27 research outputs found
Intelligent Metasurfaces with Continuously Tunable Local Surface Impedance for Multiple Reconfigurable Functions
Electromagnetic metasurfaces can be characterized as intelligent if they are
able to perform multiple tunable functions, with the desired response being
controlled by a computer influencing the individual electromagnetic properties
of each metasurface inclusion. In this paper, we present an example of an
intelligent metasurface which operates in the reflection mode in the microwave
frequency range. We numerically show that without changing the main body of the
metasurface we can achieve tunable perfect absorption and tunable anomalous
reflection. The tunability features can be implemented using mixed-signal
integrated circuits (ICs), which can independently vary both the resistance and
reactance, offering complete local control over the complex surface impedance.
The ICs are embedded in the unit cells by connecting two metal patches over a
thin grounded substrate and the reflection property of the intelligent
metasurface can be readily controlled by a computer. Our intelligent
metasurface can have significant influence on future space-time modulated
metasurfaces and a multitude of applications, such as beam steering, energy
harvesting, and communications.Comment: 10 pages, 8 figure
Multi-functional metasurface architecture for amplitude, polarization and wavefront control
Metasurfaces (MSs) have been utilized to manipulate different properties of
electromagnetic waves. By combining local control over the wave amplitude,
phase, and polarization into a single tunable structure, a multi-functional and
reconfigurable metasurface can be realized, capable of full control over
incident radiation. Here, we experimentally validate a multi-functional
metasurface architecture for the microwave regime, where in principle variable
loads are connected behind the backplane to reconfigurably shape the complex
surface impedance. As a proof-of-concept step, we fabricate several metasurface
instances with static loads in different configurations (surface mount
capacitors and resistors of different values in different connection
topologies) to validate the approach and showcase the different achievable
functionalities. Specifically, we show perfect absorption for oblique incidence
(both polarizations), broadband linear polarization conversion, and beam
splitting, demonstrating control over the amplitude, polarization state, and
wavefront, respectively. Measurements are performed in the 4-18 GHz range
inside an anechoic chamber and show good agreement with
theoretically-anticipated results. Our results clearly demonstrate the
practical potential of the proposed architecture for reconfigurable
electromagnetic wave manipulation.Comment: 6 pages, 5 figure
ABSense: Sensing Electromagnetic Waves on Metasurfaces via Ambient Compilation of Full Absorption
Metasurfaces constitute effective media for manipulating and transforming
impinging EM waves. Related studies have explored a series of impactful MS
capabilities and applications in sectors such as wireless communications,
medical imaging and energy harvesting. A key-gap in the existing body of work
is that the attributes of the EM waves to-be-controlled (e.g., direction,
polarity, phase) are known in advance. The present work proposes a practical
solution to the EM wave sensing problem using the intelligent and networked MS
counterparts-the HyperSurfaces (HSFs), without requiring dedicated field
sensors. An nano-network embedded within the HSF iterates over the possible MS
configurations, finding the one that fully absorbs the impinging EM wave, hence
maximizing the energy distribution within the HSF. Using a distributed
consensus approach, the nano-network then matches the found configuration to
the most probable EM wave traits, via a static lookup table that can be created
during the HSF manufacturing. Realistic simulations demonstrate the potential
of the proposed scheme. Moreover, we show that the proposed workflow is the
first-of-its-kind embedded EM compiler, i.e., an autonomic HSF that can
translate high-level EM behavior objectives to the corresponding, low-level EM
actuation commands.Comment: Publication: Proceedings of ACM NANOCOM 2019. This work was funded by
the European Union via the Horizon 2020: Future Emerging Topics call
(FETOPEN), grant EU736876, project VISORSURF (http://www.visorsurf.eu
XR-RF Imaging Enabled by Software-Defined Metasurfaces and Machine Learning: Foundational Vision, Technologies and Challenges
We present a new approach to Extended Reality (XR), denoted as iCOPYWAVES,
which seeks to offer naturally low-latency operation and cost-effectiveness,
overcoming the critical scalability issues faced by existing solutions.
iCOPYWAVES is enabled by emerging PWEs, a recently proposed technology in
wireless communications. Empowered by intelligent (meta)surfaces, PWEs
transform the wave propagation phenomenon into a software-defined process. We
leverage PWEs to i) create, and then ii) selectively copy the scattered RF
wavefront of an object from one location in space to another, where a machine
learning module, accelerated by FPGAs, translates it to visual input for an XR
headset using PWEdriven, RF imaging principles (XR-RF). This makes for an XR
system whose operation is bounded in the physical layer and, hence, has the
prospects for minimal end-to-end latency. Over large distances,
RF-to-fiber/fiber-to-RF is employed to provide intermediate connectivity. The
paper provides a tutorial on the iCOPYWAVES system architecture and workflow. A
proof-of-concept implementation via simulations is provided, demonstrating the
reconstruction of challenging objects in iCOPYWAVES produced computer graphics
Constrained pre-equalization accounting for multi-path fading emulated using large RC networks: applications to wireless and photonics communications
Multi-path propagation is modelled assuming a multi-layer RC network with randomly allocated resistors and capacitors to represent the transmission medium. Due to frequency-selective attenuation, the waveforms associated with each propagation path incur path-dependent distortion. A pre-equalization procedure that takes into account the capabilities of the transmission source as well as the transmission properties of the medium is developed. The problem is cast within a Mixed Integer Linear Programming optimization framework that uses the developed nominal RC network model, with the excitation waveform customized to optimize signal fidelity from the transmitter to the receiver. The objective is to match a Gaussian pulse input accounting for frequency regions where there would be pronounced fading. Simulations are carried out with different network realizations in order to evaluate the sensitivity of the solution with respect to changes in the transmission medium mimicking the multi-path propagation. The proposed approach is of relevance where equalization techniques are difficult to implement. Applications are discussed within the context of emergent communication modalities across the EM spectrum such as light percolation as well as emergent indoor communications assuming various modulation protocols or UWB schemes as well as within the context of space division multiplexing
Design, Fabrication, and Characterization of a Proof-of-Concept Multi-functional Microwave Metasurface using Static Loads
| openaire: EC/H2020/736876/EU//VISORSURFWe present the design, fabrication, and characterization of a proof-of-concept reconfigurable multifunctional metasurface. Our implementation relies on a printed circuit board loaded with commercial-off-the-shelf resistors and capacitors (surface mount devices) to shape the metasurface response in the microwave regime spanning 4-12 GHz. In a broader vision, these static loads are to be replaced by computer-controlled chips, thus realizing a software-defined metamaterial vision. In the current implementation, the same type of board is loaded with different combinations of resistive and reactive loads, to model different configurations and realize the corresponding functionalities, such as absorption, steering, and polarizing. Our anechoic chamber measurements indicate good agreement between simulation and experiment.Peer reviewe