Page 79 - ITU Journal, Future and evolving technologies - Volume 1 (2020), Issue 1, Inaugural issue

ITU Journal on Future and Evolving Technologies, Volume 1 (2020), Issue 1

Departing waves:
Directions, {D'(i)}.
Frequency, {f'(i)}. Global switching Impinging wave:
Bandwidth, {B'(i)}. frequency f sw Direction, D.
Amplitudes, {A'(i)}. Block size << 1/f max Frequency, f max .
Phases,{φ'(i)}. Bandwidth, B.
Polarizations, {J'(i)}. Amplitude, A.
if (f sw >f max ) Phase, φ.
Modulations, {M(i)'}. Polarization, J.
Modulation, M.
IoT Chipset-based
gateway, NICs, and
power supply
connection
Passive Commands
block Tunable >STEER();
and/or
sensory >FOCUS();
>FILTER();
IC >ABSORB();
Tunable block and Sensory >PHASE_ALTER();
IC-to-gateway
interconnection fabric offering Middleware >POLAR_ALTER();
Switch or Bus-type control >MODULATE();
>SENSE();
META-API
Fig. 5 – Overview of the metasurface/metamaterial structure and operating principles.

energy wave. ˆ Wavefront: Steering (reflecting or refracting), split-
Regardless of their geometry and composition, the oper- ting, focusing, collimating, beamforming, scatter-
ating principle of metamaterials remains the same. As ing.
depicted in Fig. 5, an impinging wave of any physical
nature (e.g., EM, mechanical, acoustic, thermal) excites ˆ Bandwidth: Filtering.
the surface elements of a metamaterial, initiating a spa-
tial distribution of energy over and within it. We will ˆ Modulation: Requires embedded actuators that can
call this distribution “exciting-source”. On the other switch states fast enough to yield the targeted mod-
hand, well-known and cross-domain principles state that ulation type [30].
any energy wavefront, which we demand to be emitted
by the metamaterial as a response to the excitation, can ˆ Frequency: Filtering, channel conversion.
be traced back to a corresponding surface energy distri-
bution denoted as “producing-source” [3,6]. Therefore,
ˆ Doppler effect mitigation and non-linear effects [8].
a metamaterial configures its tunable elements to cre-
ate a circuit that morphs the exciting-source into the
Additionally, sensing impinging waves may be consid-
producing-source. In this way, a metamaterial with high
ered one of the above functionalities and, as an outcome,
meta-atom density can perform any kind of energy wave
the embedded sensors can extract information of any of
manipulation that respects the energy preservation prin-
the above parameters related to the incident wave.
ciple. Arguably, the electromagnetism constitutes a very
In this aspect, the role of the contributed metamate-
complex energy type to describe and, as a consequence,
rial API is to model these manipulation types into a
manipulate in this manner, as it is described by two de-
library of software callbacks with appropriate parame-
pendent vectors (electric and magnetic field) as well as
ters. Then, for each callback and assorted parameters,
their relative orientation in space, i.e. polarization (me-
the Metamaterial Middleware produces the correspond-
chanical, acoustic and thermal waves can be described
ing states of the embedded tunable elements that in-
by a single scalar field in space). As such, incoming EM
deed yield the required energy manipulation type. In
waves can be treated in more ways than other energy
other words, a metamaterial coupled with an API and
types. The common types of EM wave manipulation via
a Metamaterial Middleware can be viewed as a hypervi-
metamaterials, reported in the literature [3], can desig-
sor that can host metamaterial functionalities upon user
nate a set of high-level functionality types as follows:
request [8].
ˆ Amplitude: Filtering (band-stop, -pass), absorp- In the following, we focus on EM metamaterials which,
tion. as described, yield the richest API and most complex
Metamaterial Middleware. The expansion to other en-
ˆ Polarization: Waveplates (polarization conversion, ergy domains is discussed via derivation in Section 7.
modulation).
© International Telecommunication Union, 2020 59