Radio-frequency identification (RFID) is becoming important with emerging applications for smart cities. RFID Tags are required to be small in size, low in cost and must exhibit as long read range as possible. There is a direct tradeoff between Tag antenna size and its read range. In this work, we study this tradeoff through the use of a relatively higher dielectric constant substrate, volumetric folding, and slow-wave structures (SWS). A 3D antenna design is chosen due to two reasons, 1) it can be folded on a 3D structure, 2), the 3D structure can be used as a package for electronics (in case of active RFID implementation). To enable a low-cost realization, the antenna substrate (package) has been 3D printed with filaments of . A dipole antenna has been folded on this 3D substrate, in a way that the electromagnetic fields radiating from various segments of the antenna do not cancel with each other. Finally, the antenna is loaded with specially designed SWS, whose values have been estimated using artificial transmission line theory. The final antenna design, operating at 866.9 MHz, has a of 0.26 and demonstrates a radiation efficiency of 32%. The antenna is integrated with a commercial RFID chip (Monza R6) through a silver paste and the measured read range is 2.73 m, while the corrected read range is 4.05 m when the impedance mismatch is considered. Despite being one of the smallest and the lowest cost design (involving 3D printing), the Tag demonstrates one of the highest read range.
Smart connected things that can sense, interact, and share data have a huge potential in enabling a smart environment. Due to the rising interest in realizing the internet of things to provide smart services in smart cities, there is a requirement of vast deployment; therefore, things/tags need to be low in cost and compact in size. Radio Frequency Identification (RFID) is one of the technologies that can enable sensing and wireless communication between things. In this paper, additive manufacturing is used to minimize the cost of RFID tags while slow-wave structures (SWS) are explored to make them compact. The largest element of RFID tags i.e. antenna is initially taken as a standard half-wave dipole then folded to employ SWS along the parallel conductors. The process of folding and SWS loading have been carefully performed to ensure decent radiation efficiency and read range. To fabricate the proposed RFID tag, silver nanowires-based conductive ink is employed while the substrate is 3D printed. The overall tag size is 54 x 56 x 0.5 mm 3 (ka=0.71), and it has a read range of 6.4 m at 867 MHz.
As the Internet of Things (IoT) and sensing technologies are spreading out, modern systems require wireless and real-time data transfer between devices. RFID technology is one of the most used technologies for this information exchange. For compact devices, antenna in package (AiP) concept presents an advantage in this scenario because the antenna does not need any additional space while the package protects the electronic components and sensors from the environment. In this paper, an AiP is designed and miniaturized by employing volumetric folding and dielectric loading techniques. Firstly, a dipole in free space is analyzed by folding it into a cuboid shape. Later, a free space is replaced with the dielectric as AiP body material to achieve the required miniaturization for the RFID band. The proposed AiP resonates at 891 MHz with a đť’Śđť’‚ of 0.27 and exhibits a decent efficiency of 34%.
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