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NFC and RFID technologies have seen significant advancements, with expanding applications necessitating the design of novel antenna structures that enhance range capabilities. This paper presents a study on the design and impedance matching of long-range NFC coils, focusing on optimizing antenna performance over distances exceeding one meter. Through numerical analyses of various coil geometries, including single-turn and multi-wire configurations, we explore the effects of coil size, wire separation, and current distribution on magnetic field generation. Additionally, an adaptive impedance matching approach is proposed to maintain efficient power transfer, significantly improving field strength and system performance. The proposed designs demonstrate superior interrogation distances compared to existing configurations, highlighting the potential for enhanced long-range NFC applications., Comment: 5 pages, 3 figures

Hyperbolic metamaterials were initially proposed in optics to boost radiation efficiencies of quantum emitters. Adopting this concept for antenna design can allow approaching long-standing challenges in radio physics. For example, impedance matching and gain are among the most challenging antenna parameters to achieve in case when a broadband operation is needed. Here we pro-pose and numerically analyse a new compact antenna design, based on hyperbolic metamaterial slab with a patterned layer on top. Energy from a subwavelength loop antenna is shown to be efficiently harvested into bulk modes of the metamaterial over a broad frequency range. Highly localized propagating waves within the medium have a well-resolved spatial-temporal separation owing to the hyperbolic type of effective permeability tensor. This strong interplay between chromatic and modal dispersions enables routing different frequencies into different spatial locations within compact subwavelength geometry. An array of non-overlapping resonant elements is placed on the metamaterial layer and provides a superior matching of localized electromagnetic energy to the free space radiation. As the result, two-order of magnitude improvement in linear gain of the device is predicted. The proposed new architecture can find a use in applications, where multiband or broadband compact devices are required.

Radio frequency identification (RFID) is a mature technology, which allows performing contactless data readout via wireless communication links. While communication protocols in this field are subject to regulations, there is a room of opportunities to improve the hardware realization of antennas devices, which support the technology. In particular, readout range extension and miniaturization of passive RFID tags is an important objective with far going impact on retail, security, IoT, and many others. Here we introduce a new concept of high-permittivity ceramic tag, which relies on different physical principles. Instead of using conduction currents in metallic wires to drive electronic chips and radiate electromagnetic waves, high permittivity components rely on an efficient excitation of displacement currents. Those are efficiently converted to conduction currents, powering a memory chip. The practical aspect of this approach is improved robustness to environmental fluctuations, footprint reduction, and readout range extension. In particular, our high permittivity ceramic ({\epsilon} ~ 100) elements have demonstrated a 25% reading range improvement in respect to commercial tags. In case, when state of the art readers and RFID chips are used, the readout distances of the developed ceramic tags are approaching 23 m and could be further extended with improved matching circuits.