Enhancing RFID Location Sensing Using a Dual Directional Antenna

Abstract

A location sensing radio frequency identification (RFID) system has been developed employing a single directional antenna. This system enabled a mobile robot to identify, locate, and approach a stationary transponder. However, since the system determined the bearing of the transponder by scanning the environment about the azimuth axis, it faced difficulties if the transponder was not stationary. Also, even though the accuracy was within a reasonable range, it may deteriorate in the case of occlusions and cluttered environments. In this paper, we propose a dual directional antenna system to enhance RFID location sensing in dynamically changing environments. The dual directional antenna is a set of two identical directional antennas perpendicularly positioned to each other having a phase difference. A mobile robot system equipped with the proposed antenna can determine the bearing of the transponder using the ratio of the signal strength between two antennas. The proposed system, not requiring rotation of the antenna, is available to track the heading of a moving transponder and can minimize the environmental effects causing signal distortions. To verify the robustness of the proposed system to any reflective or signal blocking obstacles and moving transponders, we perform experiments under various conditions with applications to mobile robot navigation. 1