155 research outputs found
Multifunction full space graphene assisted metasurface
In recent years, there has been notable advancement in programmable
metasurfaces, primarily attributed to their cost-effectiveness and capacity to
manipulate electromagnetic (EM) waves. Nevertheless, a significant limitation
of numerous available metasurfaces is their capability to influence wavefronts
only in reflection mode or transmission mode, thus catering to only half of the
spatial coverage. To the best of our knowledge and for the first time, a novel
graphene-assisted reprogrammable metasurface that offers the unprecedented
capability to independently and concurrently manipulate EM waves within both
half-spaces has been introduced in the THz frequency band
Design of Reconfigurable Intelligent Surfaces for Wireless Communication: A Review
Existing literature reviews predominantly focus on the theoretical aspects of
reconfigurable intelligent surfaces (RISs), such as algorithms and models,
while neglecting a thorough examination of the associated hardware components.
To bridge this gap, this research paper presents a comprehensive overview of
the hardware structure of RISs. The paper provides a classification of RIS cell
designs and prototype systems, offering insights into the diverse
configurations and functionalities. Moreover, the study explores potential
future directions for RIS development. Notably, a novel RIS prototype design is
introduced, which integrates seamlessly with a communication system for
performance evaluation through signal gain and image formation experiments. The
results demonstrate the significant potential of RISs in enhancing
communication quality within signal blind zones and facilitating effective
radio wave imaging
On the Enabling of Multi-user Communications with Reconfigurable Intelligent Surfaces
Reconfigurable Intelligent Surface (RIS) composed of programmable actuators
is a promising technology, thanks to its capability in manipulating
Electromagnetic (EM) wavefronts. In particular, RISs have the potential to
provide significant performance improvements for wireless networks. However, to
do so, a proper configuration of the reflection coefficients of the unit cells
in the RIS is required. RISs are sophisticated platforms so the design and
fabrication complexity might be uneconomical for single-user scenarios while a
RIS that can service multi-users justifies the costs. For the first time, we
propose an efficient reconfiguration technique providing the multi-beam
radiation pattern. Thanks to the analytical model the reconfiguration profile
is at hand compared to time-consuming optimization techniques. The outcome can
pave the wave for commercial use of multi-user communication beyond 5G
networks. We analyze the performance of our proposed RIS technology for indoor
and outdoor scenarios, given the broadcast mode of operation. The aforesaid
scenarios encompass some of the most challenging scenarios that wireless
networks encounter. We show that our proposed technique provisions sufficient
gains in the observed channel capacity when the users are close to the RIS in
the indoor office environment scenario. Further, we report more than one order
of magnitude increase in the system throughput given the outdoor environment.
The results prove that RIS with the ability to communicate with multiple users
can empower wireless networks with great capacity
A Beam-Steering Reflectarray Antenna with Arbitrary Linear-Polarization Reconfiguration
This work presents a beam-steering reflectarray antenna capable of achieving
arbitrary linear polarization (LP) reconfiguration. It utilizes a dual-circular
polarization (CP) reconfigurable reflectarray, along with an LP feed horn, to
synthesize a LP beam by combining two reflected CP beams in the same direction.
The LP states can be dynamically adjusted by tuning the phase constants of the
array, which correspondingly modify the wave phases. Experimental validation of
the proposed polarization synthesis concept is conducted using a 1616
dual-CP 1-bit reconfigurable reflectarray operating at 16.8 GHz. This
reflectarray generates reconfigurable LP waves with polarization states of
LP(0), LP(45), LP(90) and LP(135). Furthermore,
it demonstrates the capability to perform beam scanning, allowing for versatile
beam manipulation. The application of this polarization-reconfigurable
beam-steering reflectarray is pertinent to beam alignment and polarization
synchronization in various wireless communication scenarios, including
satellite communication and mobile communication
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