| Abstract [eng] |
This master’s thesis examines methods for the fabrication of passive near‑field radio tags operating in the gigahertz range, with a particular focus on the design of chipless RFID tags on an FR‑4 substrate. The aim of the work is to analyze the spectral signatures of various tag geometries and to assess how changes in geometry affect those signatures. The introductory review covers the state of the art in the literature, revealing that chipless RFID tags offer an alternative to barcodes for tracking items when only a small amount of information (a few bits) is required and a direct line of sight is unavailable. It also surveys possible tag fabrication techniques, reading methods, and electrical characteristics, from which three designs were selected for further study: U‑shaped, ring‑shaped, and split‑ring geometries, all implemented on 1.6 mm‑thick FR‑4 substrate. In the methodological section, three geometric variants of each chosen design were modeled in CST Studio Suite to simulate their S‑parameters over the 1 GHz to 10 GHz frequency range and thereby determine their spectral signatures. In the next phase, prototypes were fabricated on FR‑4 and their S‑parameters were measured experimentally from 1 GHz to 6 GHz using a LiteVNA 64 vector network analyzer, confirming that ring‑shaped tags afford the greatest spectral distinguishability. After refining the resonant frequencies of the selected tags, the ring design yielded the best performance when its resonances were clustered in the 3 GHz to 5 GHz band. Finally, a ±10 % variation in the dielectric constant of the FR‑4 substrate was modeled, showing a corresponding resonant‑frequency shift of up to 180 MHz. |
