Leena Ukkonen

Effects of metallic plate size on the performance of microstrip patch-type tag antennas for passive RFID

Metallic objects are challenging for passive ultra high frequency (UHF) spectrum radio frequency identification (RFID) systems due to the effects of conductive materials on tag antenna performance. In this letter, we analyze the effects of metallic plate size on the performance of microstrip patch-type tag antennas. Microstrip patch antennas with regular ground plane and electromagnetic band gap (EBG) ground plane are studied attached to two differently sized metallic plates. Analysis is based on finite element method (FEM) simulations and practical read-range measurements.

Inkjet-Printed Humidity Sensor for Passive UHF RFID Systems

This paper presents a novel inkjet-printed humidity sensor tag for passive radio-frequency identification (RFID) systems operating at ultrahigh frequencies (UHFs). During recent years, various humidity sensors have been developed by researchers around the world for HF and UHF RFID systems. However, to our best knowledge, the humidity sensor presented in this paper is one of the first passive UHF RFID humidity sensor tags fabricated using inkjet technology. This paper describes the structure and operation principle of the sensor tag as well as discusses the method of performing humidity measurements in practice. Furthermore, measurement results are presented, which include air humidity-sensitivity characterization and tag identification performance measurements.

Chip Impedance Matching for UHF RFID Tag Antenna Design

Passive UHF RFID tag consists of a microchip attached directly to an antenna. Proper impedance match between the antenna and the chip is crucial in RFID tag design. It directly influences RFID system performance characteristics such as the range of a tag. It is known that an RFID microchip is a nonlinear load whose complex impedance in each state varies with the frequency and the input power. This paper illustrates a proper calculation of the tag power reflection coefficient for maximum power transfer by taking into account of the changing chip impedance versus frequency.

Folded dipole antenna near metal plate

The paper presents the effects on antenna parameters when an antenna is placed horizontally near a metal plate. The plate has finite size and rectangular shape. A folded dipole antenna is used and it is placed symmetrically above the plate. The FEM (finite element method) is used to simulate the dependency of antenna parameters on the size of the plate and the distance between the plate and the antenna. The presence of the metal plate, even a small one if it is at the right distance, causes very big changes in the behaviour of the antenna. The bigger the plate, especially in width, the sharper and narrower are the lobes of the radiation pattern. The antenna height defines how many lobes the radiation pattern has. A number of the antenna parameters, including impedance, directivity and front-to-back ratio, change periodically as the antenna height is increased. The resonant frequency of the antenna also changes under the influence of the metal plate.

Operability of Folded Microstrip Patch-Type Tag Antenna in the UHF RFID Bands Within 865-928 MHz

The emerging use of passive radio frequency identification (RFID) systems at ultra-high-frequency (UHF) spectrum requires application specific tag antenna designs for challenging applications. Many objects containing conductive material need novel tag antenna designs for reliable identification. The operability of folded microstrip patch-type tag antenna for objects containing conductive material is analyzed and tested within the UHF RFID bands used at the moment mainly in Europe and in North and South America. First the operability of the tag antenna design and the effects of conductive material are modeled with simulations based on finite element method (FEM). The performance of the tag antenna design affixed to a package containing metallic foil is verified with read range measurements. The results show that the antenna design is operable in both of the UHF RFID bands within 865-928 MHz

Miniature implantable and wearable on-body antennas: towards the new era of wireless body-centric systems [antenna applications corner]

Wireless body-centric sensing systems have an important role in the fields of biomedicine, personal healthcare, safety, and security. Body-centric radio-frequency identification (RFID) technology provides a wireless and maintenance-free communication link between the human body and the surroundings through wearable and implanted antennas. This enables real-time monitoring of human vital signs everywhere. Seamlessly integrated wearable and implanted miniaturized antennas thus have the potential to revolutionize the everyday life of people, and to contribute to independent living. Low-cost and low-power system solutions will make widespread use of such technology become reality. The primary target applications for this research are body-centric sensing systems and the relatively new interdisciplinary field of wireless brain-machine interface (BMI) systems. Providing a direct wireless pathway between the brain and an external device, a wireless brain-machine interface holds an enormous potential for helping people suffering from severely disabling neurological conditions to communicate and manage their everyday life more independently. In this paper, we discuss RFID-inspired wireless brain-machine interface systems. We demonstrate that mm-size loop implanted antennas are capable of efficiently coupling to an external transmitting loop antenna through an inductive link. In addition, we focus on wearable antennas based on electrically conductive textiles and threads, and present design guidelines for their use as wearable-antenna conductive elements. Overall, our results constitute an important milestone in the development of wireless brain-machine interface systems, and a new era of wireless body-centric systems.

The Effect of Conductive Ink Layer Thickness on the Functioning of Printed UHF RFID Antennas

In this study, the effect of the conductive ink layer thickness on the performance of printed ultra-high-frequency (UHF) radio-frequency identification (RFID) tag antennas was investigated. A simple quarter wave dipole tag for European UHF RFID frequencies was designed to be tested in this study. All the tags were made by using screen-printing technique. Three different thicknesses for the ink layer were used. Performance of the tags was analyzed by the measurement of threshold and backscatter power. The results show that it is possible to produce RFID tag antennas by screen printing and it is possible to optimize the tag performance by adjusting the thickness of the electrically conductive layer. The results show how the performance characteristics deteriorated when the thickness of the printed ink layer was reduced. However, it was also shown that thin ink layers can be used in some applications and cost savings can be achieved in this way. It is therefore important to recognize these effects on the performance.

A novel tag design using inverted-F antenna for radio frequency identification of metallic objects

This paper presents novel inverted-F antenna (IFA) designs for passive radio frequency identification (RFID) tag applications. These designs can be used in identifying objects that consist of metal or other conductive material. Different substrate and superstrate materials are studied and used to test their effect on the performance of the antenna designs. The antenna performance is studied by a series of finite element method (FEM) simulations. The experimental validation of the read ranges of the tag prototypes in air and attached to metal is carried out to verify the performance of the designs. The experimental tests show that read ranges between 0.5 m and 1 m can be achieved when the prototypes are attached to metal.

Planar wire-type inverted-F RFID tag antenna mountable on metallic objects

In this paper we present and discuss the development and performance of planar wire-type inverted-F antenna (IFA) for passive RFID tag applications. This antenna design is mountable on metallic objects and can be used in RFID applications. Studies in different fields of RFID and its applications and antenna performance have been carried out at Tampere University of Technology and MIT Auto-ID Lab (P. Raumonen et al., IEEE Int. Antennas and Propag. Symp., 2003; L. Ukkonen et al., Fourth Finnish Wireless Comm. Workshop, 2003; J. Waldrop et al., IEEE Int. Conf. on Comm., 2003; S. Sarma et al, Micro, IEEE, volume 21, issue 6, 2001) and other universities recently. The IFA represents the first low-profile antenna designed for passive RFID applications on metalized objects.

Embedded wireless strain sensors based on printed RFID tag

Purpose – The purpose of this paper is to develop a wireless strain sensor for measuring large strains. The sensor is based on passive ultra high‐frequency radio frequency identification (RFID) technology and it can be embedded into a variety of structures.Design/methodology/approach – Silver ink conductors and RFID tags were printed by the screen printing method on stretchable polyvinyl chloride and fabric substrates. The development of the strain‐sensitive RFID tag was based on the behavior of the selected antenna and substrate materials. Performance of the tags and the effect of mechanical strain on tag functioning were examined.Findings – The results showed that large displacements can be successfully measured wirelessly using a stretchable RFID tag as a strain‐sensitive structure. The behavior of the tag can be modified by selection of the material.Research limitations/implications – New tag designs, which are more sensitive to small levels of strain and which have a linear response will be the subje...