Recently, the use of deflecting covering meta-domes for increasing the scanning range of a phased array has been proposed. Although promising, this solution still presents some inherent limitations such as the significant reduction of the broadside gain compared to the original array, as well as the complexity of the implementation due to the need for a continuous phase profile. This work aims at proposing some technical solutions for maximizing the meta-dome performance and reducing the gain-loss at broadside. By properly discretizing and engineering the phase profile along the dome and by taking into account the different angles of incidence onto the meta-cells, we show how it is possible designing realistic meta-domes with reduced insertion loss at broadside, improved steering capabilities, and a reduced profile.

The beamforming capabilities of conformal cylindrical Huygens metasurface (HMS) coatings for linear antennas are assessed. It is shown that by engineering the phase-gradient profile of the HMS, the original omnidirectional radiation pattern of the linear antenna can be shaped to form multi- or single-beam configurations. A closed-form expression for the phase-insertion profile of the cylindrical coating required to achieve the desired radiation pattern profile is derived, and several full-wave numerical examples supporting our claims are reported. A configuration exploiting a realistic HMS layout is also discussed and it is shown that, by making the metasurface reconfigurable through the use of tunable lumped elements, the radiated beams can be dynamically steered in space. This new design methodology could find application in smart electromagnetic environment scenarios for dynamically rerouting the signal towards multiple users.

The development of the next generation of wireless systems is bringing renewed attention to the physical layer of the communication link. Indeed, the new low-latency requirements cannot be satisfied relying only upon the extreme virtualization of the hardware functions. Moreover, conventional wireless systems with fixed characteristics and functionalities are not appropriate to modern electromagnetic environments, which undergo continuous and fast variations. Embedded smartness is a required feature for widening the range of the possible electromagnetic responses to support advanced and novel functionalities. In this paper, we show how the combination of 2D metastructures with conventional antennas and reflectors enables an unprecedented electromagnetic behavior, which is at the basis of new properties, capabilities, and applications. In particular, we propose an emerging design approach based on the shifting of the reconfigurability, adaptivity, sensing, and power management of a wireless system at the physical level, thanks to the use of properly designed 2D metastructures to be coupled with standard antennas and reflectors.

In this contribution, we discuss the modeling of cylindrical Huygens metasurfaces wrapping linear antennas through the array antenna theory. In particular, it is shown that the circular array pattern synthesis can be efficiently exploited to model conformal metasurfaces used for wavefront manipulation in view of beamforming applications. By considering the metasurface unit-cells as the equivalent radiating sources of a circular array, the shape of the emerging radiation pattern is accurately predicted. The proposed approach is validated through several examples where the radiation patterns are modified acting on the excitation phases of the equivalent circular array sources, and are compared with full-wave numerical simulations considering ideal coating metasurfaces designed with conventional techniques. This innovative design strategy allows to further expands the possibility enabled by metasurface coatings in radiation pattern manipulation, potentially improving the functionality of metasurfaces through full control over the radiation characteristics.

Tag-copter is an architecture of dynamic and self-relocating sensor devices originating from the synergy between sensor-oriented radiofrequency identification (RFID) and the emerging micro air vehicles technology. Tag-copters integrate a low-cost nano multi-copter with a miniaturized RFID data-logger antenna for the ubiquitous and cooperative monitoring of indoor volumes as well as of harsh environments. This concept is preliminary exploited by means of a theoretical formulation to derive the upper-bound performance of a flying “winged sensor.” The analysis addresses the sensing accuracy versus the flight speed and the reliability of the on-the-flight data exchange with a fixed base-station through backscattering modulation. A first working 16 g prototype, capable of temperature measurement and storage, is experimented in a controlled setup to corroborate theoretical and experimental findings. The same device is then applied in realistic conditions concerning the temperature mapping within indoor environments. Preliminary results demonstrate that the maximum temperature measurement error is of the order of 1 °C along flight trajectories of 30 m. Finally, most of the data stored within the datalogger memory can be correctly uploaded by a flying tag-copter toward a fixed reader provided that the copter flies at approximatively 1 - 1.5 m from it.

The design of metasurface-based devices (e.g. reflective intelligent surfaces - RIS) is inherently affected by unpredictable variations of the unit-cell response, due to undesired coupling effects among adjacent unit-cells, fabrication tolerances, physical discontinuities, the presence of bumps, etc. Such variations may dramatically affect the accuracy of the conventional design models. In this work, we present a statistical model resulting in a probability density function that allows defining a random local surface impedance (rLSI), that considers potential random variations derived from the von Mises distribution. To compensate for these variations, we propose a transformation kernel that matches the expected value to the design target value. By using an analytical formulation and a proper set of full-wave simulations, we demonstrate the effectiveness and robustness of the method against unpredictable variations caused by the mutual coupling among the unit-cells and fabrication tolerances/errors. The proposed method paves the way to foster advancements in realistic metasurface engineering.