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Analysis and synthesis of wideband scattered signals from finite-size targets – aspect-independent RF analog footprint

Periodic Reporting for period 1 - SCATTERERID (Analysis and synthesis of wideband scattered signals from finite-size targets – aspect-independent RF analog footprint)

Reporting period: 2018-09-01 to 2020-02-29

"The need for information identification and capture is a matter of prime importance in modern societies. Every sectors of society rely on the identification of data exchanged, the updating of the data recorded on a tag and the measurement of physical parameters. Key issues such as the way to reduce power consumption, to improve the communication quality-of-service and to enhance connectivity have recently come up for lots of industries. One important direction for researchers to consider is to develop battery-less, low cost tags for wireless identification and sensing. Lots of improvements have been done in the past few years on communication systems, based on electronic devices where an integrated circuit is at the heart of the whole system. The democratization of these chipped based systems like the radiofrequency identification (RFID) one will give rise to environmental issues in the future. However, these improvements pave the way for the development of new concepts based on radar or reflectometry principles. The main goal of this project is to develop a new generation of systems based on chipless radiofrequency (RF) labels, operating like radar targets, and compatible with new functionalities. ScattererID project aims at introducing the paradigm of RF communication system based on chipless label, that is to say tags without any chip, bringing an ID, able to communicate with radio waves, having extremely low costs and where other useful functionalities can be added. With comparable costs to a barcode, these labels should stand out by providing more functionalities than the optical approach. Thus, this research project aims to carry on Etienne Perret’s work begun on chipless at the LCIS laboratory with the objective to show that it is possible to associate the chipless label ID with other features like the ability to: 1) write and rewrite the information (ID), and 2) associate an ID with a sensor function, 3) associate an ID with gesture recognition. These advances are primarily based on important technological breakthroughs. From a theoretical point of view, to our knowledge, too few works have focused on the accurate understanding of the physical phenomena involved in both cases, particularly those linked with the phenomena that occurred at the Nano scale (1- Nano switches | 2- sensors based on nanowires) and the modification of the RF waves characteristics that interact at the macroscopic scale and contain the useful information. For instance, the possibility of designing reconfigurable and low cost (i.e. printable) tags involves the development of original approaches at the forefront of progress, like the use of CBRAM from microelectronics, allowing to achieve reconfigurable elements based on Nano-switches. From a practical point of view, the ultimate goal is to demonstrate that the chipless RFID has the greatest assets to compete the barcode and succeed in leadership positions in some practical applications. The development of a new easy to use and low cost technology, is eagerly awaited, that would allow the ""objects"" to communicate for traceability means. This project is very promising for Europe: the need for a new market for printer companies and the pulp and paper industry is already shown by the quick development of inkjet printing of conductive materials. Tomorrow, most people will have bought conductive ink cartridges, already compatible with their own inkjet printer to print conductive patterns on sheets of paper. In that context “smart packaging” is a significant target for these companies and everything has to be done."
Significant work has been done on “RF Switches” (WP1), “Robust tags” (WP2) and “Gesture Recognition” (WP3) workpackages during reporting period n°1.

For instance, totally imprinted CBRAM RF switches have been achieved using transfer printing techniques. One of the most relevant results about this topic is that we are now able to control the resistance of these switches by controlling the tension / current applied to the CBRAM cell. We also have observed some nonlinear behaviors, and we are now trying to exploit these phenomena that could be very interesting for the communicating part of the project. Regarding WP2, we have introduced a totally planar resonant scatterer with roll invariant cross polarization. This work has been first driven from a theoretical point of view, and then an original implementation has been proposed. The characterization of this device shows good agreement with the theory and the simulations. About WP3, a Chipless RFID label with identification and touch sensing capabilities has been introduced.

A test bench has been built and automated to perform chipless tag characterization. With this dedicated bench designed and based on the Starlab platform, it is now possible to measure the RCS of objects in 3D.

In addition, members of the ScattererID project participated in several national and international conferences. A significant number of papers (more than 10) have been submitted to international scientific journals. Two workshops with 3 invited guests have also been organized.
The following results can be considered as notable progress beyond the state of the art. Papers describing these results are currently being written. Most of them have already been submitted to international journals. These results relate to CBRAM cells for RF applications, and robust chipless tag for identification or sensing applications:

- A novel methodology for achieving a variable resistance for CBRAM cells for microwave applications has been introduced.
- Electronically rewritable chipless RFID tags have been designed, fabricated through thermal transfer printing on flexible PET substrates and characterized.
- A smart and robust chipless RFID label with identification and touch sensing capabilities is being developed. First results are encouraging.
- About sensing, for the first time we have shown that contactless characterization of thermal expansion coefficient (CTE) of metals can be realized based on free-space RF measurements. This concept is now used to convert chipless tags to temperature sensors.
- Last but not least, we have introduced the first planar resonant scatterer with roll invariant cross polarization. Based on the introduced theory related to this concept, new ideas have emerged, and we continue to work on the implementation of some of them.

Expected results until the end of the project are still the ones described in the Annex 1 to the Grant Agreement (Description of the Action).
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