An improved radio frequency transponder has a reflector to increase its operative range. A system of one or more reflectors is operatively associated with a transponder and may be formed out of any sort of radio frequency reflective material. The reflector system can enhance reception or transmission...http://www.google.com.hk/patents/US6441740?utm_source=gb-gplus-share專利 US6441740 - Radio frequency identification transponder having a reflector
