In this article we report our first investigations of a new contactless localizing sensor based on the propagation of slow waves in metamaterials. Using the properties of magnetoinductive waves in a one dimensional metamaterial we are able to unambiguously locate a nearby object. This works because when an object impinges on the near field of the metamaterial's meta-atoms, it introduces a local defect resulting in the reflections of magnetoinductive waves. Key performance metrics are investigated and the ultimate horizontal range of the sensor is demonstrated to be directly linked to the metamaterials quality. An algorithm is devised based on the standing waves modes. The effect of terminating the structure with a matching impedance is discussed. Unambiguous localization of a single object is possible using a low-complexity algorithm, when the object interacts strongly with the metamaterial structure.

A tri-band 2×2 MIMO antenna array for 5G applications is presented. It consists of two orthogonally-placed compact tri-band 28/38/60 GHz antennas with the realized gain varying between 3.5 and 8.5 dBi over the operating frequencies. Each individual antenna maintains a monopole-like radiation pattern across these bands. In addition, the MIMO characterization of the proposed array is discussed. The simulation results show that the envelope correlation coefficient of the array is excellent with a maximum value of less than 0.0015 whereas the diversity gain almost attains 10 dB over the entire operating frequency. The simple planar structure of the MIMO array also offers an ease of fabrication and practical integration with other electronic components Index Terms-Ultra wideband antenna, multi-band antenna, MIMO antenna, 5G antenna.

We demonstrate switchable unidirectional propagation of slow waves of coupling within a metamaterial array of strongly coupled elements. We predict theoretically and verify experimentally that the direction of propagation of magnetoinductive waves for any chosen excitation pattern is dictated by the dispersion relations, with forward and backward waves propagating in opposite directions along a chain of meta-atoms. We further prove that the same fundamental phenomenon of direction selectivity due to the forward/backward wave nature is not limited to magnetoinductive waves: we predict analytically and verify numerically the same selective unidirectional signal propagation occurring in nanostructured metamaterial arrays with purely electric coupling. Generalising our method of unidirectional waveguiding to a diatomic magnetoinductive array featuring both forward-wave and backward-wave dispersion branches, switchable unidirectional signal propagation is achieved with distinct frequency bands with opposite directions of signal propagation. Finally, by expanding our technique of selective unidirectional waveguiding to a 2D metasurface, a selective directional control of waves in two dimensions is demonstrated opening up possibilities for directional wireless signal transfer via magnetoinductive surfaces. The observed phenomenon is analogous to polarisation-controlled near-field interference for unidirectional guiding of surface plasmon-polaritons.

The capability of magnetic induction to transmit signals in attenuating environments has recently gained significant research interest. The wave aspect—magnetoinductive (MI) waves—has been proposed for numerous applications in RF-challenging environments, such as underground/underwater wireless networks, body area networks, and in-vivo medical diagnosis and treatment applications, to name but a few, where conventional electromagnetic waves have a number of limitations, most notably losses. To date, the effects of eddy currents inside the dissipative medium have not been characterised analytically. Here we propose a comprehensive circuit model of coupled resonators in a homogeneous dissipative medium, that takes into account all the electromagnetic effects of eddy currents, and, thereby, derive a general dispersion equation for the MI waves. We also report laboratory experiments to confirm our findings. Our work will serve as a fundamental model for design and analysis of every system employing MI waves or more generally, magnetically-coupled circuits in attenuating media.