The analysis and experimental verification of the properties of four types of chipless RFID tags with increased RCS response level designed and fabricated by conductive screen printing by silver paste on foil and paper substrates was performed. The analytical formula for the quality factor of microstrip structures with reduced conductivity of metal layers was used to predict the changes and detectability of the backscattered RCS response. The analysis provides insight into the limitations and outlines the possibilities of chipless structures screen-printed on foil and pa-per substrates, which can be of significant benefit to further reduce the cost and speed up the production of these tags for identification and sensing purposes.
Harmonic Balance/Full-Wave Analysis of Wearable Harmonic Transponder for IoT Applications
The paper presents a novel design of a compact wearable harmonic transponder with double-plane symmetry, composed of a dual-band patch-type antenna loaded by an HSMS-2820 Schottky diode, operated as a proof-of-concept at ISM UHF 869 MHz and 1 734 MHz frequencies. The antenna is analyzed and optimized for a minimum ground plate size by means of the CST Microwave Studio electromagnetic simulator, and its reflection coefficient is incorporated into the equivalent circuit model for a combined harmonic balance and full-wave analysis using the AWR Microwave Office commercial simulator. The transponder performance, including the complex input impedance matching and conversion loss (CL) between the fundamental and second harmonic frequencies on the diode, was evaluated both in free space and when attached to a human muscle phantom. The total harmonic transponder CL, including diode CL, antenna transponder gains, and impedance mismatching, is 6.2 dB for an excitation power of −25 dBm at the antenna–diode interface. The measured reading distances are 9.0 m and 8.8 m for EIRP = 20 dBm when the transponder is placed in free space and on the human body, respectively. As a means of machine-to-person communication, the transponder is suitable for Internet-of-Things concept, e.g., for the identification of pedestrians in traffic, i.e., in a complex environment with unwanted radiation clutter and multipath fading.
Proof of Concept of Reconfigurable Solvent Vapor Sensor Tag with Wireless Power Transfer for IoT Applications
In this paper, a concept of reconfigurable chipless Radio Frequency Identification (RFID) sensor tag for detecting solvent vapors/gas in IoT applications was presented. The concept is based on authors previously published rectangular loop structure equipped with a U-folded dipole loaded with a glide-symmetrical interdigital capacitor coated with a thin layer of tetrasulfonated copper phthalocyanine deposited as a sensing layer to improve the sensing capability in the presence of acetone vapor. In order to further maximize the sensitivity of the designed structure to the de-sired solvent, a circuit for a central frequency adjust using a radio frequency varactor diode bi-ased with a wireless power transfer (WPT) was designed. By varying the DC bias of the diode, a continuous tunable range of approximately 200 MHz was achieved. The proposed reconfigurable wireless sensor tag was manufactured and the frequency shift was verified by measurement. The proposed external frequency control can be applied to a wide class of electrical resonators.
Remote Tuning of Resonant Circuits Using Wireless Power Transfer
The resonant frequency of a solvent vapor sensor tag has been made adjustable through the use of a RF varactor diode biased using wireless power transfer. Varying the DC bias of the diode provided a continuous tuning range of about 200 MHz. The proposed external frequency control can be applied to a wide class of electric resonators used in passive systems without an energy source. The proposed reconfigurable wireless resonant circuit was manufactured and the measured results agree well with the simulations.
Wearable Harmonic Transponder for IoT Applications
The paper presents a novel compact wearable harmonic transponder, composed of a dual-band patch-type antenna loaded by an HSMS-2820 Schottky diode, operated at 869 MHz and 1 734 MHz frequencies. The antenna itself is optimized for a minimum ground plate size. The transponder performance was evaluated both in free space and when attached to a human muscle phantom. The total harmonic transponder conversion loss is 6.2 dB for an excitation power of −25 dBm at the antenna–diode interface, outperforming state-of-the art solutions. The measured reading distances are 9.0 m and 8.8 m for EIRP = 20 dBm when the transponder is placed in free space and on the human body, respectively. As a means of machine-to-person communication, the transponder is suitable for Internet-of-Things concept.
Chipless RFID Tag with Enhanced RCS Used as a Phthalocyanine-Based Solvent Vapors Sensor
A novel uniplanar chipless RFID solvent vapors/gas sensor is proposed in this paper. The sensor etched on an extremely thin capton substrate is composed of the folded dipole resonator loaded by the interdigital capacitor located inside the planar rectangular metallic loop that improves the RCS response. When illuminated by a plane wave, the folded dipole causes a notch in the RCS response of the loop located near its resonant frequency. The high RCS level (-18 dBsm), together with the notch depth (16 dB) assure a reliable detection of its position within the frequency dependence of RCS curve. In order to enhance the structure sensitivity to the presence of acetone vapors, the tetrasulfonated copper phthalocyanine thin film was applied as a sensitive layer during the process of folded dipole metallization. The experimental verification confirmed the viability of sensor proof-of-concept for the detection of chemical vapors.
The analysis of capacitive wireless power transfer was conducted in a general manner. The circuit model of a capacitive wireless power transfer chain was presented. The derivation of the power transfer efficiency through the chain in question as well as the active power delivered to the appliance terminating this chain was shown. Both the case of the maximal efficiency and the one of the maximal appliance power were treated and conditions for these optima were found in both cases. The appliance power corresponding to the maximal efficiency and the efficiency corresponding to the maximal appliance power were also expressed. The total admittance of the capacitive wireless power transfer chain was calculated. For both optimal conditions, the appliance power and total admittance were written in the normalized form, which enabled to express them as functions of single variable in the same way as the efficiency.
High-Performance Chipless Radio-Frequency Identification Tags: Using a Slow-Wave Approach for Miniaturized Structure
A novel planar chipless radio frequency identification (RFID) tag is introduced in this paper. The tag is composed of miniaturized multiple reflecting antennas based on a slow wave structure. To validate the proposed approach, a tag with a coding capacity of 16 bits has been designed with a compact size of 15 × 21 mm². Tags with different pattern configurations have been performed using a Rogers RO4003 substrate and its radar cross-section responses have been measured. Compared to conventional multi-resonator tags, the proposed tag offers a good miniaturization ratio and spectral coding efficiency. In addition, the measurements revealed high Q factor and coding robustness which demonstrates the efficiency of the used approach to develop high performance chipless tags.
Platform Tolerant, High Encoding Capacity Dipole Array-Plate Chipless RFID Tags
In this paper, we first carry out an in-depth review of the performance parameters of frequency domain chipless RFID transponders in terms of their spatial density, spectral capacity, and comprehensive encoding capacity (bit/lambda2/GHz) comprising both spatial and spectral performance, and platform tolerance. Secondly, we theoretically and numerically investigate the recently introduced and promising concept of the platform-tolerant chipless RFID transponder based on a detuned dipole array-plate that provides high encoding capacity. We propose, fabricate and measure a 20-bit transponder consisting of an array of 20 detuned dipoles closely coupled to a 60 × 60 mm2 metallic plate. The radar cross section at the level of 15 dBsm exhibits reliably recognizable minima corresponding to individual dipole resonances. When compared to other published frequency-domain chipless RFID transponders, the encoding capacity reaches 47.4 bit/lambda2/GHz, which constitutes one of the highest values, while achieving a concurrently high level of radar cross section (RCS) reflection response and platform tolerance performance. The measurements confirm very good performance parameters in the cases when the transponder is attached to various packaging materials, such as cardboard, plastic, wood, metal or a human body phantom. The essential benefits of the presented solution include a very good frequency and amplitude stability in the RCS response, which enables a reliable reading of encoded information (if zero bits are coded). The double layer metallization represents an inherent property of the proposed solution, which is a necessary trade-off for high encoding capacity and contemporary platform tolerance.
Power Balance of Capacitive Wireless Power Transfer
The power balance analysis of the capacitive wireless power transfer was conducted in a general manner. The circuit model of a capacitive wireless power transfer chain was presented. The derivation of the power transfer efficiency through the chain in question as well as the active power delivered to the appliance terminating this chain was shown. The case of the maximal efficiency was treated and conditions for this optimum were found. The appliance power corresponding to the maximal efficiency was also expressed. For the optimal conditions, the appliance power was written in the normalized form, which enabled to express it as a function of single variable in the same way as the efficiency.
Scalar Method for Reading of Chipless RFID Tags Based on Limited Ground Plane Backed Dipole Resonator Array
In this paper, we propose a novel frequency domain reading method for the chipless RFID tags. It is based on a single scalar measurement of transmission coefficient magnitude between two antennas by the presence of a tag. The method enables to reliably read the chipless RFID tags based on a dipole resonator array, which is backed by a limited ground plane, in a real environment outside the anechoic chamber. Moreover, it suits simple, yet not necessarily well impedance matched, reader antennas represented by an open end of the rectangular waveguide. The method was verified experimentally in the frequency band of 7–11 GHz.
UHF RFID zářiče pro činnost v blízkosti lidského těla
Příspěvek shrnuje současný stav technologie bezkontaktní identifikace (RFID) v UHF a dalších mikrovlnných kmitočtových pásmech především se zaměřením na chování antén transpondérů v blízkosti ztrátových objektů jakými je např. lidské tělo. V neposlední řadě představuje současné trendy ve vývoji těchto systémů, jakými jsou bezčipová bezkontaktní identifikace a bezkontaktní identifikace ve spojení se senzorickou funkcí.
Elektromagnetické vlastnosti UHF RFID zářičů v blízkosti lidského těla
Příspěvek se zabývá bezkontaktní identifikací (RFID) osob v UHF a dalších mikrovlnných kmitočtových pásmech. Zaměřuje se především na problematiku antén transpondérů umožňujících spolehlivou funkci v těsné blízkosti lidského těla nebo jiných vodivých a dielektrických objektů. V neposlední řadě představuje současné trendy ve vývoji těchto systémů, jako jsou bezčipová RFID, spojení RFID se senzory, apod.
Frequency-Domain Chipless RFID Transponders: Improvement the Reading Response
This paper reviews investigations of the authors in the field of frequency-domain chipless RFID transponders. The main issue is to reduce the mutual coupling between adjacent resonant elements in the scatterer array to ensure the robust RCS response for reliable reading of coded information. A major improvement in RCS response of transponders is proposed, using slot-in-plate type transponders. Advantages and drawbacks of the proposed solutions are discussed and several open challenges in the field are emphasized.
Influence of Mutual Coupling on Stability of RCS Response in Chipless RFID
The paper investigates the influence of mutual coupling between individual scatterings of chipless Radio Frequency Identification (RFID) tags based on its frequency-domain performance using a simplified equivalent circuit model. The proposed steady state analysis predicts a fast and satisfactory amplitude level and frequency position of resonant peaks of a predicted radar cross section (RCS) response. The proposed approach is capable of pre-evaluating a suitability of the particular scattered topology for implementing in chipless RFID tags. It is demonstrated on two different geometries.
Polarisation Independent Chipless RFID Tag Based on Circular Arrangement of Dual-Spiral Capacitively-Loaded Dipoles with Robust RCS Response
The paper deals with the novel polarisation independent 20-bit chipless RFID transponder that is based on a circularly arranged array of electrically small dual-spiral capacitively-loaded dipole scatterers with improved robustness of RCS response. A single scatterer exhibits a better performance in terms of electrical size and radar cross section (RCS) than the earlier introduced U-dipole type scatterers occupying the same footprint area. In order to investigate the frequency stability and amplitude uniformity of RCS curve, two arrangements of scatterer arrays were analyzed: rearranged side-by-side and circular. In comparison to the other arrangements, the latter provides an excellent amplitude RCS stability over the whole operational frequency band and, at the same time enables the polarization independence of identification. However, it requires the two-channel orthogonal polarization measurement.
Reliability Improvement of RF Identification of Shadowed People in Building Corridors Using Space Diversity
This paper deals with the investigation of space diversity techniques for elimination of signal fading and consequently extension of coverage area in applications of RF identification of shadowed people in a building corridor. Several measurement scenarios were evaluated. They comprised up to four wearable tags placed at different positions on a human body with one or two reader antennas, including shadowing by a small crowd of people. It was shown that the achieved corresponding SIMO mode diversity gain accounted for ca. 1 dB at the overall improvement in the trace coverage amounted to ca. 5%. On the other hand, the MIMO mode diversity configuration brought an improvement of up to 10% and enabled to cover more than 50% of the identification area, including the scenario where shadowing by a small crowd of people was present.
Semi-Platform Tolerant 20-bit Chipless RFID Tag Composed of Dipole Array Closely Coupled to Plate
In this paper novel semi-platform tolerant 20-bits chipless RFID tag based on array of dipoles closely coupled to metallic plate of the size 60 × 60 mm is presented. Quality factor of single dipole-plate is analysed to better understand the resonant behavior of the scatterer. RCS response level about 15 dBsm, spectral bit capacity > 15 bit/GHz and good frequency and amplitude stability of the RCS represent promising solution for chipless RFID systems.
Chipless RFID Tag Based on Electrically Small Spiral Capacitively Loaded Dipole
The paper presents the novel 20-bit chipless RFID transponder (tag) based on spiral capacitively loaded dipole scatterers of electrical size ka = 0.47, radar cross section σ = 29.3 dBsm, and bandwidth BW3dB = 20.9 MHz. It outperforms U-folded dipole scatterer (ka = 0.79, σ = 34.3 dBsm, BW3dB = 18.1 MHz) in the first two parameters in exchange for a slight increase in bandwidth. The total tag size (17 × 68 mm2) is roughly half the size of a credit card. The frequency and amplitude stability of its RCS response, when the zero bit information is coded via removal of individual scatterers, is improved by reordering scatterers in the array. The simulated results were verified by the monostatic measurement of tag RCS.
Chipless RFID Tag with an Improved Magnitude and Robustness of RCS Response
This paper describes properties of a new 20-bit chipless RFID tag of the size 52 × 50 mm2, which exhibits an improved magnitude and robustness of the radar cross section (RCS). The tag is based on a novel slots-in-plate array approach, which is complementary to a typical tag consisting of an array of single resonators. In order to eliminate the detuning effect of the missing or shortening slots representing ‘0’ bit information on the resonances of neighbouring slots signifying ‘1’ bit information, the modification of the inter-element arrangement was proposed. Both ways of ‘0’ bit information coding were studied and compared.
Compact UWB MIMO Antenna with Asymmetric Coplanar Strip Feeding Configuration
compact UWB MIMO antenna composed of two elements is presented in this paper. The two antenna elements are fed by asymmetric coplanar strip (ACS). The radiator of the single antenna consists of half elliptical shape radiator. The two antenna elements are located side by side on FR4 substrate with size equal to 48 × 28 mm2. The edge to edge distance between the antenna elements is 0.23 λ0 at 3 GHz. The two antenna elements are designed to operate in the UWB frequency band from 3 GHz to 11.5 GHz with return loss lower than -10 dB and isolation lower than -15 dB without using decoupling structures between the elements. The envelope correlation coefficient, diversity gain, and
capacity loss which define the performance of MIMO antenna are within the required limits. The proposed antennas has been fabricated and measured. Experimental measurements were obtained and are in good agreement with simulation results, which
verify that the proposed antenna is a good candidate for UWB MIMO applications. Moreover, the performance of the MIMO antenna is verified by computing the envelope correlation coefficient (ECC), diversity gain (DG), and channel capacity loss (CCL).
Design and Measurement of a Compact UWB MIMO Antenna With Asymmetric Coplanar Strip Feed
Proceedings of International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting. Piscataway, NJ: IEEE, 2017. p. 1655-1656. ISSN 1947-1491. ISBN 978-1-5386-3284-0.
This paper presents the design and measurement of a two-element MIMO antenna for UWB applications. Feeding for the MIMO antenna is employed using Asymmetric Coplanar Strip (ACS). The two elements are printed side-byside on FR4 substrate, without having to use a decoupling structure between the two antennas. The edge-to-edge separation distance is 0.230 at 3 GHz. The proposed antenna operates in the UWB band from 3 GHz to 11.5 GHz, with a reflection coefficient below -10dB and insertion loss less than - 15dB. The envelope correlation coefficient is under the allowed limits of MIMO systems. The proposed two-element MIMO antenna has been fabricated and measured. Measurement results agree with the simulation results, which verifies the use of the proposed antenna for UWB applications.
Detuned Dipole Array Backed by Rectangular Plate Applied as Chipless RFID Tag
A chipless RFID tag designed as detuned dipole array backed by rectangular plate is proposed. Its main feature is frequency notched RCS response which provides high read range of the tag. Information encoding ability was investigated on three example bit words. It has been found that proposed structure exhibits narrow resonances with higher bit density than other presented structures and thus seems to be a good candidate for compact high density chipless RFID tags. Performance parameters of the structure has been evaluated by EM simulator Zeland IE3D and verified by monostatic measurement in an anechoic chamber.
Erroneous Reading of Information in Chipless RFID Tags
Chipless RFID tags are designed as arrays of planar or uniplanar resonators. These tags should be as small as possible to increase their attraction. On the other hand the closer are particular resonators located the tighter is their coupling. This coupling prevents the reader from proper reading the coded information. This is due to detuning of particular resonant frequencies of resonators and due to changing levels of the resonant peaks. Finally some compromise must be done in the tag design. For error-less reading of information coded by the presence/absence of resonant peaks in the RCS response the proper choice of scatterer topology and their arrangement has significant importance. Simple and efficient way of checking the suitability of particular resonators is presented.
Europe and the Future for WPT COST Action IC1301 Team
This article presents recent European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to highpower electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301 (Table 1). WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions.
A Comparison of Two Ways to Reducing the Mutual Coupling of Chipless RFID Tag Scatterers
This paper presents two ways to reduce the mutual coupling between the resonators of the RFID chipless tags. This reduction significantly improves the uniformity of the RCS response of the tag over the operational frequency range from 2 to 4 GHz. The first modification to the tag layout is based on an inter-element rearrangement of the array elements. The second layout modification is based on narrowing the strip width and tapering the longitudinal dipole arms toward the open end. Significantly improved homogeneity of the RCS response in comparison with the original array of folded dipole scatterers was confirmed by simulation and by measurements of 20-bit chipless RFID transponders. The second modification further improves the frequency resolution, which may consequently provide higher encoding capacity in a unit area, but at the expense of a decreased RCS response.
Bezčipová identifikace na radiových kmitočtech (RFID)
Tématem tohoto příspěvku je bezčipová identifikace na rádiových kmitočtech (chipless RFID). Technologie RFID přináší v posledních letech vyšší úroveň automatizace, která se uplatňuje především v logistice, průmyslu a maloobchodu. Využití však nachází také v medicíně, v knihovnictví a při inventarizaci majetku obecně. Další rozšíření RFID (zejména pro náhradu čárových kódů) závisí na tom, zda se podaří tuto technologii dále zlevnit. Jako řešení tohoto problému se nabízí odstranění nejnákladnější části identifikačního štítku (tagu), kterou je polovodičový čip. Tento příspěvek přináší přehled různých bezčipových řešení.
Capacitively Loaded Dipoles for Chipless RFID Transponder
This paper proposes a novel uniplanar capacitively loaded dipole-scatterers as building elements for chipless RFID tags with frequency domain coding information. These elements are compared with the known structures in terms of quantities which are crucial for read range (radar cross-section), coding bit capacity (resonance bandwidth), and electrical size. Most suitable type of scatterer was arranged into a 5-bit tag, manufactured and verified by measurement in anechoic chamber.
Implantable Semi-Active UHF RFID Tag With Inductive Wireless Power Transfer
The objective of this paper was to design a compact, battery-less system for an implantable semi-active UHF RFID tag with inductive wireless power transfer for the human body. An RFID chip of the tag, combining powering from a reader by communication and from another source through inductive wireless power transfer, was used. Tag sensitivity for communication was increased by about 21 dB with the help of wireless inductive powering when compared to tags which did not employ this system. Communication and powering circuits were integrated within compact structures on the sides of the reader and the tag. The structure for communication and powering on the side of the reader consists of a centre-excised Archimedes spiral antenna and a circular loop respectively. Similarly, the structure on the side of the tag consists of a folded dipole antenna for communication and a rectangular loop for powering.
Improvement in Robustness and Recognizability of RCS Response of U Shaped Strip-Based Chipless RFID Tags
The paper presents significant improvement in robustness and recognizability of RCS response of the two topologicaly rearranged 20-bit U-shaped strip-based tags for spectral signature-based chipless RFID systems. The space rearrangement of individual tag scatterers in the array reduces the inter-element mutual coupling and thus significantly enhances the frequency and amplitude robustness of their radar cross section (RCS). In comparison to the original arrangement of scatterers, the measurement of tags designed for 2 to 4 GHz frequency band showed a significantly improved homogeneity of the RCS curve which results in a more reliable recognition of coded information.
Improvement of Reading Performance of Frequency Domain Chipless RFID Transponders
This review paper presents the summary of our investigations in several topics of frequency-domain chipless RFID transponders. The performance comparison of various types of scatterers used in the literature and recently proposed by the authors is presented. The issue of proper location of adjacent resonant elements in the scatterer array to reduce the mutual coupling and consequently ensure the robust RCS response for reliable reading of coded information is addressed. A major improvement in RCS response of transponders is proposed, using slot-in-plate type transponders. Advantages and drawbacks of the proposed solutions are discussed and several open challenges in the field are emphasized.
Inductive Wireless Power Transfer for Human Body Implantable UHF RFID Tag
This contribution deals with a design of a system with RFID communication and inductive wireless powering for a human body implantable tag. A chip of the tag employs powering from an RFID reader by communication and from another source with the help of inductive wireless power transfer. Circuits for communication and powering on the reader and tag sides were designed as compact planar structures. The reader side structure comprises a centre-excised Archimedes spiral antenna for communication and a circular loop for powering. The tag side structure integrates a folded dipole antenna for communication and a rectangular loop for powering. The communication sensitivity of the tag was increased by about 21 dB when the additional inductive wireless powering was used.
On-body semi-electrically-small tag antenna for ultra high frequency radio-frequency identification platform-tolerant applications
In this study, the authors proposed the impedance-flexible on-body semi-electrically-small tag antenna for the European ultra-high frequency radio-frequency identification (UHF RFID) frequency band. The radiator is based on differentially-fed coupled shorted-patches and vertical folding techniques, using a loop excitation. The proposed excitation methods enable the input impedance to be tuned to the complex impedance of typical UHF RFID chips as well as to 50 Ω impedance. In addition, the virtual electric short applied inside the structure simplifies the topology and manufacture. The antenna dimensions are 40 × 50 × 3 mm3 (0.12 × 0.14 × 0.01 λ 0) and represent the electrical size ka = 0.58 at 866 MHz. The total efficiency measured in open space exceeds 60%. In case that the antenna is situated on a human phantom, it accounts for 50%. Accordingly, the antenna provides the read range of 5.6 m (in open space) and 5.1 m (when located on human chest).
Reducing Mutual Coupling in Chipless RFID Tags Composed of U-Folded Dipole Scatterers
We propose a novel chipless RFID tag composed of topologically modified uniplanar U-folded dipoles with inclined arms. This topology reduces the interelement mutual coupling and provides a significantly better amplitude uniformity and frequency stability of tag RCS response when logical “0” is coded by removing particular scatterers from the array. Simultaneously, it provides a higher encoding capacity in unit frequency range than the arrays composed of original U-folded dipoles with parallel arms, yet at the expense of small RCS magnitude reduction.
Semi-Active 866 MHz RFID Implantable Tag Fed by 6.78 MHz Inductive Wireless Power Transfer
The paper presents a compact battery-less semi-active UHF RFID tag powered by an inductive wireless power transfer designed to be implanted into the human body. Communication runs at frequency of 866 MHz whereas powering is performed at frequency of 6.78 MHz to reduce losses. Tag sensitivity for communication was increased by about 21 dB with the help of inductive wireless powering when compared to a tag which did not employ this powering. Communication and powering circuits were integrated within compact structures on the sides of the reader and the tag. The reader side consists of a center-excised Archimedes spiral antenna for communication and a circular loop for powering. The tag side consists of a folded dipole antenna for communication and a rectangular loop for powering.
Improvement of RCS Response of U Shaped Strip Based Chipless RFID Tags
We present a modification of an arrangement of 20-bit chipless tag composed of 20-element array of U-shaped strip scatterers that significantly improves radar cross section response in terms of uniformity and amplitude robustness over the operational frequency range 2 to 4 GHz. This modification is based on the inter-arrangement of array elements in order to eliminate the strong coupling between neighboring resonance elements. The tag has been measured in a mono-static arrangement with one double-ridge horn antenna, and provides a significantly improved homogeneity of the RCS response compared to an original array of folded dipole resonators. The reliability of the reading of coded information is highly improved
Matching Technique for an On-Body Low-Profile Coupled-Patches UHF RFID Tag and for Sensor Antennas
The paper introduces a novel impedance matching technique for extremely low-profile on-body UHF RFID tag antennas based on coupled shorted-patch antennas. The approach employs a novel arrangement of comb-notches perpendicular to the central radiation slot that excites the close higher order mode that affects the field distribution of the fundamental mode and sets the input impedance to the required complex values of UHF RFID chips over the range of 5 to 50 for the real part and 100 to 200 for the imaginary part, or directly to 50 impedance. A set of parametric studies shows the flexibility of the proposed technique for achieving complex input impedances. To verify the proposed technique, we have developed and measured two antenna samples of relative size 0.3 × 0.17 × 0.0022 λ0. A first antenna is matched to 50 , and is intended to be used as an on-body antenna sensor for mapping the received signal strength in applications of the European UHF RFID band. The second antenna operates as an RFID tag antenna with input impedance Zin = 22 + j195, and reaches a read range of 7.3 m.
Stepped Impedance Coupled-Patches Tag Antenna for Platform-Tolerant UHF RFID Applications
We introduce a low-profile platform-tolerant UHF RFID tag antenna composed of a pair of three-step impedance sections of shorted-patches coupled by a slot, which is differentially fed by an RFID chip. Its input impedance is analytically investigated using transmission line modeling. A further set of parametric studies using electromagnetic simulation shows good flexibility for achieving the required complex input impedance for typical UHF RFID chips. The selected antenna topology has been manufactured and measured, and good agreement with the analytical values has been found.
This paper introduces a new 20-bit chipless RFID tag with an improved radar cross section (RCS), based on a novel complementary approach with the slot-in-plate array with respect to the array of single resonator-based chipless tags. The backscatter pattern is formed by a rectangular metallic plate 52 × 50 mm2 in size etched on a thin dielectric substrate in which an array of 20 shorted coplanar slots is introduced. The originally monotonous RCS frequency response of the rectangular plate exhibits dips corresponding to the presence of individual slots, and thus enables binary coding using amplitude shift keying. The tag has been measured in a bi-static arrangement with two double-ridge horn antennas, and provides a significantly improved overall RCS response compared to an array of resonator-based chipless tags. We also propose two modifications to the inter-arrangement of the slots in order to eliminate the detuning effect of the missing slot representing ‘0’ bit information on the resonances of neighboring slots representing ‘1’ bit information.
Illustration of the Impedance Behaviour of Extremely Low Profile Coupled Shorted-Patches Antennas for UHF RFID of People
The recently introduced coupled shorted-patches technique for the design of extremely low-profile UHF RFID tag antennas is used to illustrate the flexibility of selected feeding methods for tuning the antenna input impedance for the complex values required for matching with typical RFID chips. We present parametric studies of the impedance behaviour of dipole-excited and directly excited antennas designed for radiofrequency identification of people in the European UHF frequency band. Our study can significantly facilitate the design of this class of on-body tag antennas.
Small-Size Wearable High-Efficiency TAG Antenna for UHF RFID of People
This paper introduces a small-size, low-profile wearable radiator based on the coupled patches and vertically folded patches techniques for application as a tag antenna for identification of people in the European UHF RFID band. The electric field distribution comes out dominantly from the central coupling slot, and thus the electric properties of the radiator are almost unaffected by the human body to which the antenna is intended to be attached. Accordingly, with the relative size 0.14 × 0.12 × 0.009 λ0 at 866 MHz (50 × 40 × 3.04 mm3), the antenna exhibits total efficiency better than 50 %, even if it is attached directly to a person.
Impedance Properties and Radiation Efficiency of Electrically Small Double and Triple Split-Ring Antennas for UHF RFID Applications
The present paper is targeted at investigation of electrically small planar antennas, formed by double- and triplesplit rings that are intended to serve as tag antennas operated within the European UHF RFID band. An extensive systematic study of possible geometrical configurations demonstrates the range of their achievable input impedances (complex conjugate to typical UHF RFID integrated circuits) in case that both structures electrically decrease below the limit for electrically small antennas, i.e. ka < 0.5. The advantage of triple split ring version over the standard double split ring one consists in reduction in its electrical size and concurrent maintenance of the required range of input impedances and high radiation efficiency. Samples of both structures were manufactured, measured and their electrical properties critically compared.
Novel Low-Profile Foam Dielectric Over the Shoulder Antenna Based On Coupled Patches Technique
The paper presents a novel wearable antenna composed of two coupled patches excited by an overlapping folded dipole. In spite of being operated in a relatively low frequency band 380 ÷ 390 MHz, the antenna shows a very low profile and other dimensions are acceptable as well. Besides a very low absorption of the radiated RF power by any nearby human body, it also ensures a very good immunity against influence on antenna parameters. In comparison to commonly used simple conformal monopole antennas, the presented solution provides a double-side radiation pattern and a substantially higher gain. The antenna can be manufactured using very light and twistable foam dielectric and conductive fabric, and can be worn as a strap placed over the shoulder. It is intended to be used together with personal radio communication transceivers operated in the given frequency band.
Parametric Study of the Low-Profile Foam Dielectric Over-the-Shoulder Antenna Based on Coupled Patches Technique
The paper presents a parametric study of the over-the-shoulder foam dielectric antenna based on coupled patches technique for 380 ÷ 390 MHz frequency band. Despite having a very low profile (0.0072 λ0), it shows the satisfactory radiation efficiency and very good immunity from the negative influences of the human body. Influence of the antenna elements to the radiation efficiency, gain, frequency bandwith and impedance matching is
evaluated by means of the parametric study.
Detection of Spiral Resonator Array for Chipless RFID
Presented paper analyzes the influence of different
configurations of the planar resonator arrays of the size 16×4 up
to 16×16 elements on the reflection coefficient of the halfwavelength
dipole probe in the frequency range 600-1000 MHz.
Four different square spiral resonators of the outer diameter
7 mm (~ 0.02λ0@800 MHz) with various total lengths of the
conductor are used as array building elements. It is shown that
specific arrangement of the resonators in the array enhances the
response of the probe. The work was motivated by the potencial
application of such arrays in chipless RFID technology.
Active UHF Antennas for Demanding RFID Applications
One of possible applications of RFID systems concerns identification of goods equipped with TAGs, densely and randomly accommodated in a larger space. This refers e.g. to the identification of many TAGs fixed on clothes in large cartoon boxes. The TAGs can be located very close to each other, mutually coupled, screened, randomly oriented and placed in an environment with a wide range of wave propagation parameters. The presented paper describes one of the possible solutions. The designed identification system is equipped with active reader antennas that enable the illumination and the read-out of the TAGs from many different locations as well as angles, and with a wide range of illuminating power. According to preliminary measurements, such conditions conduce to 100% correct and reliable identification. The designed RFID system is very likely to be able to work well even in more demanding identification tasks.
Extremely Low Profile UHF RFID TAG Antennas for Identification of People
Three prototypes of the very low-profile TAG
antennas for UHF RFID of people were designed, as result of the
long-term development. Their performance properties from the
wearability point of view were step-by-step improved. The height
were decreased from 1.82 to 0.76 mm (0.0022 λ0 at 869 MHz).
The weight were decreased from 38 to 10 g. The gain of antennas
measured with enclosed human phantom is in the range of
0.6 ÷ 1.6 dBi. Identification range in real conditions in 4 and 2 m
wide buildings corridors reaches 7 and 17 m, respectively, with
the NXP Semiconductors chip with the sensitivity of -14 dBm.
Horizontal Five-arm folded dipole over metal screening plane for UHF RFID of Dielectric objects
The paper is concerned with the extremely low-profile foam dielectric five-arm folded dipole antenna which was developed and manufactured. The aforementioned antenna is situated on the metal screening plane and is used for UHF RFID of dielectric objects. It is designed with a complex input impedance Zin = 22 + j195 Ohm at 866 MHz. Its efficiency was evaluated by Wheeler cap method with and without enclosed a human body phantom - it accounts for approx. 40 %, irrespective of whether the phantom is enclosed or not. The preliminary test of the identification range in buildings corridor was performed. The identification range reaches as far as 15.8 m.
New Materials for Antenna Technology - Low Profile Antennas for UHF RFID of People
Novel type of extremely low-profile low-dielectric constant substrate antenna, based on two-element slot-coupled shorted-patch structure for UHF RFID applications has been developed. We use two different methods for tuning the complex input impedance ? dipole excitation and direct excitation with tuning slots. Both credit card-sized antennas exhibit the antenna efficiency better than approx. 50 %, irrespective of whether they are placed in free space or enclosed to either metallic or human body.
Two Novel Extremely Low-Profile Slot-Coupled Two-Element Patch Antennas for UHF RFID of People
Novel type of extremely low-profile low-dielectric constant substrate antenna, based on two-element slot-coupled shorted-patch structure for UHF RFID applications has been developed. We use two different methods for tuning the complex input impedance - dipole excitation and direct excitation with tuning slots. Both credit card-sized antennas exhibit the antenna efficiency better than approx. 50 %, irrespective of whether they are placed in free space or enclosed to either metallic or human body.
Microwave Radar Sensors for Active Defense Systems
Modern anti-armor missiles represent enormous
threat for any military vehicle. Simple hand-held missiles are
able to penetrate 300 mm, more sophisticated missiles up to
1000 mm of the best steel armors. Active defense methods seem
to be promising ways how to face this problem. Systems of active
defense are based on sensors able to detect and measure
approaching threat missile and generate signals that activate a suitable counter-measure. The paper describes several different
designed radar sensors tested in active defense configurations.
This concerns narrowband sector sensor, "microwave curtain"
and a new wideband sensor with a distance measurement
capability. All practical tests were performed using real missiles
at army shooting ranges.
Novel Dual-loop antenna Placed over Patch Array Surface for UHF RFID of Dielectric and Metallic Objects
Novel electrically small low-profile dual-loop antenna
over artificial-like surface, formed by four-element sub-wavelength
patch array printed on grounded dielectric slab used for shielding in
UHF RFID applications, has been developed. The badge-sized
antenna exhibits the gain of about 1 dBi and antenna efficiency
amounting to approx. 30 - 40 % whether it is placed in free space or
enclosed to dielectric/metallic objects.
UHF RFID read range tests have been performed with a novel electrically small low-profile TAG antenna equipped with an artificial-like surfaces providing very good immunity against the influence of a near human body. The RFID system equipped with this antenna has been tested for the detection of a person in indoor and outdoor areas within 869 MHz band and reached read range up to 9 m.
UHF RF Identification of People in Indoor and Open Areas
UHF RFID read range tests have been performed with a novel electrically small low-profile TAG antenna equipped with artificial-like surfaces providing very good immunity against the influence of a near human body. The RFID system equipped with this antenna has been tested for the detection of a person in indoor and outdoor areas within 869 MHz band and reached read range up to 9 and 16 m, respectively.
The book chapter is focused on radiofrequency identification of people: review, design and measurement of low profile antenna types suitable for RFID of persons; modeling and measurement of received signal level both in indoor and open environments, shadowing and corresponding signal fading; optimization of identification task geometry; read range identification tests and reliability identification tests both in indoor and open spaces including one person and a group of persons moving from slow to fast.
Application of the RFID System for Identification of Moving Racers
The paper deals with possibility application of commercial RFID system Trolley Ponder for the identification of athlete in mass races. On the basis of the mathematical model and measurement of power level by means of tests antennas a optimalization of system has been performed. The purpose is an achievement of a sufficient power back up. The optimalization consists in the configuration of power level, position and tilt of antennas and choice of polarization. The consequential is the design of TAGs antenna. The system function is verified by an outdoor test. In the conclusion improvement of the system is indicated.
Efficiency Treatment of Composite Right/Left-Handed TL Zeroth-Order Resonator Antenna
Antenna efficiency of zeroth-order resonator (ZOR) antenna implemented in composite right/left-handed transmission line (CRLH TL) microstrip structure is treated by method of moment simulator IE3D. Radiation is investigated from individual portions of the antenna structure according to calculated amplitude of surface current density. Dominantly radiating regions are identified, geometrically emphasized, nad efficiency improved version of CRLH ZOR antenna is designed, realized, measured and compared with initial design. Improvement of simulation antenna efficiency from 10 to 75 % and 4x increased measured gain at design ZOR frequency has been found.
Multiple-Arm Folded Monopole Antenna Operating Extremely Close to a Conductive Plane
Horizontal multiple-arm folded monopole antenna operating extremely
close to a conductive plane (0.003 lambda) band has designed, realized
and measured. In spite of the extremely low relative antenna height
above the conductive plane intended to be used as a shielding of human
body or metallic objects antenna antenna has satisfactory radiation
efficiency and gain over 1 dBi. Antenna in dipole arrangement is
intended to be used for RFID at 869 MHz frequency.
Novel Metamaterial Cell-Based Resonator Antenna with Broadside Radiation Pattern
A novel electrically small low-profile zero-order resonator antenna in micro-coplanar TL with both-side broadside radiation pattern has been developed. Its measured radiation efficiency and gain are 54 % and 2.1 dBi, respectively. The antenna is able to provide approx. 45% size reduction compared to the patch antenna of the same resonant frequency.
Parametric Study of the Novel UHF RFID Dual-loop Antenna
Novel electricaly small low-profile dual-loop antenna over artificial-like surface formed by four-element subwavelength patch array printed on grounded dielectric slab used for shielding in UHF RFID applications has been developed. The parametric study of the antenna has been performed. The antenna exhibit the gain about 1 dBi without significant affecting by the presence of a dielectric objects placed in the close vicinity of the antenna.
Radar Sensor for Detection of Anti-Armour Missiles
The anti-armour missiles represent one of the biggest threads for
any military vehicle, both in a standard combat or e.g. during UN
humanitarian as well as peacekeeping operations. Millions of extremely
dangerous missiles, able to break-through even tank armour-plates, are
widely spread even in the world's most dangerous hot spots and geostrategic
areas. Standard lighter vehicles and helicopters alike do not have, by
themselves, any chance against them. As a result, the possibly more
efficient methods of defense against them are under scrutiny and are subject
to a continuous development. Active defense methods are based on a detection
of the thread missiles and activation of an efficient counter-measure. The
presented paper describes parameters of two most dangerous missiles and
calculates parameters decisive for their detection in microwave frequency
range. The practical measurements verify and confirm the calculated
The Design of the Multiple-Arm Folded Dipole Antenna Operating Closely Spaced to a PEC
The planar multiple-arm folded dipoles operating closely spaced to a perfect electric
conductor (PEC) plane were studied in order to find the approach for the design of
the low profile dipole type antenna with a metallic shielding applicable for the
radiofrequency identification (RFID) within 2.4 GHz band. The effect of applied
multiple-arm folded dipole technique on the input resistance, radiation and antenna
efficiency of treated dipole configurations is explored. The antenna prototype in the
monopole configuration has been realized and measured to verify its performance
Application of the UHF RFID System for the Identification of Sportsmen in Mass Races
A modification of a standard UHF RFID system for identification of sportsmen during mass races was proposed, realized and verified. The performed mathematical simulations and measurements indicated the system components that are decisive for correct identification, i.e. primarily, both the reader and the transponder (TAG) antennas, their radiation patterns, tilt and efficiency. The optimized RFID system was tested in a standard outdoor operation with several configurations of sportsmen moving with different speeds from approx. 4 km/h up to 15 km/h. The obtained final results show 100 % identification reliability.
Based on a system study of the ability to use a commercial RFID system operating in 869 MHz band for the identification of moving sportsmen , TAG antennas has been recognized as one of the most sensitive component that affect the proper function of the whole system, especially in case when TAG antenna has to operate in the close vicinity of human body. Single and dual-band weareable patch antenna to cover European (869.5 - 869.7 MHz) and US (902 - 930 MHz) RFID bands that are not affected by the presence of human body has been designed, manufactured and measured. The specifics of the design are complex conjugate input impedance to the impedance of the chip used, application of technique to extent the operating band, using of the foam dielectric and conductive cloth. The properties of
developed TAG antennas has been compared with meander dipole and patch test antennas in free space as well as in the close vicinity to the human phantom.
The Optimization of the RFID System for the Identification of Sportsmen in Mass Races
Paper deal with the optimization of a standard UHF RFID system for
usage in an identification of mass race sportsmen. Proposed
improvements has been realized and the optimized RFID system has been
tested in a standard outdoor operation, the results proved 100%