A non-contact IC card reader/writer device includes antennas that perform carrier wave transmission and reception with a non-contact IC card, an A/D converter that detects the voltage level of each carrier wave received from the non-contact IC card through the antennas, and a control unit that calculates...http://www.google.com.tw/patents/US20040195324?utm_source=gb-gplus-share專利 US20040195324 - Non-contact IC card reader/writer device, non-contact IC card, input device, and method of calculating location of non-contact IC card
