Gerard Zamora

Multiband Printed Monopole Antennas Loaded With OCSRRs for PANs and WLANs

Multiband printed monopole antennas loaded with open complementary split-ring resonators (OCSRRs) are presented. The OCSRRs, modeled as parallel LC resonant tanks, act as high-impedance elements at their resonance frequencies, and different effective λ/4 sections can be achieved in the monopole by placing them at proper locations. Thus, the first working frequency is related to the length of the monopole, while the additional bands are controlled by the resonance frequencies of the OCSRRs. Moreover, the proposed antennas present monopolar radiation characteristics at all the operation bands. Two prototypes are designed, manufactured and measured: 1) a single-loaded OCSRR dual-band printed monopole antenna covering the Bluetooth and IEEE 802.11a/b/g/n bands (2.40-2.48 and 5.15-5.80 GHz, respectively); and 2) a triband prototype based on the same design, but with an additional OCSRR designed to also cover the IEEE 802.11y frequency band (3.65-3.70 GHz). Both antennas are printed on a single-layer of a low-cost substrate, resulting in very compact designs.

Dual-Band UHF-RFID Tags Based on Meander-Line Antennas Loaded With Spiral Resonators

The purpose of this letter is to implement dual-band tags for ultrahigh-frequency (UHF) radio frequency identification (RFID) applications operative in Europe and the US. Since the regulated bands of UHF-RFID in Europe (867 MHz) and the US (915 MHz) are close, broadband tags might be also considered. However, it is demonstrated in this letter that the performance of dual-band tags designed to operate at the frequency bands of interest is superior to that of broadband (monoband) tags. A meander-line antenna (MLA) has been considered for tag implementation. The dual-band functionality is achieved through a perturbation method consisting of coupling an electrically small resonator [a two-turn spiral resonator (2-SR)] to the antenna. The analysis, design, and fabrication of a dual-band UHF-RFID tag has been carried out. The measured performance of the fabricated prototype is in good agreement with theory. Measured read ranges of 6 and 8 m at the European and US frequency bands, respectively, have been obtained.

Fundamental-Mode Leaky-Wave Antenna (LWA) Using Slotline and Split-Ring-Resonator (SRR)-Based Metamaterials

A new composite right/left-handed (CRLH) slotline leaky-wave antenna (LWA) is proposed. The antenna, implemented by loading a slotline with split-ring resonators (SRRs), is designed to exhibit a balanced dispersion relation, with a continuous transition between the left-handed and the right-handed bands at 2.5 GHz. Since the periodicity of the structure is much less than a wavelength, the proposed LWA belongs to the family of quasi-uniform LWAs, and it radiates from the fundamental mode (contrary to periodic LWAs). Measured and simulated radiation patterns, gain, and scanning angle are reported for a 17-cell LWA. The experimental results demonstrate the potential of the LWA to continuously radiate from backward (- 50°) to forward (+60°) scanning angles, with maximum gains of 7.1 and 11.3 dB in the left- and right-handed bands, respectively, and specular radiation patterns.

Design and Synthesis Methodology for UHF-RFID Tags Based on the T-Match Network

A new systematic methodology for the design of T-match based UHF-RFID tags is proposed. The great majority of commercial UHF-RFID tags are based on dipole antennas using a modification of a T-match network. The literature contains examples of models that describe the T-match, but they are not sufficiently accurate to synthesize the tag geometry. Using the proposed methodology, a global band UHF-RFID tag based on a folded dipole antenna and matched to the RFID integrated circuit by means of a T-match network is designed and fabricated. Very good agreement between the measured and simulated read range is achieved within the entire UHF-RFID band, which reveals that the proposed method is amenable for accurate analysis and synthesis of T-match based UHF-RFID tags.

Analysis of the Split Ring Resonator (SRR) Antenna Applied to Passive UHF-RFID Tag Design

An electrically small planar passive UHF-RFID tag based on an edge-coupled split ring resonator (EC-SRR) antenna is presented in this work. In order to explore the potentiality and limitations of the SRR antenna and to aid the tag design, an analytical study of the SRR radiation properties at its fundamental resonance is presented for the first time. Radiation resistance, efficiency, polarization, bandwidth, and impedance matching with the radio-frequency identification (RFID) application-specific integrated circuit (ASIC) are treated in the study. Based on such analysis, the tag design process is presented, and a tag prototype of size 30 mm × 30 mm (λ0/11 × λ0/11) is designed to operate in the North-American UHF-RFID band (902-928 MHz) and manufactured. The measured read range is in good agreement with the simulation and reaches 9.3 m at 911 MHz. The tag also features a mitigation of the blind spots, providing a minimum measured read range of 4.2 m.

On the Radiation Properties of Split-Ring Resonators (SRRs) at the Second Resonance

The radiation properties of split-ring resonators (SRRs) at their second resonance frequency are studied for the first time in this work. In particular, the electric and magnetic dipole moments of the edge-coupled SRR are calculated analytically under the assumption of strong coupling between the internal and external rings. Based on these results, the radiation resistance and the radiation efficiency are obtained theoretically. Electromagnetic simulations of the structure reveal that there is very good agreement with the theoretical predictions, pointing out the validity of the proposed analysis. As a proof of concept, an SRR antenna prototype is designed and fabricated. Experimental data are in good agreement with the theoretical and simulated results, and demonstrate the validity of the SRR working at its second resonance frequency as a radiating element.

An impedance matching method for optical disc-based UHF-RFID tags

An impedance matching method applicable to UHF-RFID tags mounted on optical discs, where the main radiating element is the disc metallic layer (from now on optical disc-based tags) is presented in this paper. Such a method provides a very simple analytical approach and allows us to obtain any arbitrary matching level at the desired frequency, by using only one reactive element as a matching network. As a demonstration, the method is applied to the design of a DVD;R based tag, using the Alien Higgs 3 RFID ASIC, and forcing conjugate matching at 915 MHz. The tag design and synthesis process is explained and a bandwidth optimization analysis is also provided. The validity of the method is confirmed by EM simulations and experimental measurements. The measured read range of the fabricated tag reaches 8.3 m at 915 MHz and presents 50 MHz half-power bandwidth.

Free-Space and on-Metal Dual-Band Tag for UHF-RFID Applications in Europe and USA

In this paper, we present an UHF-RFID tag mountable on metallic surfaces and capable to operate in the assigned frequency bands in Europe (866{869MHz) and USA (902{928MHz). Due to the proximity of these frequency bands, the dual-band functionality can be achieved through a perturbation method applied to a single band tag designed to operate at the intermediate frequency. The tag consists of an integrated circuit, an impedance matching network (where the perturbation method is applied) and a patch antenna. The considered antenna has been chosen because it has high e-ciency over metallic surfaces. The whole tag has been analyzed, designed and flnally fabricated. The read ranges measured in free-space are 9.5m and 7.5m at the European and USA frequency bands, respectively. By placing the tag on a metal surface, the read ranges increase up to 14m and almost 11m, respectively.

An Approach for the Design of Passive UHF-RFID Tags Mounted on Optical Discs

In this paper, an innovative design strategy for UHF-RFID tags mounted on optical discs (such as DVDs) is presented. By using the metal layer of the disc as the main radiating element, it is possible to overcome the severe limitations of the existing tags for disc identification in terms of read range and bandwidth. The design and synthesis process, based on the proposed circuit model of the tag, is described. A worldwide UHF-RFID tag prototype, for direct mounting on a DVD disc, is designed and fabricated. The measured read range demonstrates that the presented method drastically improves the performance within the whole UHF-RFID band (840-930 MHz), in comparison to the DVD tags found in the available literature.

Dual-band RFID tags based on folded dipole antennas loaded with spiral resonators

The purpose of this paper is to demonstrate the possibility of implementing folded dipole antennas operative at two closely spaced frequencies of interest, for instance, in ultra-high-frequency radio frequency identification (UHF-RFID) applications. The dual-band functionality is achieved by coupling a spiral resonator to the antenna, which operates as an unbalanced transmission line. This modifies the impedance of the antenna and dual-band functionality can be achieved by virtue of the conjugate matching between the antenna and the chip at the frequencies of interest. Two prototype devices have been designed and fabricated: a mono-band folded dipole UHF-RFID tag, and a dual-band UHF-RFID tag based on a spiral resonator coupled to a folded dipole antenna. The measured read ranges at the operating frequencies are in the vicinity of 6 m. The read ranges of the designed tags have been also measured by attaching them to different objects (a CD-ROM box and a plastic ID card). A certain frequency shift is obtained, but this shift can be corrected by merely modifying the distance between the resonator and the antenna.