Indoor Measurement and Analysis for an Optimal Multi- Antenna Receiver of FM0-Based RFID Signal
- Indoor Measurement and Analysis for an Optimal Multi- Antenna Receiver of FM0-Based RFID Signal
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- The majority of current UHF passive RFID system employs for transmission and reception an omni-directional dipole antenna that is connected to a single transmit (Tx) RF chain and a single receive (Rx) RF chain through a circulator. In this case, the reception performance of tag may degrade because the location of tag in dead zone, multipath fading phenomenon, and/or faint backscattering by the tag result in a low signal-to-noise ratio (SNR) or a low signal-to-interference-plus-noise ratio (SINR).Unlike the conventional reader, the reader considered in this paper has multiple circular polarized antennas without circulator. Multiple Tx antennas can be employed to increase the azimuthal coverage of the reader Rx. The use of multiple Rx antennas can increase the coverage of the reader by enhancing received signal power and at the same time by suppressing co-channel interference, and also enables direction of arrival estimation. Also, theoretical analysis and practical measurement are performed in the variety of UHF passive RFID channel environment.The main activities of this paper are to construct an RFID testbed for UHF passive tag, to propose a theoretically optimized algorithm to improve tag’s reception performance, to implement the RFID testbed, to estimate the direction of arrival, to analyze and identify UHF passive RFID channel.First, an RFID testbed for UHF passive tag specifically designed to sound RFID channels is constructed in order to be utilized in the continuing research on systems with UHF passive tag. With this testbed, we perform indoor measurement campaign. Using these measurement results, we verify the integrity of the UHF passive RFID testbed. Second, we propose a multi-antenna receiver for FM0-based RFID signal and theoretically prove its optimality. The indoor measurement is utilized to analyze channel parameters and improve the reception performance of an RFID reader. Lastly, an estimator for direction of arrival is derived based on minimum output energy (MOE) beamforming. In addition, a channel identification method based on the SAGE-like algorithm is proposed.
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