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The specific problems encountered in the design of near-field focused planar microstrip arrays for RFID (Radio Frequency IDentification) readers are described. In particular, the paper analyzes the case of a prototype operating at 2.4 GHz, which has been designed and characterized. Improvements with respect to conventional far-field focused arrays (equal phase arrays) are discussed and quantified

A new phase-based technique for localization and tracking of items moving along a conveyor belt and equipped with UHF-RFID (Ultra High Frequency -Radio Frequency IDentification) tags is here described and validated. 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 I-Q 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 method, also furnishing 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.

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

A detailed performance analysis of near-fi eld-focused planar arrays is addressed. Design curves and performance data are shown for planar square arrays as a function of the array size, the inter-element distance, and the focal distance. The performance curves are compared with results presented in earlier studies relevant to continuous-aperture antennas, as well as with numerical results obtained from a full-wave analysis of planar microstrip array

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

This paper presents a state-of-the-art analysis on the methods suitable for vehicle indoor localization and exploiting the RFID (Radio Frequency IDentification) technology. The survey describes three main categories of vehicle localization systems: (i) solutions exploiting only the RFID technology, (ii) sensor-fusion techniques combining data from RFID systems and proprioceptive sensors, and (iii) sensorfusion techniques combing RFID data with those of other exteroceptive sensors in addition to the RFID system itself. For each method, implementation and methodological details are discussed, by highlighting the applied RFID technology, namely passive HF-RFID, passive UHF-RFID, or any other RFID system. Also, the employed RFID parameters, i.e., tag EPC, RSSI or backscattered phase, are discussed. The survey focuses on the achievable localization performance, also accounting for infrastructure-deployment costs together with complexity and maintenance overhead. Positioning, tracking, navigation and simultaneous localization and mapping (SLAM) issues are here considered. The analysis highlights pros and cons of each method, together with the main challenges and perspectives of RFID-based solutions for vehicle localization.

Abstract-An in-depth survey of wearable antennas for offbody radio links in the VHF and UHF frequency bands (below 1 GHz) is presented. The review encompasses distinctive specifications, design criteria and challenges, material characterization procedures, antenna topologies and technologies, multi-antenna systems, dedicated testing procedures, applications and future trends.Index Terms-Wearable antennas, body-worn antennas, textile antennas, embroidered antennas, VHF antennas, UHF antennas, antennas for body-centric communications, antennas for body area networks, antennas for personal area networks, antennas for off-body wireless communications. I. INTRODUCTIONhere are several existing and forthcoming wireless applications that either require or can benefit from one or more antennas that are directly stitched on a piece of clothing or a garment, or integrated into a personal accessory (such as shoes, glasses, buttons, helmets). These antennas are usually referred to as body-worn antennas, textile antennas, BAN (Body Area Network) antennas, antennas for body-centric communications, wearable antennas. The last term is the one that is going to be used in this paper, as it denotes any antenna that is small and light enough to be worn or carried on one's body.In the last decades, hundreds of scientific papers on wearable antennas have been published in the open literature [1]- [8]. Therefore, for the sake of completeness and clarity, a valuable analysis of the state-of-the-art on wearable antennas should be limited to antennas for a specific application, a given frequency range, or a chosen antenna technology. In this context, the present review focuses on wearable antennas operating in the VHF band and part of the UHF frequency band (below 1 GHz). Choosing 1 GHz as an upper boundary for this review is highly relevant, as the operating frequency is usually the main parameter to discriminate among available antenna topologies, technologies and characterization techniques. Moreover, we limit our discussion on antennas for off-body radio links, also excluding antennas integrated into mobile terminals/cases and operating close to the body. Specifically, only wearable antennas that can be used separately from the radio unit are of interest here.VHF/UHF wearable antennas are mostly used in professional mobile radio communications for soldiers, emergency operators and law-enforcement personnel. VHF As far as VHF/UHF wearable antennas are concerned, many of their distinctive features are related to the fact that the corresponding free-space wavelength (with 30cm<<10m when 30MHz