Lauri Sydänheimo

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.

A small planar inverted-F antenna for wearable applications

Small printed antennas will replace the commonly used normal-mode helical antennas of mobile handsets and systems in the future. This paper presents a novel small planar inverted-F antenna (PIFA) which is a common PIFA in which a U-shaped slot is etched to form a dual band operation for wearable and ubiquitous computing equipment. Health issues are considered in selecting suitable antenna topology and the placement of the antenna. Various applications are presented while the paper mainly discusses about the GSM applications.

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.

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...

Printed humidity sensor for UHF RFID systems

This paper presents a printable humidity sensor for RFID systems at UHF frequencies. The sensor is printed onto Kapton HN polyimide substrate using silver ink. The sensor measures humidity capacitively through the permittivity change in the polyimide. The actual measurement result is acquired from the tag using a threshold power sweep performed by the reader device. The operation principle is explained and simulation results are shown. Simulation results predict good sensor performance and thus the sensor is ready for the prototype stage.

Read Range Performance Comparison of Compact Reader Antennas for a Handheld UHF RFID Reader

Handheld radio frequency identification (RFID) reader units become increasingly important with the adoption of passive ultra-high frequency (UHF) RFID systems in supply chain, warehouse and retail store management. Important requirements for the handheld reader unit are ergonomic size and weight, sufficient battery life and suitable read range for the desired applications. In addition, usability of the reader unit in terms of reading directions and orientations of tags has to be taken into account. This paper presents a performance comparison of compact reader antennas for a handheld UHF RFID reader unit. The reader antennas presented in this study are designed to be affixed either inside the casing of the reader unit or into an external reader antenna module. The presented antenna designs have been optimized with finite element method (FEM) modeling. The resonance frequency and bandwidth characteristics are analyzed using modeled and measured results. Read range measurement results with the antenna designs affixed to the handheld reader are presented and analyzed to verify the practical performance. All the antenna designs presented in this paper are applicable to a handheld RFID reader unit.