Flexible Meandered UHF RFID Tag Antenna on a Paper-Backed Substrate: Impact of Chip Placement and Material Proximity for Industrial Applications

In this work, the design and experimental validation of passive UHF RFID tag antennas are presented with the objective of evaluating the impact of chip placement and miniaturization approaches on tag performance. Four initial antenna layouts were developed by varying the position of the RFID integrated circuit within a coupling loop. The results show that chip placement directly affects the coupling-loop efficiency, the antenna–chip matching condition, and the practical tolerance of the structure to fabrication-related variations. Simulations and measurements identified Antenna 1 as the best-performing reference configuration, exhibiting the most favorable impedance behavior around 866 MHz and a measured power sensitivity of −16.3 dBm. Based on this reference design, a miniaturized version (Antenna 5) was obtained by integrating meander lines and capacitive end-loading, reducing the physical size while maintaining resonance at 866 MHz. Both structures were fabricated and evaluated using a Voyantic Tagformance measurement system, with read-range measurements performed under free-space conditions and in proximity to dielectric and conductive materials. The results demonstrate a maximum read range of 8.6 m for Antenna 1 in free space, while Antenna 5 preserved a read range of 6.3 m. In the presence of copper, Antenna 1 maintained a read range of 3 m, whereas Antenna 5 achieved approximately 0.5 m, highlighting the trade-off between miniaturization and robustness under conductive loading.