25% reading range improvement in comparison to commercial tags. In case when state-of-the-art readers and RFID chips are used, the readout distances of the developed ceramic tags can reach 22 m. This number can be further extended with improved matching circuits. Miniature RFID tags, capable to establish long-range communication channels, can find use in many applications, including retail, security, Internet of Things, and many others. [ABSTRACT FROM AUTHOR]

Dielectric resonators made of high permittivity materials with low losses have been extensively studied for application in magnetic resonance imaging (MRI) and magnetic resonance spectroscopy. They can focus, redistribute, and enhance the radio frequency magnetic field in a controlled way. In this Letter, we investigate coupled very-high permittivity dielectric resonators for clinical bilateral breast MRI. The resonators are tuned to support a TE mode within the frequency of 3 T MRI and implemented as a pair of coaxial hollow cylinders consisting of ceramic rings with extremely high permittivity (ε ∼ 870) and low loss. We study the electromagnetic coupling between two resonators placed in the near field and analyze the impact of symmetric and antisymmetric mode excitation on the sensitivity of the MRI machine. We experimentally verify that the coupling of the mode with symmetric field distribution to the radio frequency body birdcage coil allows us to enhance the receive sensitivity substantially and to decrease the excitation power needed to provide the optimal transmit efficiency, thus making the MRI procedure safer. Our work offers a practical method to realize a simple yet very effective system based on dielectric resonators for bilateral breast imaging. [ABSTRACT FROM AUTHOR]

Metasurfaces is a rapidly developing area with quite many prospective applications in light manipulation, aberration‐free optical imaging, and security. One potential area where metasurface approaches may provide a valuable contribution is medical imaging. In this paper, a novel subwavelength metasurface‐inspired resonator design is presented, which is employed to enhance the sensitivity of magnetic resonance imaging (MRI). To this end, the resonator is formed by an array of capacitively loaded telescopic wires is placed inside the scanner in a close proximity of the studied object. The telescopic design of the structure permits to mechanically adjust its eigenmode resonance frequency to the operational frequency of a 1.5T MRI machine, thus making it possible to enhance and redistribute the radiofrequency magnetic field of an available radiofrequency coil in the region of interest and therefore significantly increase the sensitivity of the receiver. [ABSTRACT FROM AUTHOR]

The sensitivity of magnetic resonance imaging (MRI) is dictated by the signal-to-noise ratio. It was recently noted that the signal-to-noise ratio could be substantially increased via excitation of certain metasurface eigenmodes. Here, we provide a detailed discussion of the wire metasurface eigenmode impact on the sensitivity of MRI. We experimentally show that due to the spatial redistribution of the electromagnetic near field, mediated by the metasurface eigenmode, the received signal from the studied object becomes essentially dependent on its position on the metasurface. Moreover, we analyzed how the metasurface performance significantly depends on the dimensions of an examined object. Our work provides metasurface design guidelines for substantial enhancement of MRI sensitivity. [ABSTRACT FROM AUTHOR]

In this work, we experimentally demonstrate an increase in the local transmit efficiency of a 1.5 T MRI scanner by using a metasurface formed by an array of brass wires embedded in a high permittivity low loss medium. Placement of such a structure inside the scanner results in strong coupling of the radiofrequency field produced by the body coil with the lowest frequency electromagnetic eigenmode of the metasurface. This leads to spatial redistribution of the near fields with enhancement of the local magnetic field and an increase in the transmit efficiency per square root maximum specific absorption rate in the region-of-interest. We have investigated this structure in vivo and achieved a factor of 3.3 enhancement in the local radiofrequency transmit efficiency. [ABSTRACT FROM AUTHOR]

The concepts of many optical devices are based on fundamental physical phenomena such as resonances. One of the commonly used devices is an electromagnetic antenna that converts localized energy into freely propagating radiation and vise versa, offering unique capabilities for controlling electromagnetic radiation. Here we propose a concept for controlling the intensity and directionality of electromagnetic wave scattering in radio-frequency and optical antennas based on the physics of Fano resonances. We develop an analytical theory of spatial Fano resonances in antennas that describes switching of the radiation pattern between the forward and backward directions, and we confirm our theory with both numerical calculations and microwave experiments. Our approach bridges the concepts of conventional radio antennas and photonic nanoantennas, and it provides a paradigm for the design of wireless optical devices with various functionalities and architectures. [ABSTRACT FROM AUTHOR]