78 research outputs found
A general, fault tolerant, adaptive, deadlock-free routing protocol for network-on-chip
No full textThe paper presents a topology-agnostic greedy protocol for network-on-chip routing. The proposed routing algorithm can tolerate any number of permanent faults, and is proven to be deadlock-free. We introduce a specialized variant of the algorithm, which is optimized for 2D mesh networks, both flat and wireless. The adaptiveness and minimality of several variants this algorithm are analyzed through graph-based simulations.P. Stroobant is funded by a Ph.D. grant of Ghent University, Special Research Fund (BOF). S. Abadal and E. Alarcon gratefully acknowledge support by the European Commision under grant H2020-FETOPEN-736876 (VISORSURF).Peer ReviewedPostprint (author's final draft
Electromagnetic Aspects of Practical Approaches to Realization of Intelligent Metasurfaces
No full text| openaire: EC/H2020/736876/EU//VISORSURFWe thoroughly investigate the electromagnetic response of intelligent functional metasurfaces. We study two distinct designs operating at different frequency regimes, namely, a switch-fabric-based design for GHz frequencies and a graphene-based approach for THz band, and discuss the respective practical design considerations. The performance for tunable perfect absorption applications is assessed in both cases.Peer reviewe
Tunable Perfect Anomalous Reflection in Metasurfaces with Capacitive Lumped Elements
No full text| openaire: EC/H2020/736876/EU//VISORSURFWe demonstrate tunable perfect anomalous reflection with metasurfaces incorporating lumped elements. The tunable capacitance of each element provides continuous control over the local surface reactance, allowing for controlling the evanescent field distribution and efficiently tilting the reflected wavefront away from the specular direction. The performance of the metasurface is evaluated for both TE and TM polarization and for reflection to the first and second diffraction order.Peer reviewe
Active metasurfaces as a platform for capacitive wireless power transfer supporting multiple receivers
No full text| openaire: EC/H2020/736876/EU//VISORSURFAs wireless power transfer (WPT) repeaters, metasurfaces can enhance field coupling, improving the WPT operation. In this paper, we show that metasurfaces can also be used as transmitters of capacitive WPT systems. Such a metasurface-based WPT system can feed multiple receivers and provide robust operation against load or position variations. We formulate an analytical model of such WPT systems. We also discuss the exact solution of a particular example with N identical receivers.Peer reviewe
Theory and Design of Multifunctional Space-Time Metasurfaces
No full text| openaire: EC/H2020/736876/EU//VISORSURFIntegrating multiple functionalities into a single metasurface is becoming of great interest for future intelligent communication systems. While such devices have been extensively explored for reciprocal functionalities, in this work, we integrate a wide variety of nonreciprocal applications into a single platform. The proposed structure is based on spatiotemporally modulated impedance sheets supported by a grounded dielectric substrate. We show that, by engineering the excitation of evanescent modes, nonreciprocal interactions with impinging waves can be configured at will. We demonstrate a plethora of nonreciprocal components, such as wave isolators, phase shifters, and circulators, on the same metasurface. This platform allows switching between different functionalities by modifying only the pumping signals (harmonic or nonharmonic), without changing the main body of the metasurface structure. This solution opens the door for future real-time reconfigurable and environment-adaptive nonreciprocal wave controllers.Peer reviewe
Toward the Realization of a Programmable Metasurface Absorber Enabled by Custom Integrated Circuit Technology
No full text| openaire: EC/H2020/736876/EU//VISORSURFThe realization of a programmable metasurface, enabled by a custom application-specific integrated circuit (ASIC), is presented in this paper. The ASIC is used to provide an adaptive complex impedance load to each of the metasurface unit cells. Various technology nodes are analyzed for the implementation of tunable complex impedance loading elements before one is selected for the final implementation, in which four complex loads are placed within each integrated circuit, and each load is controlled by two digital-to-analog converters. Furthermore, the ASICs populate the back of the metasurface to form a mesh network to enable programmability. The paper includes practical limitations that affect the realization, as well as an example adaptive metasurface absorber that builds upon the practical tuning range of the ASIC. Perfect absorption for both transverse electric and transverse magnetic polarization is demonstrated.Peer reviewe
Time-Varying Reactive Elements for Extreme Accumulation of Electromagnetic Energy
No full text| openaire: EC/H2020/736876/EU//VISORSURFAccumulation of energy by reactive elements is limited by the amplitude of time-harmonic external sources. In the steady-state regime, all incident power is fully reflected back to the external source, and the stored energy does not increase in time, although the external source continuously supplies energy. Here we show that this limitation can be removed if the reactive element is varying in time, properly modulated by an additional active but lossless device. We show that such time-varying lossless loads of a transmission line or lossless metasurfaces can accumulate electromagnetic energy supplied by a time-harmonic source continuously in time without any theoretical limit. We analytically derive the required time dependence of the load reactance and show that it can, in principle, be realized as a series connection of mixers and filters. Furthermore, we prove that by properly designing time-varying LC circuits, one can arbitrarily engineer the time dependence of the electric current in the circuit fed by a given time-harmonic external source. As an example, we theoretically demonstrate a circuit with a linearly increasing electric current through the inductor. Calculating the energy delivered to the LC circuit and the energy released from it, we show that a modulated LC circuit can accumulate huge energy from both the time-harmonic external source and the modulating device. Finally, we discuss how this stored energy can be released in the form of a time-compressed pulse.Peer reviewe
Graphene-Based Tunable Metasurface for All-Angle Perfect Absorption
No full text| openaire: EC/H2020/736876/EU//VISORSURFMotivated by the idea of »smart» metasurfaces, we will demonstrate a graphene-based tunable absorber in which perfect absorption can be achieved for all angles of incidence, only by tuning the Fermi level of graphene. We place an unpatterned graphene sheet on a mushroom-type high impedance surface whose resonant frequency is stable for all incident angles. For TM-polarization, perfect absorption can be realized from normal to grazing incidence at the same frequency when modulating the Fermi level of graphene from 0.18 eV to 1 eV.Peer reviewe
Toward localization in terahertz-operating energy harvesting software-defined metamaterials: context analysis
No full textSoftware-defined metamaterials (SDMs) represent a novel paradigm for real-time control of metamaterials. SDMs are envisioned to enable a variety of exciting applications in the domains such as smart textiles and sensing in challenging conditions. Many of these applications envisage deformations of the SDM structure (e.g., rolling, bending, stretching). This affects the relative position of the metamaterial elements and requires their localization relative to each other. The question of how to perform such localization is, however, yet to spark in the community. We consider that the metamaterial elements are controlled wirelessly through a Terahertz (THz)-operating nanonetwork. Moreover, we consider the elements to be energy constrained, with their sole powering option being to harvest environmental energy. For such a setup, we demonstrate sub-millimeter accuracy of the two-way Time of Flight (ToF)-based localization, as well as high availability of the service (i.e., consistently more than 80% of the time), which is a result of the low energy consumed in localization. Finally, we provide the localization context for a number of relevant system parameters such as operational frequency, bandwidth, and harvesting rate.The author Filip Lemic was supported by the EU Marie Curie Actions Individual Fellowship project Scalable Localization-enabled Inbody Terahertz Nanonetwork (SCaLeITN), grant nr. 893760. In addition, this work received support from the University of Antwerp’s University Research Fund (BOF). This work also received funding from the European Union via the Horizon 2020 Future Emerging Topics call (FETOPEN), grant no. 736876.Peer ReviewedPostprint (author's final draft
Multifunctional Nonreciprocal Metasurfaces Based on Spatiotemporal Modulation
No full text| openaire: EC/H2020/736876/EU//VISORSURFIn this talk, we put forward the concept of multi-functional nonreciprocal metasurfaces realized on an universal hardware platform. The proposed prototype is based on a spatiotemporally modulated impedance surface. We show that using appropriate traveling wave modulations it is possible to realize various nonreciprocal properties controlling the response for illuminating plane waves. Based on this principle, we find proper modulation functions for different application purposes, which allows us to switch the device functionality among isolators, phase shifters, circulators, and potentially even more functionalities.Peer reviewe
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