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

Within the field of radio-frequency identification (RFID) research, tunnel diodes have traditionally been researched for extending backscatter read-ranges for ultra-high-frequency (UHF) RFID tags as reflection amplifiers due to their negative resistance. This same negative resistance can also be used to help construct oscillators. This paper further explores the use of tunnel diodes to make oscillators for harmonic RFID applications and the natural harmonics that arise when biasing these diodes within their negative differential resistance (NDR) regions and with no external injection-locking, interrogating signal from a transmitting source, such as an RFID reader. These harmonics are characterized for five tunnel diode boards, made with the same components, and with each board’s fundamental frequencies’ RF strength measuring at above –15 dBm at a biasing voltage of 200 mV when measured over-the-cable. The best DC-to-RF conversion efficiency achieved in this work was 30%. The occurrence of harmonics from the tunnel diodes creates unique harmonic signatures for each board and demonstrates possible harmonic RFID applications that involve RFID readers discovering and even identifying RFID tags with backscatter-less, hardware-intrinsic, and memory-less IDs generated by such tunnel diodes on these tags. Thus, these harmonic signatures provide alternative or complementary IDs to the traditional IDs stored in tags’ memory.