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关键词： RFID   anti-collision   co-channel interference elimination   blind source separation   bounded component analysis  

摘要： Radio Frequency Identification (RFID) is one of the key technologies of the Internet of Things. However, during its application, it faces a huge challenge of co-frequency interference cancellation, that is, the tag collision problem. The multi-tag anti-collision problem is modeled as a Blind Source Separation (BSS) problem from the perspective of system communication transmission layer signal processing. In order to reduce the cost of the reader antenna, this paper uses the boundedness of the tag communication signal to propose an underdetermined RFID tag anti-collision method based on Bounded Component Analysis (BCA). This algorithm converts the underdetermined tag into the signal collision model is combined with the BCA mechanism. Verification analysis was conducted using simulation data. The experimental results show that compared with the nonnegative matrix factorization (NMF) algorithm based on minimum correlation and minimum volume constraints, the bounded component analysis method proposed in this article can perform better. Solving the underdetermined collision problem greatly improves the effect of eliminating co-channel interference of tag signals, improves the system bit error rate performance, and reduces the complexity of the underdetermined model system.

关键词： Radiofrequency identification   Antennas   Resonant frequency   Dual band   Antenna measurements   Metals   Impedance   UHF antennas   Semiconductor device measurement   Impedance measurement   Anti-metal tag antenna   dual-band tag antenna   split-ring resonator (SRR)   UHF radio frequency identification (RFID) tag antenna  

摘要： For the first time, an asymmetric split-ring resonator (SRR) is employed for designing a dual-band anti-metal tag antenna that can cover both the lower European (LEu) and North American (NA) UHF radio frequency identification (RFID) frequency ranges. It is intended to be applied on small metallic objects. The two frequency ranges are generated by concurrently exciting the even and odd modes of the asymmetric SRR, which has a shorting post at the middle of the split ring. Each operating frequency can be tuned independently without affecting the other much by adjusting the asymmetricity of the SRR as well as the lengths of the loading open stubs. Design equations have been derived for calculating the two operating frequencies. The proposed tag has a miniature size (40 x 30 x 1.653 mm or 0.1224 lambda x 0.0916 lambda x 0.00504 lambda at lambda(o) = 916 MHz), and it can be effectively read in the range of similar to 5 m (4 W effective isotropic radiated power-EIRP) on metal and similar to 2.5 m in air and on small metallic objects in the boresight direction (theta = 0 degrees) for both the frequency ranges, showing a stable frequency performance.

关键词： measurement   CCD   RFID   image processing   golden section   Harris corner detection  

摘要： To improve the performance of Radio Frequency Identification (RFID) multi-label systems, the multi-label network structure needs to be quickly located and optimized. A multi-label location measurement method based on the NLM-Harris algorithm is proposed in this paper. Firstly, multi-label geometric distribution images are obtained through a label image acquisition system of a multi-label semi-physical simulation platform with two vertical Charge-Coupled Device (CCD) cameras, and Gaussian noise is added to the image to simulate thermoelectric interference. Then, a fast NLM algorithm that optimizes the kernel coefficient acquisition speed is used for image denoising. Finally, the Harris corner algorithm is used to obtain the corner points of the images. After screening the diagonal points, the pixel coordinates of the preset origin and the four corners of the labels are obtained. Furthermore, the actual coordinates of the labels are obtained according to the pixel relationship. The results show that the average absolute errors of x, y, and z coordinates are 0.773 mm, 0.782 mm, and 0.807 mm, respectively. In addition, the relative errors are 1.659%, 2.260%, and 0.258%, which shows the high location accuracy of the multi-label network. It is of great significance to measure and optimize the performance of multi-label systems.

关键词： Chipless RFID   Gesture recognition   Backscatter   Radiofrequency identification   Frequency modulation   Resonant frequency   Real-time systems   Backscatter modulation   differential radar cross-section (RCS)   hand gesture recognition   motion-modulated chipless radio frequency identification (RFID)  

摘要： This article presents a real-time identification process for slow motion-modulated chipless radio frequency identification (RFID), which can be applied to human hand gestures to realize a full-practical long-range RFID system with gesture recognition capability. Depolarizing chipless tags configured by hand in three gestures are utilized, while different motion-induced modulation effects involved in each gesture are analytically modeled. The identification based on differential radar cross-section (RCS) and gesture recognition using deterministic in-phase/quadrature (IQ) trajectories is addressed according to the developed model. The fast reading process for slow motion-modulated chipless RFID is proposed based on the sequential fast frequency sweep acquisitions by vector network analyzer (VNA), while the sweep time is very short compared to the period of motion. The identification time achieved using this approach is about only a few periods of motion, which is ideal for implementing hand gesture-modulated chipless RFID in real time. The designed gesture-modulated chipless tag is identified during a few seconds at distances up to 3 m for the most efficient gesture. Moreover, all the hand gestures are recognized at the 2-m range based on the received IQ signature. These achievements realize the practical example of motion-modulated chipless RFID where both tag identification and gesture recognition are simultaneously provided.

关键词： Wireless sensing   Heartbeat estimation   RFID   Dynamic interference cancellation  

摘要： With the rapid development of smart health care, accurate heart rate variability (HRV) estimation for the early detection of diseases has become a hot research topic. Advanced work uses the wireless signal to estimate the heartbeat in a contact-free way, which usually cannot separate multiple users or work in a dynamic environment. In this article, we propose a lightweight heartbeat-sensing method based on RFID tag pairs, which focuses on HRV extraction in a more general sensing scenario. Based on the tag-pair design, we build a novel heartbeat and respiration model to describe the signal relationship between the two tags from the time and space domains. Based on the model, we propose a Calibrated Temporal-Spatial IQ-Shaping-based signal cancellation algorithm to cancel the respiration and extract the heartbeat. To remove the interference in dynamic measurement, we build an IQ-based signal model via a Principal Component Analysis-based interference estimation. To reduce the statistical error in HRV extraction, we further design a neural network to predict the HRV index. We have implemented a system prototype in a real environment with COTS RFID devices. Extensive experiments show that our system can achieve a median RMSSD error of 7.51 ms, which satisfies the medical demand in HRV measurement.

关键词： energy harvesting   RFID   passive sensor tag   reflection amplification   multi-source energy harvesting  

摘要： Wireless sensor networks often rely on battery power, which incurs high costs, considerable volume, and a limited lifespan. Additionally, the communication range of existing passive sensor tags remains short, which challenges their suitability for evolving Internet of Things (IoT) applications. This paper, therefore, presents a long-distance passive RFID sensing tag that integrates multi-source energy harvesting and reflection amplification. Multi-source energy harvesting enhances tag receiving sensitivity and extends the system's downlink communication distance, while reflection amplification increases tag reflection power and improves the uplink communication distance, thereby significantly expanding the overall communication range. The test results show that the tag achieves a receiving sensitivity of -45 dBm, a reflection gain of 44 dB, and a communication distance of up to 96 m.

关键词： Noise measurement   Antennas   Switches   Antenna feeds   Dipole antennas   Radiofrequency identification   Antenna arrays   UHF antennas   Magnetic resonance   Loop antennas   Far field (FF)   large area   near field (NF)   switchable feeding network   ultrahigh-frequency (UHF) radio frequency identification (RFID)  

摘要： In this letter, we present a switchable near-field (NF) and far-field (FF) antenna designed for ultrahigh-frequency (UHF) radio frequency identification applications. The antenna consists of a four-dipole array and a feeding network. By adjusting the current distribution through the multiport feeding network, the antenna can either create a strong, uniform magnetic field in the NF region with low FF gain or produce circularly polarized radiation in the FF region. Through the use of segmented lines and parasitic elements, the antenna achieves a flat magnetic field distribution over a large area. The NF and FF modes can operate independently or in polling. A prototype was fabricated and tested, showing that the antenna generates a strong, uniform magnetic field over an interrogation zone of 270 mm x 270 mm in NF mode, while delivering a 3.7 dBic gain in FF mode. These results confirm the antenna's excellent performance in both NF and FF regions, with an isolation of over -22 dB between the two modes.

关键词： RFID认证协议   混淆操作   分组循环操作   形式化验证  

摘要： 针对RFID系统中存在的隐私和安全问题，提出了一种基于新型混淆操作的超轻量RFID认证协议，通过利用简单的逐位异或、循环左旋转和新提出的超轻量化分组循环操作，达到低复杂度、高安全性的目的。此外，由于在协议交互过程中的消息根据随机数生成，攻击者无法通过穷举来破解消息。分析与验证结果表明，所提协议可以有效地抵御常见的网络攻击类型，并且在计算和存储成本方面具备优势。

关键词： Radiofrequency identification   Radar   Physiology   Millimeter wave radar   Biomedical monitoring   Trajectory   Accuracy   Heart beat   Receiving antennas   Neural networks   Identity   location   millimeter-wave radar   physiological signal   radio frequency identification (RFID)   trajectory  

摘要： One-to-one correspondence between life activities (such as breathing, heartbeat, and trajectory) and identity information is essential for accurately reflecting an individual's state. However, existing research often fails to achieve one-to-one matching of life activities and identity information when using wireless devices. In addition, millimeter-wave radar typically relies on pre-established datasets and neural networks to verify identity, which can be impractical in dynamic settings, such as meeting scenarios with frequent personnel changes. The accuracy of physiological signal detection via radio frequency identification (RFID) is also affected by the position and type of tags used. To address these limitations, this study proposes an algorithm for matching life activities and identity information called (M-LAII), which achieves static and dynamic information matching. It combines millimeter-wave radar and RFID for the first time, perceives physiological signal information and position information through millimeter-wave radar, perceives position information and identity information through RFID, and connects position information to match physiological signal (trajectory) information and identity information. The proposed algorithm offers several advantages: it can filter out nonhuman targets (removing environmental noise), maintain a consistent 100% accuracy in identity recognition, minimize positioning bias, decrease errors in physiological signal detection, and define unknown trajectories. M-LAII achieves one-to-one matching of identity, location, and physiological signal information, as well as one-to-one matching of identity and trajectory data, in multitarget scenarios. This approach eliminates the need for dataset creation and neural network construction and minimizes the impact of tag position and type on performance.

关键词： Radiofrequency identification   Antennas   Couplings   Application software   Meters   UHF antennas   Reviews   Internet of Things   Hands   Object recognition   AMC   cross-dipole   IoT   metasurface   PEC   RFID  

摘要： The internet of things (IoT) paradigm aims to make the world smarter by reducing human intervention and promoting automated interactions. A radio frequency identification (RFID) reader is a necessary component for automated object identification and data transfer in an IoT network. Its performance is primarily determined by the characteristics of the integrated or externally connected antennas. This article provides a review of the state-of-the-art reader antenna designs, as well as research challenges. The RFID reader antennas are investigated based on their operating frequency bands, gain, and polarization. Generalized procedures for designing specific antenna configurations, which are useful and widely used by readers, are illustrated and explained. Several design challenges have been investigated and analyzed, including narrow bandwidth, bidirectional radiation pattern, low gain, linear polarization, and a larger footprint. Subsequent solutions have also been provided. Cross-dipole configurations are one method for achieving a compact footprint and circular polarization characteristics without using complicated feeding circuitry. Low antenna gain has a direct impact on the read range of the reader. Therefore, increasing the gain of the reader antennas is an essential requirement. One of the gain-enhancing techniques is to use an artificial magnetic conductor (AMC) surface beneath the antenna. This reduces backward radiation of the antenna-AMC integrated configuration, increasing the antenna peak gain. The AMC also helps in the achievement of unidirectional radiation.