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关键词： Antenna measurements   Robots   Location awareness   Phase measurement   Antennas   Three-dimensional displays   Optimization   RFID   3D localization   nonlinear optimization   phase unwrapping   performance evaluation   robotics   SLAM  

摘要： In this paper, we present a prototype method for 3D localization of UHF RFID tags by a moving robot. The proposed method represents an extension of Phase ReLock, in 3D space. Phase measurements are collected by at least two antennas, thus a multi-antenna synthetic aperture is created. We propose a new optimization problem, which involves measurements from all different antennas. Thanks to phase-unwrapping, the new multi-antenna optimization problem preserves its convex-like properties. Consequently, it is solved rapidly by standard optimization techniques. Furthermore, we introduce a confidence metric that can identify measured data, which deteriorate the accuracy of the estimations. These can be removed from the measurements' dataset. We have conducted extensive measurements, employing four antennas on top of a SLAM-enabled robot;i.e., the robot is able to create a map of the unknown environment and continuously estimate its pose inside the map. The proposed method outperforms prior art with respect to accuracy and computation time. It achieves mean 3D error less than 20cm with an estimation-time of only 0.17s per tag on an average laptop.

关键词： Wearable antenna   circular polarization   passive UHF RFID tag   wearable RFID tag   wireless body-area systems  

摘要： We present a wearable passive UHF RFID tag based on a circularly polarized (CP) patch antenna on a textile substrate. The antenna miniaturization is based on applying a combination of the cross- and L-shaped slots in the radiator. In conjunction, the right-hand circular polarization is achieved by asymmetrically truncating all four corners of the square-shaped radiator. Despite using a regular low-permittivity textile as the antenna substrate, we downsized the antenna to a 5 cm x 5 cm footprint with the thickness of 4 mm, which is equal to 0.1525 lambda x 0.1525 lambda x 0.0091 lambda, where lambda is the free space wavelength at 915 MHz. In the numerical modeling and optimization of the antenna, we used a simplified cuboid-shaped and anatomical human body models. In addition to simulated conventional antenna performance indicators, we introduce spatial coverage as a new parameter for assessing the detection reliability of UHF RFID tags. Finally, we measured a manufactured tag worn in four different configurations on the body. The measured axial ratio value was approximately 2 dB in all cases and the tag provided a high attainable read range of around 5.8 meters for a right-hand CP reader emitting 3.28 W EIRP.

关键词： data filtering   dynamic clustering   energy efficiency   mobile RFID networks  

摘要： Data filtering is an essential task for improving the energy efficiency of radio-frequency identification (RFID) networks. Among various energy-efficient approaches, clustering-based data filtering is considered to be the most effective solution because data from cluster members can be filtered at cluster heads before being sent to base stations. However, this approach quickly depletes the energy of cluster heads. Furthermore, most previous studies have assumed that readers are fixed and interrogate mobile tags in a workspace. However, there are several applications in which readers are mobile and interrogate fixed tags in a specific area. This article proposes a model for dynamic clustering-based data filtering (DCDF) in mobile RFID networks, where mobile readers are re-clustered periodically and the cluster head role is rotated among the members of each cluster. Simulation results show that DCDF is effective in terms of balancing energy consumption among readers and prolonging the lifetime of the mobile RFID networks.

关键词： Radiofrequency identification   Radio frequency   Interference   Computer architecture   Baseband   Field programmable gate arrays   Backscatter   UHF RFID interrogator   interference cancellation   self-jamming   carrier leakage canceler   passive sensor system  

摘要： In this letter, we propose a fast self-jamming cancellation (SJC) architecture for Ultra High Frequency (UHF) radio-frequency identification (RFID) interrogators. The core SJC architecture includes a Field Programmable Gate Array (FPGA) as the RFID baseband processor, a radio frequency (RF) agile transceiver which has two transmitting ports as the RF front-end, and a combiner. By detecting the amplitude and phase of the interference carrier, the SJC algorithm transmits a suppression carrier through the second transmitting port of the agile RF transceiver. The suppression carrier could effectively suppress the self-jamming carrier without designing complex circuits. Our test results showed the isolation between the transmitting and receiving port achieves 100dB at UHF band, and the cancellation processes can be finished within 0.4ms.

关键词： biomedical engineering   environmental engineering   numerical simulations   occupational exposure   public health   specific energy absorption rate (SAR)   RadioFrequency IDentification (RFID)   Real-Time Location Systems (RTLS)   Internet of Things (IoT)   Personal Protective Equipment (PPE)  

摘要： The aim of this study was to model and evaluate the Specific Energy Absorption Rate (SAR) values in humans in proximity to fixed multi-antenna I-RFID readers of passive tags under various scenarios mimicking exposure when they are incorporated in Real-Time Location Systems (RTLS), or used to monitor Personal Protective Equipment (PPE). The sources of the electromagnetic field (EMF) in the modelled readers were rectangular microstrip antennas at a resonance frequency in free space of 866 MHz from the ultra-high frequency (UHF) RFID frequency range of 865-868 MHz. The obtained results of numerical modelling showed that the SAR values in the body 5 cm away from the UHF RFID readers need consideration with respect to exposure limits set by international guidelines to prevent adverse thermal effects of exposure to EMF: when the effective radiated power exceeds 5.5 W with respect to the general public/unrestricted environments exposure limits, and with respect to occupational/restricted environments exposure limits, when the effective radiated power exceeds 27.5 W.

关键词： Noise measurement   Radiofrequency identification   Mixers   Gain   Switches   Radio frequency   Degradation   Active leakage canceller (ALC)   leakage cancellation   power amplifier (PA)   radio frequency identification (RFID)  

摘要： A low-noise active leakage canceller (ALC) for radio frequency identification (RFID) transceiver is reported. The proposed ALC suppresses the strong transmitter (TX) leakage at the receiver (RX) input through continuous leakage tracking by employing an I/Q harmonic rejection switched-capacitor digital power amplifier (I/Q HR SC DPA). Compared to the analog feedback loop-based ALC, the proposed ALC minimizes the noise figure (NF) degradation in the RX and eliminates the large-size passive components in the analog low pass filter, which leads to high RX sensitivity and small chip area. Implemented in a 55-nm CMOS, the proposed ALC suppresses -10 dBm TX leakage down to -47.2 dBm while degrading the RX NF by 0.4 dB at the offset frequency of 640 kHz.

关键词： Antennas   Radiofrequency identification   Dipole antennas   Antenna measurements   Layout   Fabrics   Wrist  

摘要： Novel Yagi-like antenna structures were investigated here to design a UHF-RFID wearable antenna. The textile antennas were designed to be integrated into a smart glove, together with a compact UHF-RFID reader. Parasitic elements, acting as either a reflector or directors, were included to focus the field out of the operator's hand, thereby limiting the radiation toward undesired directions. To predict and compare the performance of the proposed near-field antennas, the power-transfer efficiency was numerically computed as a function of the reader-tag distance.

关键词： Repeaters   Backscatter   Wireless sensor networks   Power demand   Frequency division multiplexing   Antenna measurements   Frequency measurement   Backscattering   Internet of Things (IoT)   negative differential resistance   radio frequency identification (RFID)   repeaters   tunnel diode  

摘要： The efficacy of the deployment of backscatter networks in sensor networks and the internet of things has been severely limited by the maximum read range of backscatter radio frequency identification (RFID) tags. The work presented here demonstrates a low-power two-way repeater architecture capable of increasing the read range and extending the coverage of tags to non-line-of-sight (NLOS) scenarios. This is achieved through the use of a two-way frequency divided tunnel diode-based reflection amplifier optimized for use in backscattering channels. The system reports a more than 2X increase in the read range of a semi-passive RFID tag at 17 dBm output power. The work presented here shows a system capable of giving a comparable performance with the state of the art while consuming up to 1000X less power in a simple single-component front end.

关键词： RFID   localization   tracing   fine-scale positioning   long-range backscattering   tunneling tag   IoT  

摘要： This work demonstrates the ability to extend the positioning range of low-powered RFID tags to distances usually not achievable with other wireless or conventional RFID technologies. The technique is performed through a Received Signal Phase (RSP)-based method on a 5.8 GHz backscatter tunneling tag, in multipath-rich indoor and outdoor environments, at distances up to 35 meters from the reader. Distance errors as low as 0.1% of the total reader-to-tag distance were observed with average errors of 0.8% and 0.6% for indoor and outdoor environments, respectively. Compared to Received Signal Strength (RSS)-based techniques, the average distance estimation accuracy is improved by a factor of 51 and 38 for indoor and outdoor environments, respectively. Moreover, an Effective Isotropic Radiated Power (EIRP) of only 10.5 dBm and a biasing power for the tunneling tag of only 21.3 mu W at 80 mV promise a low-power, long-range sub-meter scale positioning technique with a projected maximum range over 1 km.

关键词： Medium access control  

摘要： In this paper, we propose a framework for cross-layer analysis of multi-static passive RFID systems. The model takes into account details of the shared wireless channel, including fading and capture effect, whereas, at the medium access control (MAC) layer, the anti-collision mechanism proposed in the EPC Generation 2 standard is taken as a reference. To address the complexity of the system model, we rely on a semi-analytical approach, that combines a moment matching approximation method to abstract the physical layer and Monte-Carlo simulations to describe the MAC dynamics. Furthermore, based on the space diversity feature offered by the multi-static settings, we introduce the concept of capture diversity and propose a modification to the standard to fully support this form of diversity. Numerical results show the impact of deployment conditions and the relative positions of interrogator, tags, and detection points on the performance of tags’ identification. We show how the number of detection points impacts the system performance under various channel conditions and MAC parameters’ settings. Finally, we validate the proposed update of the MAC protocol, showing substantial performance improvement with respect to the standard collision resolution policy. © 2021, CC BY.