Bidirectional Communication in an HF Hybrid Organic/Solution-Processed Metal-Oxide RFID Tag

A bidirectional communication protocol allows radio-frequency identification (RFID) tags to have readout of multiple tags in the RF field without collision of data. In this paper, we realized bidirectional communication between a reader system and thin-film RFID tag by introducing a novel protocol for the uplink communication. Amplitude modulation on the 13.56-MHz base carrier is used to transmit the uplink clock, whereas the data is modulated by varying pulsewidths on this clock. The technology for the thin-film RFID tags combines metal-oxide n-type transistors with organic p-type transistors resulting in a hybrid complementary technology flow. The design of the RFID tag comprises of two metal-oxide transistor rectifiers and a comparator to decode the data transmitted by the reader and different code generators that send 8 bits or 96 bits to the reader.