Methodology for Design of High Code Density and Robust RFID Tags

This letter presents a new methodology for designing chipless radio frequency identification (RFID) tags with high code density and robustness and validates its effectiveness. The method includes four main steps: designing a resonant unit without a second harmonic, constructing the entire tag structure using a nested loop strategy, adjusting the distribution of resonance points to achieve uniform spacing, and further optimizing the tag performance. Using this method, we designed a chipless tag with a code density of up to 180.45 bits/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula><inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ _{0}$</tex-math></inline-formula><inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> and a working frequency range of 7.9 GHz to 13.6 GHz. Experimental results demonstrate that the designed tag has a coefficient of variation of the resonance frequency point interval of 12.97% and a small variation in the resonance peak amplitude of 4.36 dB. These results confirm the effectiveness of the proposed method in achieving high code density and robustness in chipless RFID tags.