An ultra-thin double-functional metasurface patch antenna for UHF RFID applications

Abstract

An ultra-thin double-functional metasurface patch antenna (MPA) was proposed, where it can operate not only in the antenna mode but also can simultaneously act as perfect absorber for normal incident waves, suitable for RFID applications in the 868 MHz band. The MPA structure consists of a typical coaxially-fed patch antenna merged, for the first time, with a metasurface absorber acting as artificial ground. A methodology for the unit-cell design of the metasurface is proposed followed by an equivalent circuit model analysis, which makes it possible to transform a low-loss ($$tan\delta =0.0015$$ t a n δ = 0.0015 ) unit-cell with highly-reflective characteristics to a perfect absorber for normal incident waves. It is based on modifying the critical external coupling by properly introducing slits on the unit-cell, allowing to design an ultra-thin ($$\lambda _0/225$$ λ 0 / 225 at 868 MHz) and a very compact structure in comparison to previously developed designs. For validation purposes, the MPA was fabricated and its performances in both functional modes were characterized numerically and experimentally. It is demonstrated that merging the absorber with the patch not only allows obtaining a well-matched ($$|S_{11}|<-30$$ | S 11 | < - 30 dB) antenna with an enhanced gain (by 175.6% compared to a typical patch) at the desired frequency but also leads to an overall thickness of only 2.5 mm ($$\lambda _0/138.1$$ λ 0 / 138.1 at 868 MHz). With an absorber size limited to the MPA dimensions, a reasonable 1.3 dB reduction in powers reflected by the MPA was achieved compared to a similar size metallic sheet. Whilst having the lowest profile among the so far reported RFID readers, the proposed MPA can be conveniently fitted for example within the required volume of smart shelf RFID readers or used in portable RFID readers while being capable of mitigating multipath reflection issues and incorrect reading of RFID.

Platform Tolerant RFID Tag Antenna Design for Safety and Real-Time Tracking of On-site Workers at Riskier Workplaces

“…Hence, RFID is not only being employed for identifcation but also for special applications, e.g., hydrogen concentration monitoring [8], structural health monitoring [9], screw relaxing monitoring [10], and human parameters monitoring [11]. Tis is possible due to its benefts of easy deployment and low-cost solutions [12][13][14]. IoT-enabled RFID systems are also pivotal for achieving accurate tracking and efective access control at construction sites.…”

Dual‐polarized metasurface‐based monopole antenna design using characteristics mode theory for UHF RFID applications

“…The other technical aspects for UHF RFID applicants include low profile, high gain, and maximized polarization diversity (CP), which can be served as great resource for surrounding wireless connectivity. The metasurface (MTS) 3–47 has distinctive reflection traits responsible for improving performances, enhancement in impedance bandwidth, polarization, and gain, when incorporated in UHF RFID 48 . Due to high‐demand of UHF RFID applications toward automation, tracking, identification, security, logistics management, and so on, the antenna performance metrics like −10 dB impedance bandwidth (IBW), 3‐dB axial ratio bandwidth (ARBW), and CP gain need to be enhanced for scalability.…”

“…The metasurface (MTS) has distinctive reflection traits responsible for improving performances, enhancement in impedance bandwidth, polarization, and gain, when incorporated in UHF RFID. 48 Due to highdemand of UHF RFID applications toward automation, tracking, identification, security, logistics management, and so on, the antenna performance metrics like À10 dB impedance bandwidth (IBW), 3-dB axial ratio bandwidth (ARBW), and CP gain need to be enhanced for scalability. To understand insights about importance of CP, aimed to minimize polarization mismatch in between readers and tags; evaluation of characteristics mode analysis (CMA) [49][50][51][52][53][54][55] is performed, that help in predicting modal significance (MS), modal current, modal pattern, characteristics angle (φ n ), and eigen value (EV) for different antenna models.…”

A drawer‐conformal radio‐frequency identification antenna with vertically polarised quasi‐endfire radiation

“…Ref. [3] proposed a metasurfarce-based RFID antenna with an ultra-low profile. The adopted metasurfarce can be used for antenna operation and scattering reduction simultaneously.…”