32 nd URSI GASS, Montreal, 19-26 August 2017 Development of Passive UHF RFID Tag on Flexible Foil for Sport Balls Pressure Monitoring Ahmed Rennane (1),(2),(3) , Abanob Abdelnour (2) , Darine Kaddour (2) , Rachida Touhami (1) and Smail Tedjini (2) (1) Université des Sciences et de la Technologie Houari Boumediene (USTHB), Algeria (2) Université Grenoble Alpes/LCIS, 50 rue Barthélémy de Laffemas -BP 54 26902 Valence Cedex 9 –France (3) Centre de Développement des Energies Renouvelables, CDER, 16340, Algiers,Algeria Abstract In this paper, an integrated solution based on passive UHF RFID tag sensor is proposed to measure the pressure on different types of sports balls. A comparison of two commercial piezzoresistive sensors based on different technologies is performed for this type of pressure measurement application. Several external sensor interface chip configurations (SFE) have been tested and adapted to the resistance variation range that presents each type of sensor. In both function modes: passive or semi-passive, a smart RFID tag concept is fully validated through measurements on different types of sport balls and the results are compared with data from Electronic Ball Pressure Gauge CJ-01 model. 1. Introduction The design of passive UHF RFID tags with additional functionalities is still an attractive topic in the literature. One of the technologies that greatly enabled the large development of these systems is printed electronics on flexible substrate that makes possible to produce low-cost systems in large-scale production [1]. There are two main methods to include the sensing capability in the UHF RFID tags. The first method using the tag’s antenna as a transducer. Research based on this simple but challenging method exploits the analog response of the backscatter signal of the sensing RFID tag without using any additional RF circuitry [2,3]. In the other method, two configurations are possible. Indeed the sensed data is collected separately by a distinct sensor and relayed via the RFID tag to the reader [3]: a) single-chip architecture without microcontroller unit have been reported by [4,5]; b) microcontroller architectures in combination with RFID chips and different types of sensors as reported in [1],[6]. On the other hand, the correct pressure measurement check on sport balls like football, volleyball and basketball is essential to ensure fairness in sports and plays a big part in providing a level playing field for all athletes in Olympics. Nowadays, the pressure of the air inside a sport balls is measured by a pressure gauge, and the pressure gauges are checked against pressure balances. It assumed that long storage of sport balls affect its pressure. Therefore, a control of this parameter will be indispensable. In this work, we present the design and the characterization of an RFID tag with integrated pressure sensing capabilities. The designed tag uses the SL900A RFID chip [7] and includes a commercial FSR force sensor with an adaptation resistor to the sensor interface of the chip. In this sense, the pressure applied in the ball can be measured directly by a wireless UHF RFID reader. 2. A comparison of two commercial piezzoresistive sensors In this section, we have experimentally evaluated in terms of repeatability, sensitivity and linearity, in the pressure variation range that suits our application, two major commercial force sensitive resistors: the Interlink FSR sensor and the Flexiforce sensor through a series of measurements. Therefore, we have introduced the sensor between the two bodies of the ball. In this measurement conditions, the maximum errors obtained in terms of repeatability error characteristics of each tested sensor were 3.36% for FlexiForce A201-25, 1.77% for FSR 400 and 5.24% for FSR402. Based on this test for sensor performance comparison, the Flexiforce and FSR400 have been chosen to be integrated with the external sensor interface (SFE) of the SL900A device to develop an UHF RFID tag with sensing capabilities for the measurement of ball pressure. To this end, three configurations have been tested for the selected sensors using equation (1) for EXT2 input and equation (2) for EXT1 input.  ܥܦܣ ா௑ଶ = 0.135 ∗ (1 +  ௙  ி௟௘௫௜ி௢௥௖௘ ) (1).  ܥܦܣ ா௑ଵ = ி௟௘௫௜ி௢௥௖௘ ܫ∗ ௌா௉ (2). Figure 1. Technique used to adapt the output sensor to the EXT2 analog input.