Thèse Implémentation de Tags Rfid Uhf Basé sur le Concept d'Antenne Multi-Ports H/F - Doctorat.Gouv.Fr

Établissement : Université Grenoble Alpes École doctorale : EEATS - Electronique, Electrotechnique, Automatique, Traitement du Signal Laboratoire de recherche : Laboratoire de conception et d'intégration des systèmes Direction de la thèse : Nicolas BARBOT ORCID 0000000163559109 Début de la thèse : 2026-10-01 Date limite de candidature : 2026-07-31T23:59:59 The objective of this PhD thesis is to design a new generation of UHF RFID tags which can outperform all classical UHF RFID tags designed in the last 20 years. For this, the architecture of a tag has to be modified but without increasing the power needed to activate the tag and without increasing its cost. Finally, the tag has to be compliant with the EPC Gen2 protocol which means that the proposed tag has to be read with classical RFID readers already deployed. To achieve these objectives, this PhD subject relies on the concept of multi-port antenna. During the PhD, the candidate will design the first multi-port UHF RFID tag. The proposed multi-port tag should be able to improve simultaneously the harvested power and the modulated backscattered power. If successful the read range of the proposed concept should be increased by 41% compared to classical (single-port) UHF RFID tags. The RFID technology is the major tool to identify items remotely. For this, an RFID tag is attached to each item and can be read by a distant reader. The tag is composed of an antenna and a chip (digital circuit) and can be entirely passive i.e., it does not require the presence of a battery. The actual RFID systems are able to identify several hundreds of tags per second at distances which can be higher than 10 meters. Finally, due to its simple and passive architecture, the cost of a tag has been reduced to a few dozen cents.
In the past, the read range of a RFID systems were limited by the harvested power needed to activate the tag, thus most of the research effort was oriented to reduce the tag sensitivity and improve the matching between the tag and its antenna. Over the last 20 years, tag sensitivity has been improved by 1 dB per year on average. This small improvement limits the adoption of the technology. Today, sensitive chips can be activated with a power as low as -23 dBm. As a result, performance of a RFID system can now be limited by the tag sensitivity but also by the reader sensitivity [1]. Thus, we are currently at a turning point where the performance of an RFID system can not be improved by the tag design only, but by a joint approach which combines the characteristics of the reader and the tag.
Finally, in 2023, more than 45 billion of UHF RFID tags have been sold. Increasing the performance
of this technology at the physical layer represents a significant reduction in terms of time and cost during the deployment and use of any RFID system and open the way to new applications. The objective of the PhD subject is to significantly improve the performance of the UHF RFID technology by using the concept of multi-port antennas. The proposed multi-port tag should be able to improve simultaneously the harvested power and the modulated backscattered power. If successful the read range of the proposed concept should be increased by 41% compared to classical (single-port) UHF RFID tags. Classical tags use a single port between the antenna and the chip. This constitutes a simple architecture but also limits the performance of the technology since the harvested power is entirely bounded by the Friis equation. The maximum read range at which a tag can be activated by a reader is called the forward read range and strongly depends on the matching between the RFID tag chip and the RFID tag antenna.
On the other side, the round-trip read range correspond to the maximum read range at which the tag can be detected by the reader. This round-trip read range is function of the modulated power backscattered by the tag towards the reader and is proportional to the delta RCS of the tag.
More importantly, the real real read range of a UHF tag simply represents the minimum between
these two read ranges (forward and round-trip read range).From these simple constraints, we can clearly see that improving the tag sensitivity is not the optimal choice since the performance can also be limited by the round-trip read range, which makes the approach non-optimal. Instead, both tag matching and delta RCS have to be improved jointly.
However, these two quantities are bounded for classical tag composed of a single port. For example, for a classical half-wavelength dipole at 915 MHz has the minimum value for the power wave reflection coefficient is 0 and the maximal delta RCS for passive tags is equal to -22.4 dBsm (57.5 cm²) These two values are actually a bound of the current RFID technology and limits the performance of all tags on the market. In order achieved a significant improvement in term of read range, both matching and delta RCS values have to be optimized simultaneously. This PhD proposal propose the concept of multi-port tags to significantly improve the performance of the RFID technology. Contrary to classical tags, these tags present multiple ports. Each port is connected to a (different) antenna. These multi-ports tags allow ones to break the simultaneously the bounds in term of received power and backscattered power and hence maximize the overall read range.
However, these multi-port tags are, for the moment, a theoretical concept and do not exist yet (see the conclusion of [2]). To become a reality, both multi-port chips and multi-port antenna have to be discovered.

A master degree (or equivalent) is required to start the PhD. A good level in english is also expected.

Solid skills in:
-RF, antenna design, signal processing...
-Electromagnetic simulation (HFSS, CST, NEC2...)
-RF measurements (VNA, spectum analyzer, real-time spectrum analyzer).