Radio Frequency Identification: Decades at a Time

In this article, we briefly review the history of the use of radio signals to identify objects, and of the key Radio Frequency Identification (RFID) standards for ultra-high-frequency (UHF) and near-field communications that enabled broad use of these technologies in daily life. We will compare the vision for the future presented by the Auto-ID Lab in the early 21st century with the reality we see today, two decades and a little after. We will review some of the applications in which UHF RFID technology has become hugely successful, others where High Frequency Near-field Communications (HF NFC) is preferred, and applications where optical identification or active wireless communications are dominant. We will then examine some possible future paths for RFID technology. We anticipate that UHF read capability will become widely available for cellphones, making it as universal as NFC and Bluetooth are today. We will look at more sophisticated radio interfaces, such as multiple-antenna phased arrays for readers, and tunnel diode reflection for tags. We will discuss the integration of information from Artificial Intelligence (AI)-based image processing, barcodes, NFC and UHF tags, into a digital twin of the real environment experienced by the human user. We will examine the role of RFID with sensing in improving the management of perishable goods. The role that RFID might play in a truly circular economy, with intelligent recycling and reuse, will be discussed. Finally, we survey the many hazards and obstacles that obstruct the path to an RF-informed future.

Memory-less and Backscatter-less Tunnel Diode Harmonic Signatures for RFID

Tunnel diodes have traditionally been researched for extending backscatter read-ranges for ultra-high-frequency (UHF) radio-frequency identification (RFID) tags as reflection amplifiers. This paper explores the natural harmonics that arise from biasing these diodes within their negative differential resistance regions and with no interrogating signal from a transmitting source, such as an RFID reader, to injection-lock these diodes. These harmonics are characterized for five tunnel diode boards, made with the same components and with each board's fundamental frequencies measuring at above -15 dBm at a biasing voltage of 200 mV when measured over-the-cable. The occurrence of these harmonics creates unique harmonic signatures for each board and demonstrates possible harmonic RFID applications that can help RFID readers discover and even identify RFID tags with backscatter-less and memory-less IDs generated by tunnel diodes.