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关键词： Accuracy   Transforms   Cameras   Sensors   Received signal strength indicator   Internet of Things   Passive RFID tags   Monitoring   Radiofrequency identification   Residual neural networks  

摘要： The rapidly developing Internet of things technology is gradually being utilized to monitor people's unhealthy behaviors. Sedentary behavior and wrong sitting posture are common health issues that can detrimentally impact the physical and psychological health of teenagers. An effective way to promptly rectify improper sitting postures among teenagers is to use equipment to monitor and recognize the alterations of sitting posture. The majority of conventional sitting posture recognition methods rely on cameras or sensors to recognize sitting posture. The employment of cameras will violate user's privacy, and the utilization of sensors will increase the cost of implementation.A dynamic sitting posture recognition system based on commodity off-the-shelf(COTS) radio frequency identification(RFID) devices is proposed. This system can recognize six common erroneous sitting postures by simply sticking five passive RFID tags on the user's back. We collect phase and received signal strength indicator(RSSI) data of passive RFID tags, then transform them into Doppler shift and RSSI difference data respectively, and finally input them into the established deep residual neural network for the classification of sitting postures. The experiment results show that our system achieves an average recognition accuracy of 99.17% with six sitting postures and is highly robust to different users and different usage environments.

关键词： Special issues and sections   Radiofrequency identification   Internet of Things   Wireless communication   Smart devices   Sensor systems  

关键词： Radio frequency identification (RFID)  

摘要： Human activity recognition (HAR) in indoor environments is essential for healthcare, elder care, and assisted living applications, especially in complex scenarios involving non-line-of-sight (NLoS) and long-range conditions. Traditional single-sensor HAR systems often struggle with accuracy and reliability in such environments. This study introduces the RFiDAR system, a novel fusion approach that combines radio frequency identification (RFID) and Radar technologies with an LSTM-variational autoencoder (LSTM-VAE) model to enhance HAR accuracy and reliability. The RFiDAR system applied data-level, feature-level, and decision-level fusion techniques to integrate temporal patterns from RFID and Radar data, facilitating the recognition of five distinct activities at varying distances. Results indicate that fusion methods, particularly feature-level fusion, significantly improve classification accuracy. For instance, feature-level fusion achieves up to 98.8% accuracy at 2 meters and 97.9% at 3 meters, outperforming single-sensor models by 5.3% and 6.2%, respectively. The RFiDAR system demonstrates superior performance in complex scenarios, offering reliable and cost-effective solutions for autonomous, long-term monitoring. The proposed approach has potential applications in healthcare and accessible IoT environments and demonstrates the innovative impact of multi-sensor fusion in developing safe, flexible, and inclusive technology. © 2018 IEEE.

关键词： Sensors   Apertures   Substrates   Inverters   Electromagnetics   Dielectric constant   Impedance   Reflection coefficient   Permittivity   Resonant frequency   Chipless-RFID   electromagnetic encoder   microstrip   motion sensor   phase-modulation sensor  

摘要： In this paper, a new electromagnetic encoder system for motion sensing and near-field chipless-RFID applications is presented. The system consists of an encoder, based on chains of transversally oriented linear apertures in a dielectric substrate, and a reader with an open-ended quarter-wavelength resonator that is sensitive to the presence of the apertures. The reader can detect variations in the phase of the reflection coefficient due to the motion of the encoder. To validate the encoder system, two encoders are implemented in a low-loss rigid substrate, and four are fabricated in flexible substrates, such as paper and plastic (polyethylene terephthalate -PET). One of the rigid encoders is incremental (with a periodic chain of apertures) and the other one is quasi-absolute (with two aperture sizes), useful for both motion sensing and near-field chipless-RFID. For the encoders implemented in flexible substrates (quasi-absolute in all cases), the apertures are replaced with linear chains of small holes, with a period of p = 2.3 mm. The resulting density of bits per unit length is DPL = 4.35 bit/cm. Such encoders provide a means to implement cost-effective and eco-friendly ("green") systems.

关键词： Resonant frequency   Metals   Training   Data mining   Artificial intelligence   Monitoring   Symbols   Surface cracks   Sensitivity   Radio spectrum management   Chipless radio frequency identification (RFID)   metal crack sensor   polarization multiplexing  

摘要： In this article, a metal crack sensor based on chipless radio frequency identification (RFID) technology is proposed. It is used to monitor the angle and width of cracks in the Internet of Things (IoT). The sensor is composed of square, rectangular, and bow-tie patches and operate within the frequency range of 3.5-7 GHz. By using polarization multiplexing and a modified bow-tie patch, the sensitivity of the sensor is improved. The results show that the sensor can accurately identify the cracks along the directions of 0 degrees, 45 degrees, 90 degrees, and 135 degrees. The corresponding sensitivity in each direction is 50.20 MHz/0.1 mm, 23.50 MHz/0.1 mm, 50.41 MHz/0.1 mm, and 33.88 MHz/0.1 mm. The sensor has the characteristics of passive, low-cost, and simple structure.

关键词： 复合绝缘子   红外   射频识别   反向传播神经网络   动态补偿  

摘要： 为解决红外热像仪在监测复合绝缘子异常升温时多重环境因素导致的测温精度不足的问题，提出一种联合射频识别（RFID）测温系统和红外热像仪的动态补偿方法。所提方法以RFID测温系统实时获得的精确温度作为标定值，结合环境温度、湿度和距离参数，并引入反向传播神经网络对红外测温结果进行动态补偿，从而实现对复合绝缘子全局温度的精确监测。实验结果表明，该模型的决定系数为0.99964，平均绝对误差为0.10951℃，均方根误差为0.15866℃，利用所提模型进行温度补偿后，红外测温的平均相对误差从9.62%降低至0.41%，测温精度从±2.26℃提高至±0.10℃，显示出良好的补偿性能。研究有效解决了红外测温技术的精度瓶颈问题，为复合绝缘子的状态监测和故障诊断提供了更可靠的技术支持。

关键词： Bandwidth  

摘要： A low-profile, compact symmetric dipole planar tag antenna with a single-layer structure is developed for UHF RFID applications on metal surfaces. It incorporates a patch-loaded interconnected arm configuration to enable a wide frequency tuning range. The antenna can be fabricated on a cost-effective FR4 substrate without shorting stubs or metallic vias. It has dimensions of 40 mm ×38 mm ×1.57 mm (0.122λ ×0.116λ ×0.004λ). The design features four interconnected arms with individual loading patches, which contribute to maintaining a broader bandwidth while enabling wide-range frequency tuning from 860 MHz to 960 MHz, the entire UHF RFID passband. By adjusting the width of the shorting patches between the arms and the loading patches, the antenna’s capacitive coupling is modified, which in turn alters the input reactance and enables precise tuning of the tag's resonant frequency. This tuning approach enables resonance adjustment across the UHF range without additional lumped components. The antenna is designed to maintain an optimal impedance matching with the microchip throughout the entire wideband tuning range. When operating at an effective isotropic radiated power (EIRP) of 4 W, the proposed tag antenna achieves a maximum reading distance of approximately 9 meters. Moreover, this design offers a compact, tunable, and cost-effective solution to improve RFID reliability in metal-mount environments. © 2017 IEEE.

关键词： Read range   RFID power profiles   RFID tag design   UHF-RFID  

摘要： This paper introduces comprehensive methodologies for optimizing UHF RFID performance over-the-air. The primary objective is to enhance the effectiveness of UHF RFID tags by maximizing the mean power transmission coefficient and modulation factor, crucial intrinsic characteristics. Through a systematic investigation within a predefined (√M,τ), (Q, γ) chart, we delve into these attributes, exploring their interplay. For a given chip, we establish and illustrate the valid domain, showcasing optimal antenna impedance choices. The culmination of this process is visually depicted by transforming the chart into the impedance plane, effectively highlighting antenna impedances that concurrently maximize both the mean power transmission coefficient and the modulation factor. © 2017 IEEE.

关键词： Wine  

摘要： Radio Frequency Identification (RFID) technology emerges as a crucial tool for passive sensing due to the lightweight, taggable, and easily deployable attributes of tags. However, RFID multi-tag systems face significant accuracy degradation due to tag mutual coupling interference. To address this problem, we propose the RF-Copy method, a tagged coupling interference suppression approach. The method constructs RSSI and phase models with coupled terms, simplifies and estimates these parameters based on the models, and develops an interference suppression algorithm to remove coupling effects and extract 'clean' signal fingerprints. Experimental results demonstrate that the decoupled outputs (0.318 dB RSSI, 0.623 radians phase) closely approach the interference-free baseline values (0.392 dB, 0.649 radians). We apply the RF-Copy method to evaluate the tag mutual coupling suppression effectiveness in nondestructive white wine and wine concentration recognition. This process generates 'clean' RSSI and phase values, which serve as input features for training a Gated Recurrent Unit (GRU) neural network integrated with an attention mechanism. Experimental results demonstrate that our method achieves unopened-package detection accuracies of 99.0% (white wine) and 99.6% (wine). Compared to other methods, the RF-Copy-GRU not only improves sensing accuracy but also demonstrates robustness against interference. © 2002-2012 IEEE.

关键词： Antennas   Radiofrequency identification   Resonance   Integrated circuits   Patch antennas   Impedance   UHF antennas   Resonant frequency   Equivalent circuits   Antenna measurements   UHF tag antenna   zeroth order resonance   meandered lines   on-metal tag antenna  

摘要： For the first time, two sections of planar meandered lines are incorporated with a compact C-shaped patch structure for designing a zeroth-order tag antenna that can be applied on metallic platforms. The proposed antenna operates at a resonance frequency of 0.915 GHz, which falls within the US UHF RFID (0.902 - 0.928 GHz). The meandered lines can introduce sufficient inductances for enabling the zeroth-order resonance. Also, the line dimension can be adjusted to tune the tag resonant frequency effectively. An analysis of the antenna's characteristics was carried out through unit cell simulation. It has been found that the zeroth-order resonance can be successfully excited even with the inclusion of the microchip. The proposed tag antenna is compact ( $20\times 40\times 1.6$ mm3), and it has a broadside read pattern with a long distance of up to 11.29 m at EIRP 4 W. When tested on various metal objects, the proposed tag has demonstrated consistent read performances.