Ubiquitous display
Electronic paper (e-paper) is proposed to being the display interface of radio frequency identification (RFID) smart card. The main feature of e-paper is zero power consumption of normal operation for data display. Only while changing display contents, e-paper needs electric power input. That makes it's a suitable solution for adding display function on a smart card but no needs for embedding a battery additionally. E-paper keeps display without power demands during normal operation. While changing display, it's just the same time that RFID tag chip communicates with reader side to exchange dealing information. E-paper can get power through wireless power transmission accompanied with RFID data exchange and change display contents for users' inspections such like a surplus of money stored in the card or the last dealing record. While the advantage of zero power consumption, but e-paper needs high driving voltage to change its display. It's difficult to achieve by wireless power transmission especially considering interference problems between power transmission and RFID data communication. In this study, a wireless power transmission system includes power emitter on the RFID reader side and coil antenna that attached on the smart card constructed to achieve near field coupling and high efficiency power transfer. A special AC driving schema was developed for effective e-paper driving. That means changing display should be completed in less than 1 sec, just the time to complete data exchange of RFID system. The novel system with the special driving schema was proved successful working and no interferences with RFID communications. The most important is that e-paper driving by wireless power transmission gives a display interface on a smart card. People can easily inspect data stored in RFID smart card in everywhere and anytime but not just have a brief view as they passed the reader. The purpose of ubiquitous display can be achieved.