Bidirectional communication in an HF hybrid organic/solution-processed metal-oxide RFID tag

\u3cp\u3eThe ambition of printing item-level RFID tags is one of the driving forces behind printed electronics research. Organic RFID tags have been shown, initially using p-type organic semiconductors [1-4]. The introduction of n-type organic semiconductors with reasonable performance made organic CMOS conceivable [5] and organic CMOS RFID tags were shown [6]. However, all currently reported organic RFID tags are based on a tag-talks-first principle: as soon as the tag gets powered from the RF field, its code is transmitted at a data rate determined by an internal ring oscillator. Practical RFID systems will need to be able to read multiple RFID tags within the reach of the reader antenna. Existing anti-collision protocols implemented in organic RFID tags [2,4] are limited to about maximum 4 tags and come at the cost of a slow reading time. In this paper, we for the first time realize a reader-talks-first low-temperature thin-film transistor (TFT) RFID circuit. We use a complementary hybrid organic/oxide technology. As organic transistors with reasonable channel lengths (≥2μm) have a cut-off frequency below 13.56MHz, the base carrier frequency of HF communication, present technologies on foil do not yet allow to extract the circuit clock as a fraction of the base carrier. We solve this by introducing an original uplink (reader-to-tag) scheme, in which a slow clock (compatible with our transistors' speed) is transmitted as amplitude-modulation on the base carrier while data is encoded on this clock by pulse width modulation (PWM).\u3c/p\u3

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. cop. 1963-2012 IEEE

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

The ambition of printing item-level RFID tags is one of the driving forces behind printed electronics research. Organic RFID tags have been shown, initially using p-type organic semiconductors [1-4]. The introduction of n-type organic semiconductors with reasonable performance made organic CMOS conceivable [5] and organic CMOS RFID tags were shown [6]. However, all currently reported organic RFID tags are based on a tag-talks-first principle: as soon as the tag gets powered from the RF field, its code is transmitted at a data rate determined by an internal ring oscillator. Practical RFID systems will need to be able to read multiple RFID tags within the reach of the reader antenna. Existing anti-collision protocols implemented in organic RFID tags [2,4] are limited to about maximum 4 tags and come at the cost of a slow reading time. In this paper, we for the first time realize a reader-talks-first low-temperature thin-film transistor (TFT) RFID circuit. We use a complementary hybrid organic/oxide technology. As organic transistors with reasonable channel lengths ( >2 um) have a cut-off frequency below 13.56MHz, the base carrier frequency of HF communication, present technologies on foil do not yet allow to extract the circuit clock as a fraction of the base carrier. We solve this by introducing an original uplink (reader-to-tag) scheme, in which a slow clock (compatible with our transistors' speed) is transmitted as amplitude-modulation on the base carrier while data is encoded on this clock by pulse width modulation (PWM).status: publishe

Investigation of Variation in Organic Thin-film Transistors (OTFT) and Design of Variation-aware Organic Circuits

This work investigates the key sources of variability in OTFT namely process variations and bias-stress induced variation, and presents circuit design techniques to build robust variation-aware digital and analog circuits using OTFT. OTFT suffer from a relatively large Vt variation due to the bias stress effects, and process mismatch variations. Though these effects are also prevalent in silicon based transistors, their magnitude is comparatively larger in the case of OTFT. This renders the well-established silicon based circuits unsuitable for organic electronics. Therefore, direct adaptation of the silicon based circuits for realising organic circuits does not effectively handle the relatively large parameter and mismatch variations associated with OTFT. In this work, we first investigate the bias-stress induced threshold voltage (Vt) variation and process variations to understand the impact of these variations on the performance of organic circuits. Then, two different strategies were employed to design robust organic circuits. The first method involves designing new load topologies that are more robust to the threshold voltage variations without compromising on gain. The other strategy was to realize the essential analog circuit functionalities like comparator, ADC using digital circuit blocks. In this direction, a digital comparator and digital A/D converter circuits were developed. Finally to demonstrate the system integration, a temperature sensing organic smart label system was designed