This thesis analyzes impedance matching concepts in passive radio frequency identification (RFID) system, which is including a reader and a tag. The tag is consist of an integrated circuit chip and an antenna, both with complex impedances. For maximum power translation, the chip and the antenna must be conjugate matching in input impedances.

This thesis proposes an antenna, which not only the real part but also the imaginary part of the input impedance can both be tuned. Also, the antenna can meet other RFID antenna requirements, such as the compact size and the omnidirectional pattern.

For measuring the characteristics of the antenna, we propose another antenna, which can be directly measured and is analogous to the original one, and compares
differences with the original one. Their differences are small, so it can be certain that the original design is suitable for RFID applications.