From an historical perspective it is the small CMOS integrated circuits (versus inductively coupled transponders) which incorporated microwave Schottky diodes that made it possible to manufacture small passive RFID tags. In this chapter it is demonstrated how recent improvements in CMOS technology (0.18u and later) make it possible to use an inexpensive MOS transistor for the EPC GenII/ISO 18000-6c compliant transponders that operate in the UHF band. The basic variables for designing low-power (high-readability) RFID tags and details of incorporating temperature sensors into semiconductor chip designs at the Auto-ID Labs, Fudan University, Shanghai are described.

This chapter explores chip design principles that affect the performance of RFID tags. The metrics of tag performance will be illustrated and the corresponding optimization technologies will be introduced. Many early implementation issues for RFID tags involved low read rates such that tags did not “wake up” in response to interrogator signals and transmit their IDs, especially with transponders operating at UHF frequencies that are subject to interference from liquids and metals.

Metrics of tag performance

In RFID applications, tag performance will directly influence the success of the whole system. Understanding the metrics of tag performance is important in order to foresee the overall system performance. This section will analyze the metrics of tag performance, including read range, read rate, communication speed, etc.