Performance evaluation of a passive UHF RFID tag antenna using the embedded T-Match structure

The impedance matching between an RFID IC (Radio Frequency IDentification-Integrated Circuit) and an RFID tag antenna is of a critical importance in RFID tag design. A poor match impedance results in less power delivered to the RFID IC and poor antenna performance that lead to poor communication between the reader and the tag. In this work, we search to match the input impedance of the planar dipole antenna for the UHF RFID (Ultra High Frequency) applications to a RFID chip at 915 MHz. To achieve this goal we have adopted the most popular method of adaptation “T-Match” which enables proper matching between the tag and the chip for maximum power transfer. HFSS (High Frequency Structure Simulator) tool was used as a platform to design, to match, to optimize and to present the circuit and the radiation parameters of the antenna printed on a flexible substrate. The results obtained by HFSS were compared to those obtained by CST MWS (Computer Simulation Technology-MicroWaves Studio). The match between the chip and the antenna is computed in terms of the power transmission coefficient.