Hardware Design and Deployment Issues in UHF RFID Systems

Recently, radio frequency identification (RFID) have created emerging applications for tracking, sensing, and identifying various targets in wide-ranging areas such as supply chain, transportation, airline baggage handling, medical and biological industry, and homeland security. RFID systems with a variety of radio frequencies and techniques have been introduced. Among them, ultra-high frequency (UHF) band passive RFID systems that operate in the 860 – 960MHz band have drawn a great deal of attention because of its numerous benefits, such as cost, size, and increased interrogation range. In particular, the interrogation range of the UHF RFID system is comparatively large, due to the use of a travelling electromagnetic (EM) wave to transfer power and data. The increased interrogation range makes it possible for UHF RFID systems to revolutionize commercial processes, such as supply chain management. Several major supply chain companies such as Wal-Mart and Tesco plan to mandate the use of an UHF RFID system in their supply chains (Finkenzeller, 2003). UHF band passive RFID system based on modulated backscatter has a unique characteristic, quite distinct from those encountered in most other radio systems which involve active transceivers on both sides of the link (wireless LAN, Bluetooth, etc). Because tag has no internal power supply, RFID reader must always supply the power in order to communicate with tags. This puts a different emphasis on the radio link, hardware design, and deployment aspects (Nikitin & Rao, 2008). In this chapter, we review recent works in current passive UHF RFID systems to provide guidance regarding RFID system design and deployment. We cover the following topics. • UHF RFID radio links using the link budget concept to calculate forward-link and reverse-link interrogation ranges. • Hardware design considerations at the reader: phase diversity and quadrature signal combining, phase noise with range correlation effect, and transmitter leakage reduction methods. • Deployment issues including reader-to-reader interference The organization of this chapter is as follows. Section 2 analyzes the RFID link characteristics and shows the necessity of link budget concepts to calculate the RFID interrogation range. The hardware issues in an RFID reader are discussed in Section 3 along with recently published research results. Section 4 shows the RFID deployment issues with