ABSTRACT
This chapter explores the design and performance considerations for antennas in transponders. It presents a basic review of antenna theory with special emphasis on the differences used for systems in the low-frequency (LF) and high-frequency (HF) ranges compared to the antennas used for ultra-high-frequency systems. Antenna tuning for Radiofrequency identification (RFID) transponders operating at LF or HF frequencies attempts to make the antenna resonant at the frequency of transmission, thus maximizing the current or the voltage in the system. The chapter describes the types of antennas found in commercial transponders. It considers the requirements for antenna tuning and antenna matching. The chapter also describes the different methods for attaching the antenna to the chip on the transponder. In an RFID transponder, the load of the antenna is the integrated circuit that will be powered by the energy supplied by the antenna.
