Edinburgh Napier University

  This paper presents a new analog design of a radio-frequency identification (RFID) tag antenna with a long-read range oriented to localization applications. The actual work focuses on the analog input characterization of antenna impedance by studying the capacitive effect, created by the gaps, and the effect of introduced opened circuited L-shaped stubs, on the RFID tag characteristics. Numerical and measured results confirm that proposed tag antenna performances are significantly improved by introducing gaps and stub structures and after optimizing their dimensions such as length and width. Introduced stubs with optimal dimensions lead to a well level of impedance matching, lower return loss values. Furthermore, two operating frequency bands have been created when the antenna is excited by a 50 Ω port: a low-frequency band around 837 MHz and a higher one around 927 MHz These results have been validated by measured ones. The proposed RFID antenna is mainly composed by three split rectangular resonators (SRR) where introduced structures concern only the larger SRR. The optimized antenna has an area of 76 × 24.6 mm2 and is printed on the Taconic RF-60A substrate with a dielectric constant of 6.12, the thickness of 1.6 mm, and a loss tangent of 0.025. Simulation results show interesting communication performances, of the proposed tag antenna, with a return loss of -22.3 dB around 916 MHz and a long read range up to 25m when it is fed by an industrial Mping M730 chip having a power sensitivity of -24dB and an output impedance Zchip16-j194 (Ω) at 916 MHz.