Programmable
meta-imagers
based
on
reconfigurable
intelligent
surfaces
or
dynamic
metasurface
antennas
constitute
a
promising
low-cost
hardware
layer
for
agile
sensing
in
applications
including
security
screening.
However,
their
calibration
via
near-field
scans
is
tedious,
time
consuming
and
not
easily
compatible
with
large-scale
operations.
In
this
talk,
we
review
recent
efforts
physical-model
wave
control
metasurface-tunable
complex
media
discuss
its
to
the
frugal
of
meta-imagers.
Frugal
here
refers
number
measurements,
parameters
be
stored
later
use,
requirement
phase-sensitive
measurements.
IEEE Transactions on Wireless Communications,
Год журнала:
2024,
Номер
23(8), С. 10001 - 10014
Опубликована: Фев. 28, 2024
We
analytically
derive
from
first
physical
principles
the
functional
dependence
of
wireless
channels
on
RIS
configuration
for
generic
(i.e.,
potentially
complex-scattering)
RIS-parametrized
radio
environments.
The
channel
is
a
linear
input-output
relation
that
depends
non-linearly
because
two
independent
mechanisms:
i)
proximity-induced
mutual
coupling
between
close-by
elements;
ii)
reverberation-induced
long-range
all
elements.
Mathematically,
this
"structural"
non-linearity
originates
inversion
an
"interaction"
matrix
can
be
cast
as
sum
infinite
Born
series
[for
i)]
or
Born-like
ii)]
whose
$K$th
term
physically
represents
paths
involving
$K$
bounces
elements
entities
ii)].
identify
key
parameters
determine
whether
these
truncated
after
and
second
term,
respectively,
tacitly
done
in
common
cascaded
models
channels.
Numerical
results
obtained
with
physics-compliant
PhysFad
model
experimental
prototype
anechoic
(echo-free)
chamber
rich-scattering
reverberation
chambers
corroborate
our
analysis.
Our
findings
raise
doubts
about
reliability
existing
performance
analysis
channel-estimation
protocols
cases
which
poorly
describe
reality.
Laser & Photonics Review,
Год журнала:
2024,
Номер
unknown
Опубликована: Сен. 19, 2024
Abstract
The
scattering
of
waves
in
a
complex
medium
is
perturbed
by
polarizability
changes
or
displacements
embedded
targets.
These
perturbations
can
serve
as
perfectly
non‐invasive
guidestars
for
focusing
on
the
Here,
fundamental
but
to‐date
overlooked
difference
between
these
two
perturbation
types
theoretically
derived:
change
matrix
rank
one
[two]
[displacement]
point‐like
target;
optimal
strategies
to
focus
target
both
cases
are
identified
accordingly.
In
particular,
latter
case,
requires
at
least
displacements.
Furthermore,
case
dynamic
media
additionally
featuring
parasitic
perturbers,
scheme
achieve
time‐averaged
power
delivery
perturbation‐inducing
established.
all
cases,
no
assumptions
about
unitarity
system's
strength
necessary.
All
results
experimentally
demonstrated
microwave
regime
using
strongly
sub‐unitary
lossy
chaotic
cavity
medium.
experiments
highlight
that
target's
“structural
scattering”
irrelevant
[must
be
negligible]
[displacements].
presented
expected
find
applications
communications,
cybersecurity,
wireless
bioelectronics,
flow‐cytometry,
and
self‐propelled
nano‐swimmers.
Advanced Science,
Год журнала:
2025,
Номер
unknown
Опубликована: Фев. 25, 2025
Abstract
Filter
synthesis
is
an
inverse
problem
that
traditionally
approached
rationally
by
engineering
the
coupling
between
selected
pairs
of
lumped
resonators.
The
implicit
restriction
to
spatially
disjoint
resonators
strongly
limits
design
space,
making
it
challenging
build
extremely
tunable
filters.
Here,
agile
free‐form
signal
filtering
and
routing
are
demonstrated
with
alternative
purely‐optimization‐based
approach
leveraging
a
multi‐parameter
programmable
system
many
overlapping
modes.
largely
insensitive
details
other
than
configuration.
In
fabricated
prototype,
all
ports
meta‐elements
coupled
via
quasi‐2D
chaotic
cavity
such
meta‐elements’
configuration
efficiently
controls
transfer
function
ports.
all‐metallic
device
enables
low‐loss
ultra‐wideband
(UWB)
tunability
(7.5–13.5
GHz)
guarantees
signal‐strength‐independent
linearity.
First,
theoretical
predictions
about
reflectionless
transmissionless
scattering
modes
(including
exceptional
points)
experimentally
confirmed.
Second,
these
zeros
imposed
at
desired
frequencies
within
UWB
range.
Third,
achieved.
Fourth,
trade‐off
fidelity
bandwidth
investigated,
achieving
20
dB
discrimination
over
10
MHz
bandwidth.
Fifth,
UWB‐tunable
multi‐band
rejects
(<
–24
dB)
or
passes
(≥
–1
signals
in
specified
bands
whose
centers,
widths
number
reprogrammable.
2022 16th European Conference on Antennas and Propagation (EuCAP),
Год журнала:
2024,
Номер
unknown, С. 1 - 5
Опубликована: Март 17, 2024
Rich
scattering
yields
long
channel
impulse
responses
(CIRs)
with
many
taps
that
thwart
communications
in
resource-constrained
wireless
networks
limited
to
simple
on-off-keying:
the
modulation
rate
must
be
throttled
avoid
inter-symbol
interference.
Relevant
examples
include
Internet-of-Things
(IoT)
and
networks-on-chips
(WNoCs).
If
radio
environment
is
parametrized
by
a
reconfigurable
intelligent
surface
(RIS),
RIS
configuration
can
optimized
tailor
CIR
between
selected
antenna
pairs
make
it
(almost)
pulse-like
despite
rich
judiciously
engineering
interferences
of
multi-bounce
paths.
Thereby,
equalized
"over
air"
physical
domain,
unlike
conventional
pre-
and/or
post-coding
strategies.
Here,
using
physics-compliant
model
RIS-parametrized
rich-scattering
environment,
we
explore
how
optimal
choice
time
delay
at
which
shaped
have
its
most
significant
tap
depends
on
amount
reverberation
latter's
specific
geometry.
2022 16th European Conference on Antennas and Propagation (EuCAP),
Год журнала:
2024,
Номер
unknown, С. 1 - 4
Опубликована: Март 17, 2024
Physics-compliant
models
of
RIS-parametrized
wireless
channels
currently
describe
the
reconfigurability
RIS
elements
either
in
terms
tunable
load
impedances
or
polarizabilities.
No
efforts
to
compare
harmonize
these
two
approaches
exist
date,
and
similar
results
are
independently
derived
with
both
approaches.
Here,
we
approaches,
notably
their
mathematical
complexity.
We
argue
that
polarizability
approach
is
more
"transparent"
because
a
local
concept
configuration
determines
radio
environment's
scattering
properties
at
location
elements.
In
contrast,
impedance
non-local
concept,
matrix
only
serves
as
transit
quantity
deriving
end-to-end
channel
matrix.
conclude
formulation
facilitates
physical
intuition
may
offer
lower
computational
The
latter
matters
for
physics-compliant
estimation,
well
latency
convergence
optimization
algorithms.
Advanced Photonics Congress,
Год журнала:
2024,
Номер
59, С. NoW2D.1 - NoW2D.1
Опубликована: Янв. 1, 2024
Chaotic-cavity-backed
programmable
metasurfaces
experience
significant
coupling
between
meta-atoms
(i.e.,
non-locality)
due
to
reverberation.
We
frugally
calibrate
accurate
physical
models
mapping
metasurface
configurations
scattered
fields
and
discuss
how
they
enable
previously
inaccessible
wave-control
regimes.
