A far field radio frequency identification (RFID) tagging and tracking system employing a plurality of continuous wave (CW), unmodulated signals selected from frequencies including a predetermined frequency band, includes a RFID interrogator generating a group of CW unmodulated signals corresponding...http://www.google.com.au/patents/US7023342?utm_source=gb-gplus-sharePatent US7023342 - Continuous wave (CW)—fixed multiple frequency triggered, radio frequency identification (RFID) tag and system and method employing same
