Gianfranco Andia Vera

Analysis of Harmonics in UHF RFID Signals

In this paper, a detailed study is proposed on the properties of UHF RF identification (RFID) signals when the communication between the reader and tag is established. The main objective is to analyze the harmonics produced by the chip and radiated by the tag antenna. From experimentation, the characteristics of the nonlinearities contained in the signals are highlighted and linked to the theory of the backscattering in the RFID context. Several experiences taking into account the standards are proposed. Moreover, several commercial tags are considered in order to compare the observations. The used configuration, the experimental setup, and the protocols are described in detail. In particular, the generation of periodic and reproducible sequences of bits is introduced and its advantages are emphasized. Finally, contrarily to the classic approaches that tend to eliminate the harmonics generated by the rectifiers of tags, the great interest of the possible exploitation of backscattered harmonics is discussed in perspectives and some ideas of applications are given.

RFID Test Platform: Nonlinear Characterization

This paper presents a complete radio frequency identification (RFID) test platform to characterize the nonlinear effects produced by passive ultra-high frequency (UHF) RFID chips. In full operation mode, automated measurements of activation power, harmonic response level, and impedances are performed in a wide frequency range up to the fourth harmonic. The characterization method, platform composition, and operation are explained through real measurements on UHF Class-1 Generation-2 chips. A harmonic treatment is presented thanks to the joint use of an RFID tester and impedance tuners, and the effect of the antenna-chip impedance matching on the harmonic responses is compared before and after treatment. To the best of our knowledge, no similar platform has been presented in the literature.

Harmonic Power Harvesting System for Passive RFID Sensor Tags

This paper introduces a relevant concept of energy harvesting for passive UHF radio frequency identification (RFID) relying on the exploitation of the power carried by the third harmonic signal generated by the RFID chip. The idea consists on the use of the sole third harmonic energy to power up an associated sensor to the RFID tag. The proposed concept is first demonstrated in simulation thanks to an equivalent model for the RF front-end of a passive UHF RFID chip. Although the proposed model is simplified, it considers the generated nonlinear signals, allowing an efficient design of the rectifier circuit, which is responsible of harvesting the third harmonic power besides ensuring the activation of the RFID chip in order to communicate with the reader. The power driving between the RFID chip, third harmonic harvester, and antenna at the fundamental and third harmonic frequencies is achieved by designing a low-loss distributed three-port impedance matching network. Simulation results confirm the operation of the matching network and the exploitation of the third harmonic signal by analyzing the power at different nodes in the circuit. Measurement results validate the proposed nonlinear chip model. A prototype of the RFID tag harmonic-harvester produces 39 μW of dc power harvested from the harmonic signal, showing good agreement with the simulation results. Finally, a sensor application exploiting the harmonic harvested power to energize a commercial temperature sensor at a distance of 80 cm from the reader is demonstrated.

Redundant backscattering modulation of passive UHF RFID tags

In this paper a study on the nonlinearities effects on passive UHF RFID tags is established. From experimentation, once the communication is established between reader and tag, the evidence of existence of a 3rd harmonic carrying information by the backscattered modulation is presented. Contrary to the classic approaches which tend to eliminate the harmonics generated by the rectifier part of the tag, an idea of their exploitation by defining a redundant channel is discussed.

Tag-to-reader harmonic link in passive UHF RFID

This paper presents a new communication concept for the passive UHF RFID technology, by means of the exploitation of harmonics signals generated by passive UHF RFID chips. The presence of information carried on the harmonics is experimentally shown by conducted measurements on three different EPC Class-1 Gen2 RFID chips. Therefore, and in compliance with the standard requirements, these results are used in the optimal design of a new tag that increases the power level of the harmonic response, while operating also at the fundamental frequency. The performance of this solution is illustrated from simulation and measurement. Results show an improvement of 11 dB on the 3rd harmonic response compared to commercial tags, thereby, enabling new applications, concepts and functionalities for the RFID technology. To the knowledge of the authors, no similar study has been presented in the literature.

Optimum integration of passive UHF RFID tag-rectenna in a single feed dual band antenna

In this paper, a design approach for the efficient integration of passive RFID tag operating at UHF 868 MHz for RFID communication and a rectifier operating at 2.45 GHz for energy harvesting application, both in a single feed dual band antenna is presented. Initially, the RFID chip and the rectifier element were characterized. Therefore, the step by step design process for the integration of each element is carried over, for a maximum power transfer to the passive RFID chip and the rectifying circuitry. The non-linear effects of rectifier and RFID chip are considered in an electric-electromagnetic co-simulation, ensuring the conditions at the threshold activation power at the RFID chip. 36.9 % RF-to-DC conversion efficiency is ensured at 2.45 GHz for -10 dBm input power. The sufficient isolation is provided at both frequencies to support an RFID communication and at the same time, harvesting from the 2.45 GHz band.

Read Range Enhancement by Harmonic Energy Harvesting in Passive UHF RFID

A new approach of integrating the passive UHF Radio Frequency Identification (RFID) technology with electromagnetic energy harvesting function is presented in this letter. The approach is based on using a passive RFID tag operating at 868 MHz for communication purposes whereas a rectifying circuit is designed to harvest its third harmonic i.e., 2.604 GHz generated by the non-linear behavior of the RFID chip. An innovative concept to re-inject the energy harvested into the RFID chip is proposed. Experimental results on the energy feedback operation has shown an RF-to-direct current (dc) conversion efficiency of 33% at -16 dBm input power for the harvesting function and a read range improvement of 2.5 m for the communication function.

Energy paradigms of augmented tags for the Internet of Things deployment

This paper reviews and compares different techniques to collect more energy for passive UHF RFID Tags. The main objective is to allow the tags to embed new functions and provide more than identification. Such additional capture of energy transforms the simple tag into an augmented tag able to perform new functions such as sensing, channel diversity and much more.

Passive RFID-enabled proximity sensor

This paper presents a passive proximity sensor using UHF radio-frequency identification (RFID) technology. The sensing operation allows detecting and counting goods or persons with no RFID tags attached. The system comprises a customized double-antenna sensor tag and a commercial reader. The design is performed at two layers. In the physical layer, a distribution network prioritizes power towards one antenna to detect presence, while allows the other antenna communicating with the reader. In the communication layer, the RFID chip (EM4325) is programmed to set an alarm when triggered by an RF event, and hence changing the tag identifier. Design directives are given and experimental sensing tests consisting of an access gate demonstrates the proposal.

Passive UHF RFID backscattering for indoor lighting control

This paper proposes the use of a passive RFID light sensor in a daylight-adaptive lighting system. In such a system, the dimming levels of light sources are adapted to changing daylight such that a desired illuminance distribution is achieved at the place. The system is composed by photo-sensible passive RFID tags used as light sensor nodes and RFID readers connected to a central controller. The use of the passive UHF RFID technology avoids the use of complex feedback light control algorithms as also simplify the deployment of the sensor network. Experimental results showed the proposed solution. The light variations can be sensed with high resolution having completely passive and wireless sensors.