On the Use of Pre-Equalization to Enhance the Passive UHF RFID Communication under Multipath Channel Fading Dr. Taoufik Ben-Jabeur & Dr. Abdullah Kadri Qatar Mobility Innovations Center (QMIC), Qatar Science and Technology Park, Doha, Qatar taoufikb,[email protected] Background: We consider a monostatic passive UHF RFID system where it is composed from one RFID reader with one antenna, for transmission and reception, and RF tags. The energy of the continuous signals transmitted by the RFID reader is used to power up the internal circuitry of the RF tags and to backscatter their information to the reader. In the passive UHF RFID, we note the absence of source of the energy other than that is coming from the continuous wave. Experiences show that the presence of the multipath channel fading can reduce dramatically the received power at the tag. Therefore, the received energy isn't sufficient to power up the RF tag. To remedy this problem, we propose a pre-equalizer applied on the transmitted reader in order to maintain a useful received power able to power-up the tag. Objectives: This work aims to design a specific a pre-equalizer for passive UHF RFID systems able to combat the effect of the multipath channel fading and then maintain a high received power on the tag. Methods: a.First stage, we assume the knowledge of the multipath channel fading and the continuous wave. Then, the pre-equalizer is designed for a fixed Rayleigh multipath channel in order to maximize the energy of the receiver signal on the tag. b.Proprieties are extracted from the designed pre-equalizer associated to the fixed channel. c.More general equalizer uses these proprieties to design an equalizer that can be applied for any unknown multipath Rayleigh channel. Simulation results: Simulation results are provided to show that the proposed pre-equalizers allow combating the effect of the multipath channel fading and thus increasing the received power at the RF tag. The energy consumption of the tag is still the same and all operations are made at the RFID reader side.


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