Elizabeth Colin

Shunt Resistance Variation for a Constant Power Supply in UHF RFID Tags

In the case of short reader-to-tag distances, shunt resistance diverts current in order to protect the chip but this affects the chip power supply and the Delta Radar Cross Section. This paper presents a shunt resistance law variation which keeps a constant power supply in the RFID chip and the impact of this law on the Delta Radar Cross Section.

Improving indoor localization within corridors by UHF active tags placement analysis

When deploying emitting beacons, here UHF active RFID Tags, a critical issue is where the emitters should be placed, yet too few studies on this topic have been carried out. This paper focuses on the placement of the tags in order to improve the accuracy in the position estimation. This work presents a statistical study of tags positions and gives correlation between their positioning and the localization system accuracy. Guidelines are given for the tags placement in order to increase accuracy in the context of trilateration based location architecture within a hallway.

Shunt Behavior in RFID UHF Tag According to ISO Standards and Manufacturer Requirements

This paper deals with ultra-high-frequency (UHF) radio-frequency identification (RFID) tag modeling. Examples of electrical models and measurements of backscattering by load modulation in RFID systems can be found in scientific literature in far-field conditions. Load modulation and loading effect are based on the same physical phenomenon: the antenna current is modified by switching the load impedance between two impedances which are frequency dependent. All these models neglect the shunt resistance which can deeply affect the load impedance and may produce failures in the communication system.

Delta RCS of UHF RFID taking into account the shunt resistance in the tag model

This paper deals with UHF RFID tag modeling. Recent electrical models present theory and measurements of backscattering by load modulation in RFID systems. These models fit with measurements in far field conditions. Load modulation and loading effect are based on the same physical phenomenon: the antenna current is modified by the load impedance. In far field, we can assume that the load modulation is made by switching between two impedances which are frequency dependent. These models neglect the shunt resistance which can deeply affect the load impedance and may produce failures in the communication system.

Impact of ferromagnetic obstacles on LF-RFID based indoor positioning systems

Low-Frequency (LF) Magneto-Inductive (MI) communication, used in LF Radio-Frequency Identification (RFID) systems, is very well suited for indoor positioning applications since LF magnetic fields are not greatly affected by the environment. However, LF magnetic fields may be distorted by ferromagnetic objects or get affected by LF Electromagnetic Interferences (EMI), which affects the accuracy and reliability of LF-RFID based positioning systems. In this paper, we consider an indoor positioning technique based on the LF (125 kHz) MI communication and study the challenges faced by this technique because of ferromagnetic objects. We analyze the results based on experiments and simulations.

Indoor performance analysis of LF-RFID based positioning system: Comparison with UHF-RFID and UWB

Existing localization technologies face several challenges indoors because of their sensitivity to the environment. In this paper, we present an indoor localization system based on Low Frequency (LF) Radio-Frequency Identification (RFID) as a reliable and low-cost solution, which is less affected by challenging indoor conditions. The presented system makes use of LF (125 kHz) magnetic fields for reliable localization in multipath and Non-Line-of-Sight (NLOS) environments. The objective of this paper is to analyze two-dimensional (2D) positioning estimation performance of LF-RFID based localization system in comparison with the localization systems based on Ultra-High-Frequency (UHF) and Ultra-Wideband (UWB) technologies. We present results for 2D localization tests for these three systems in a challenging indoor environment of area 315 square meters. The presented system, which is implemented using off-the-shelf components, achieves a mean positioning error of 1.53 m with a standard deviation of 0.91 m for 352 position estimations while keeping the positioning error below 2.82 m for 90% of the cases.

Location performance law according to the dimensions of the corridor using trilateration

Beacon positioning is a challenging issue in indoor positioning systems, as it considerably affects their performance. The positioning mean error may vary from 85 cm to 7 m depending on the beacons placement. This paper presents a semi-empirical law to predict location performances (accuracy and precision) in a corridor environment for given dimensions. This law can be applied to narrow indoor environments. This work is carried out in a corridor environment at two different frequency bands i.e. 433 MHz and 868 MHz with active UHF-RFID tags. Trilateration techniques are applied on Received Signal Strength Indicator (RSSI) values acquired from the tags. In this paper we study the impact of tag placement on the performance of location estimation in conjunction with a theoretical channel model. We choose the positions with best tag performances in the environment and compare the results for two frequency bands to define a law for location performance prediction depending on the dimensions of the corridor. This law helps to design a localization solution by providing two things: the density of the tags to be deployed and the positioning of the tags as a function of corridor dimensions for given frequency band and for the expected performances. We are able to achieve sub-meter accuracy (mean error) and precision (standard deviation) for both frequency bands.