Showing papers by "Toni Bjorninen published in 2011"

Inkjet-Printed Humidity Sensor for Passive UHF RFID Systems

Abstract: 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.

Embedded wireless strain sensors based on printed RFID tag

Abstract: 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...

SAR reduction and link optimization for mm-size remotely powered wireless implants using segmented loop antennas

Abstract: This paper describes an approach to reduce the average specific absorption rate (SAR) of a wireless power link for mm-size cortical implants, while decreasing the loss of the overall link by using a segmented loop transmit antenna. It further shows that, for a given receive antenna size and antenna separation, an optimum transmit antenna size-frequency pair that minimizes the link loss exists. A case study of a wireless link for a mm-size cortical implant optimized for minimum loss shows a reduction of the average SAR of more than 30 %, and a link loss improvement of approximately 10 %, leading to a 57 % increase in power available to the implant compared to a conventional loop antenna.

Temperature sensor tag for passive UHF RFID systems

Abstract: This paper presents a novel temperature sensor tag for passive UHF RFID systems and discusses a method to perform measurements in practice. The developed sensor tag is fabricated from cost-efficient and commercially available materials. Distilled water is used as the temperature sensitive material instead of the more traditional semi-conducting materials. The tag is fabricated on a FR-4 substrate which provides a rigid backing for the tag. The sensor can be constructed with a commercial passive UHF RFID IC. The temperature sensor tag's measurement range spans from a theoretical low of 0 up to over 74 °C. The read range of the tag, in free space, is over 7 metres.

Low-Profile Conformal UHF RFID Tag Antenna for Integration With Water Bottles

Abstract: Development of a low-profile and conformal RFID tag antenna with an omnidirectional radiation pattern when mounted on a water bottle is presented. The antenna design and design parameters uncertainty are quantified using numerical simulations. The simulation-based antenna design is verified experimentally for single and multiple tagged bottles configurations.

Characterization of UHF RFID tags fabricated directly on convex surfaces by pad printing.

Abstract: The possibility of pad printing in RFID tag antenna manufacturing is investigated Passive UHF RFID tags were printed on flat and on convex surfaces with two different polymer thick-film silver inks The effect of the ink and substrate material properties on tag antenna performance was examined The goal was to provide information which is needed in adapting the pad-printing technique in RFID tag manufacture The results show that pad printing is suitable for tag manufacturing on flat and on convex surfaces The curvature of the substrate did not significantly affect the tag performance It was more important to take into consideration other substrate properties, ink characteristics, morphology, and printing parameters The best practice is to take these matters into consideration in the initial tag design process to ensure proper tag performance at the desired frequency

Wireless Measurement of RFID IC Impedance

Abstract: Accurate knowledge of the input impedance of a radio-frequency identification (RFID) integrated circuit (IC) at its wake-up power is valuable as it enables the design of a performance-optimized tag for a specific IC. However, since the IC impedance is power dependent, few methods exist to measure it without advanced equipment. We propose and demonstrate a wireless method, based on electromagnetic simulation and threshold power measurement, applicable to fully assembled RFID tags, to determine the mounted IC's input impedance in the absorbing state, including any parasitics arising from the packaging and the antenna-IC connection. The proposed method can be extended to measure the IC's input impedance in the modulating state as well.

Long range metal mountable tag antenna for passive UHF RFID systems

Abstract: Development of a long range platform tolerant metal mountable patch-type tag antenna for passive ultra high frequency (UHF) radio frequency identification (RFID) systems is discussed. Results from full-wave electromagnetic simulations are presented to explain the design procedure and to evaluate the performance of the prototype tag antenna. The design uncertainty is quantified based on the expected maximum variations in the tag antenna and tag chip impedance. Wireless RFID measurements based on the EPC Generation 2 protocol are used in experimental tag design verification. The prototype tag achieves 25-meter maximum theoretical line of sight read range on metallic objects at 915 MHz.

Development of a low profile conformal UHF RFID tag antenna for identification of water bottles

Abstract: Development of a low profile conformal RFID tag antenna with an omnidirectional pattern when mounted on a water bottle is discussed. Results from full-wave electromagnetic simulations are presented to explain the design procedure and to evaluate the performance of the prototype tag antenna. The design uncertainty is quantified based on the expected maximum variations in the tag antenna and tag chip impedances. Wireless measurements based on the EPC Generation 2 protocol are used in experimental tag design verification. The prototype tag achieves more than two-meter maximum line of sight read range for 866.6 MHz to 954.2 MHz frequency band.

Performance of inkjet-printed narrow-line passive UHF RFID tags on different objects

Abstract: Inkjet-printing offers a potential alternative to conventional tags manufactured by etching. The inkjet-printed narrow-line tags discussed in this paper are fabricated using less conductive materials than conventional tags. This paper presents the performance of the narrow-line tags when used on different materials. We present read range comparison of passive ultra high frequency (UHF) inkjet-printed narrow-line radio frequency identification (RFID) tags in air and attached to diverse objects. We have also compared the results to a dipole-type commercial copper fabricated tag. Measurement results show that materials under identification affect narrow-line tag performance such as read range and operational frequency and bandwidth.

Performance of Single and Double T-matched Short Dipole Tag Antennas for UHF RFID Systems

Abstract: ─ The impact of tag antenna and chip impedance tolerances on power transfer between these components is investigated analytically. Means for efficient computation of the minimum and maximum power transmission coefficient under given impedance tolerances are developed. The presented sensitivity analysis is employed to quantify the design uncertainty of single and double T-matched short dipole tag antennas for UHF RFID systems. The simulated and measured performance of the two tag antennas is analyzed

Effects of laboratory-scale IC attachment methods on passive UHF RFID tag performance

Abstract: This paper presents laboratory-scale methods for attaching integrated circuits (ICs) to passive ultra high frequency (UHF) radio frequency identification (RFID) antennas and discusses the effects of the attaching methods on tag performance. Commercial passive UHF RFID ICs were used. The studied attachment methods were strap attachment and direct IC attachment. One antenna design was developed for strap attachment where the IC was attached together with a strap, and two different antenna designs were developed for direct chip attachment. In addition, etched copper loop arm antennas for strap attachment and inkjet-printed loop arm antennas for direct chip attachment were studied. The measurement results show that the interconnection between the IC and the antenna is of paramount importance and that the performance of the tag is strongly dependent on the quality of the interconnection. The results of this study provide knowledge for reliable IC attachment in prototype laboratory conditions.

Modification of printed wearable strain sensors by PTF ink particle content adjustment

Abstract: Silver ink conductors and passive ultra-high frequency (UHF) radio frequency identification (RFID) tags were printed by the screen printing method on stretchable PVC substrate. Two inks with different particle content were used. We investigated the electrical performance of the conductors in unloaded conditions and during straining with resistance measurement. The printed RFID tags were characterized in similar circumstances through wireless tag measurements. The goal of the study was to evaluate the usability of printed conductors and RFID tags as strain sensors and to find out, if it is possible to modify their strain sensitivity by adjusting the ink particle content. The results showed that the particle content could be used to modify the strain sensors based on printed conductors and RFID tags. Both structures offer various possibilities for applications, such as monitoring of human bodily functions and movements.

Analysis of using high-resistance RFID tag antennas for robust impedance matching

Abstract: An analytical framework for evaluation of platform-tolerance of RFID tags is developed and the potential platform-tolerance achieved with high-resistance tag antennas is demonstrated. A method for transforming the predominantly capacitive and low-resistance tag chip impedance for matching with this type of antennas is also proposed.