Measurement results for multichannel transmit beamforming tag direction detection in passive ultra-high frequency radio-frequency identification systems

Abstract

As an alternative to classical ultra-high frequency (UHF) radiofrequency identification (RFID) tag localisation methods (e.g. angle of arrival or received signal strength), a new angle-of-Activation approach is presented that uses digital multichannel transmit beamforming. By pivoting the main lobe of the interrogator's transmit antenna array utilising the very sensitive response threshold of passive UHF RFID tags, the tag direction is estimated. The presented three-channel digital beamforming hardware pivots the main lobe of a circularly polarised antenna array in a range of ±52 with an angular resolution of 0.02. It estimates the direction of a circularly polarised tag with a mean measured accuracy of 0.9 in a basic multipath environment.