[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Reconfigurable intelligent surfaces (RISs) comprised of tunable unit cells have recently drawn significant attention due to their superior capability in manipulating electromagnetic waves. In particular, RIS-assisted wireless communications have the great potential to achieve significant performance improvement and coverage enhancement in a cost-effective and energy-efficient manner, by properly programming the reflection coefficients of the unit cells of RISs. In this paper, free-space path loss models for RIS-assisted wireless communications are developed for different scenarios by studying the physics and electromagnetic nature of RISs. The proposed models, which are first validated through extensive simulation results, reveal the relationships between the free-space path loss of RIS-assisted wireless communications and the distances from the transmitter/receiver to the RIS, the size of the RIS, the near-field/far-field effects of the RIS, and the radiation patterns of antennas and unit cells. In addition, three fabricated RISs (metasurfaces) are utilized to further corroborate the theoretical findings through experimental measurements conducted in a microwave anechoic chamber. The measurement results match well with the modeling results, thus validating the proposed free-space path loss models for RIS, which may pave the way for further theoretical studies and practical applications in this field.

/pdf/wireless-communications-with-reconfigurable-intelligent-2kgnsznjwk.pdf

Wireless Communications with Reconfigurable Intelligent Surface: Path Loss Modeling and Experimental Measurement

Reconfigurable intelligent surfaces (RISs) comprised of tunable unit cells have recently drawn significant attention due to their superior capability in manipulating electromagnetic waves. In particular, RIS-assisted wireless communications have the great potential to achieve significant performance improvement and coverage enhancement in a cost-effective and energy-efficient manner, by properly programming the reflection coefficients of the unit cells of RISs. In this article, free-space path loss models for RIS-assisted wireless communications are developed for different scenarios by studying the physics and electromagnetic nature of RISs. The proposed models, which are first validated through extensive simulation results, reveal the relationships between the free-space path loss of RIS-assisted wireless communications and the distances from the transmitter/receiver to the RIS, the size of the RIS, the near-field/far-field effects of the RIS, and the radiation patterns of antennas and unit cells. In addition, three fabricated RISs (metasurfaces) are utilized to further corroborate the theoretical findings through experimental measurements conducted in a microwave anechoic chamber. The measurement results match well with the modeling results, thus validating the proposed free-space path loss models for RISs, which may pave the way for further theoretical studies and practical applications in this field.

/pdf/wireless-communications-with-reconfigurable-intelligent-1lxbm2f77o.pdf

Wireless Communications With Reconfigurable Intelligent Surface: Path Loss Modeling and Experimental Measurement

A new phase-based technique for localization and tracking of items moving along a conveyor belt and equipped with ultrahigh frequency-radio frequency identification (UHF-RFID) tags is described and validated here. The technique is based on a synthetic-array approach that takes advantage of the fact that the tagged items move along a conveyor belt whose speed and path are known a priori. In this framework, a joint use is done of synthetic-array radar principles, knowledge-based processing, and efficient exploitation of the reader-tag communication signal. The technique can be easily implemented in any conventional reader based on an in-phase and quadrature receiver and it does not require any modification of the reader antenna configurations usually adopted in UHF-RFID portals. Numerical results are used to investigate the performance analysis of such methods, and also to furnish system design guidelines. Finally, the localization capability is also demonstrated through a measurement campaign in a real conveyor belt scenario, showing that a centimeter-order accuracy in the tag position estimation can be achieved even in a rich multipath environment.

/pdf/a-phase-based-technique-for-localization-of-uhf-rfid-tags-50xhxx56ga.pdf

A Phase-Based Technique for Localization of UHF-RFID Tags Moving on a Conveyor Belt: Performance Analysis and Test-Case Measurements

Focusing the electromagnetic field radiated by an antenna at a point in the antenna near-field (NF) region is a wellknown technique to increase the electromagnetic power density in a size-limited spot region close to the antenna aperture. This article encompasses the basic working principles and the applications of the NF-focused (NFF) microwave antennas as well as the synthesis procedures suggested for the NF shaping around the focal point and the technologies currently used for their implementation.

/pdf/near-field-focused-microwave-antennas-near-field-shaping-and-46fyrtzm1f.pdf

Near-Field-Focused Microwave Antennas: Near-field shaping and implementation.

The design of a reflectarray antenna is presented when the radiated field is focused in the near-zone of the array aperture. In particular, the reflectarray antenna is implemented for RFID reader applications at 2.4 GHz. Numerical investigations on the radiation characteristics of this reflectarray, as well as an experimental validation, are presented to demonstrate its feasibility.

Design of a Near-Field Focused Reflectarray Antenna for 2.4 GHz RFID Reader Applications

We present an efficient procedure for the synthesis of planar array antennas to radiate contoured patterns in the near zone of array aperture, as desired in RFID applications. It first grids the target area, and then utilizes a global basis set to span the array's excitations. Each basis's excitation of the array radiates a focused spot beam in the near zone and serves as a local basis function for representing the radiation field. The unknown coefficients of the array's basis set are then found via a minimum least square error (MLSE) technique. It is found that only a small number of basis functions are sufficient to synthesize the radiation pattern, and make the present approach very fast.

An Effective Synthesis of Planar Array Antennas for Producing Near-Field Contoured Patterns

This communication examines how to improve the squinted radiation patterns produced by the balanced antipodal Vivaldi antenna (BAVA) while retaining its cross-polarization levels. In particular, we propose discarding the redundant substrate between the metal flares of the BAVA and implementing dual-scale slotted edges to improve the radiation characteristics. The gain at both the lower and the higher end of the band is significantly enhanced without increasing the antenna size. Moreover, significant reduction in the beam squint relative to the conventional BAVA designs is achieved. A microstrip-to-stripline transition is also introduced to improve low-end matching. The final design operates over 10–40 GHz with return loss <−10 dB, providing sufficient bandwidth and match for a variety of applications at millimeter-wave frequencies. Numerical and experimental assessments to validate the proposed antenna design are conducted.

Balanced Antipodal Vivaldi Antenna With Asymmetric Substrate Cutout and Dual-Scale Slotted Edges for Ultrawideband Operation at Millimeter-Wave Frequencies

Rectangular dielectric resonator antenna with polarization reconfigurable characteristic

This paper presents characteristic comparisons between array, reflectarray and elliptic reflector antennas which can be implemented to radiate fields focused in the near zone of antenna aperture. A potential application, as to be demonstrated later in this paper, is for RFID reader applications at 2.4 GHz. The comparisons include beamwidth, field strength and contoured patterns, which allows one to justify the selection of a proper antenna type for practical applications.

Nannan Wang

Papers

Design of a Near-Field Focused Reflectarray Antenna for 2.4 GHz RFID Reader Applications

An Effective Synthesis of Planar Array Antennas for Producing Near-Field Contoured Patterns

Balanced Antipodal Vivaldi Antenna With Asymmetric Substrate Cutout and Dual-Scale Slotted Edges for Ultrawideband Operation at Millimeter-Wave Frequencies

Rectangular dielectric resonator antenna with polarization reconfigurable characteristic

Characteristic comparisons between array, reflectarray and elliptic reflector antennas in RFID near-field focused communications