RFID systems are composed of three major components, namely, readers, transponders and antennas. A majority of the transponders are passive or batteryless, and are powered by the energy transmitted by the reader antenna, although active transponders are finding limited applications in some high-end applications, where security, reliability, and automatic operation capability are of the utmost importance, and can thus justify the use of more costly tags than the passive ones. The design of RFID systems is very challenging indeed because of demanding specifications coupled with restrictions on the available size cost, and platform tolerance of tags that may be mounted on a diverse array of products. To meet these challenges, it is necessary to combine the expertise on signal processing, antenna technology and system design. This review talk will identify the challenges and describe some of the proposed solutions for addressing them.