Experimental Demonstration of a Structured Material with Extreme Effective Parameters at Microwaves

Following our recent theoretical studies [M. G. Silveirinha, C. A. Fernandes, Phys. Rev. B, 78, 033108, 2008], it is experimentally verified that an array of crossed metallic wires may behave as a nonresonant material with extremely large index of refraction at microwaves, and may enable the realization of ultra-subwavelength waveguides.Comment: accepted for publication in Applied Physics Letters (in press). Applied Physics Letters (in press) (2008

Revealing hidden symmetries and gauge invariance of the massive Carroll-Field-Jackiw model

In this paper we have analyzed the improved version of the Gauge Unfixing (GU) formalism of the massive Carroll-Field-Jackiw model, which breaks both the Lorentz and gauge invariances, to disclose hidden symmetries to obtain gauge invariance, the key stone of the Standard Model. In this process, as usual, we have converted this second-class system into a first-class one and we have obtained two gauge invariant models. We have verified that the Poisson brackets involving the gauge invariant variables, obtained through the GU formalism, coincide with the Dirac brackets between the original second-class variables of the phase space. Finally, we have obtained two gauge invariant Lagrangians where one of them represents the Stueckelberg form.Comment: revised version. To appear in Europhysics Letter

RFID reader antennas for TAG detection in self-confined volumes at UHF

WOS:000300358000004 (Nº de Acesso Web of Science)“Prémio Científico ISCTE-IUL 2012”Confinement of the detection region is a critical issue for some important RFID applications, where the coarse location of the object is required along with its identification. In the UHF band, it is a challenge to confine antenna radiation to reasonably sharp interrogation volumes, <; 10λ3, without resorting to physical barriers. This paper presents a novel approach for RFID reader radiating structures that self-confine tag detection to a desired volume, avoiding undesired readings outside the interrogation volume. The proposed solution simultaneously covers the three world-assigned RFID frequency subbands at UHF. To demonstrate the effectiveness of the solution, the proposed configuration was integrated into bookshelves, a conveyor belt system, and a proximity point reader. Together with an appropriate control application, these form the building blocks of a smart store with automatic inventorying and billing capability. The radiating structure concept was explored by full-wave simulations, and it was validated with both near-field measurements and with tag-reading scores. Short demonstration videos are available online

Compact tapered slot UWB antenna with WLAN band rejection

WOS:000268020000048 (Nº de Acesso Web of Science)This letter extends the design of a previously proposed uniplanar ultrawideband (UWB) antenna to include within its 3.110.6-GHz operation band a rejection of the wireless local area network (WLAN) band near 5.5 GHz. The antenna configuration is based on a combination of two crossed exponentially tapered slots plus a star-shaped slot printed on both sides of a 10-mils dielectric substrate. The band rejection is obtained with the addition of extra slots at the antenna back-face metallization. The radiation pattern and polarization are very stable over the entire UWB. Link measurements between two identical antennas demonstrate low pulse distortion over almost all the solid angle

Passive UHF RFID Tag for Airport Suitcase Tracking and Identification

A passive UHF tag configuration is presented for suitcase identification and tracking in airport handling applications. The proposed tag antenna solution is based on a conformal geometry, consisting of a folded dipole with orthogonal arms, appropriate for integration into the wall of injection moulded suitcases during its fabrication process. The tag antenna is designed for the ALIEN Higgs-2 integrated circuit. Simulated frequency dependence of the proposed UHF passive tag shows adequate performance across the world UHF RFID bands. Maximum tag detection range as well as detection isotropy were measured in several test environments both for a prototype tag attached to a suitcase and for a tag embedded in the suitcase wall. Full detection of the embedded tag was obtained for all suitcase orientations in the tested scenarios

Performance of a crossed exponentially tapered slot antenna for UWB systems

WOS:000265937400006 (Nº de Acesso Web of Science)A compact printed antenna is described that exhibits adequate transient performance for ultrawideband (UWB) applications and it is further adequate for polarization diversity schemes. The antenna is based on an original combination of two crossed exponentially tapered slots plus a star-shaped slot to produce a stable radiation pattern with very stable polarization over the 3.1-10.6 GHz FCC assigned band. Results are confirmed with measurements. Figures of merit like output pulse fidelity and time window containing 90% of the transmitted energy are analyzed over the entire solid angle and showed to remain quite stable, in line with envisaged UWB system requirements. Compact dual-antenna arrangements are also analyzed in view of potential use for UWB multiple-input-multiple-output implementations

RFID smart shelf with confined detection volume at UHF

WOS:000269791600065 (Nº de Acesso Web of Science)This letter presents a smart shelf configuration for radio frequency identification (RFID) application. The proposed shelf has an embedded leaking microstrip transmission line with extended ground plane. This structure, when connected to an RFID reader, allows detecting tagged objects in close proximity with proper field confinement to avoid undesired reading of neighboring shelves. The working frequency band covers simultaneously the three world assigned RFID subbands at ultrahigh frequency (UHF). The concept is explored by full-wave simulations and it is validated with thorough experimental tests