For achieving a small size battery-less wireless keyboard for mobile devices, UHF RFID system is the most pertinent solution. A foldable keyboard using UHF RFID tags without any requirement for assited power was developed by KIITC. But its main limitation is the short reading range.
In this thesis, a compact (1.5cm $\times$ 1.8cm) RFID tag antenna has been designed to use in Korean UHF RFID band (910 $\sim$ 914 MHz) for this battery-less wireless keyboard. To increase the radiation resistance of the small size antenna, odd symetric structure of dipole antenna is chosen. The antenna is designed on a flexible PCB and has optimal bandwidth with Korean UHF RFID standard. To optimize the antenna on various materials, tunning method is also proposed. The reading range of antenna with RFID tag chip is measured over 2.5m in normal environment. Applying the propoesd tuning method, a range of over 60cm is achieved in a typical keyboard.