RFID-polling devices exist for inventory and shopping related purposes. For example U.S. Pat. No. 8,305,192 RFID reader with automatic near/far field interrogation mode switching, and related operating methods U.S. Pat. No. 7,336,177 RFID system and method for tracking individual articles. U.S. Pat. No. 7,253,717 Armstrong Method and system for communicating with and tracking RFID transponders.
However they lack apparatus and methods for Homing, and homing through thousands of competing RFID fields of communications.
USPTO Backgrounds
USPTO Backgrounds