Effective Design of Microstrip-Line Chipless RFID Tags Based on Filter Theory

This paper presents an effective design method of chipless RFID tags. With $n$ -bit first- and second-order chipless tags’ equivalent circuits proposed based on filter theory, the relationship between bits and frequency bands of tags is characterized by formulas. Combining with microstrip-line theory, the first-order chipless tag with single quarter-wave open-circuited (O.C.) shunt stub units, and second-order chipless tag with parallel pairs of quarter-wave O.C. shunt stubs are designed, respectively. The pros and cons for each type of the chipless tag are discussed. Two types of 5-bit chipless tag examples are given with good consistent simulated and measured results. In addition, for the second-order chipless tag, we propose a miniaturization scheme, enhancing the antidamage ability simultaneously. Damage test shows that the second-order chipless tag has the good antidamage ability, especially for the miniaturized tag. Finally, the bit extension by the formulaic method is discussed, emphasizing a promising practicability.