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关键词： Sensors   Chipless RFID   Medical services   Radiofrequency identification   Sensor phenomena and characterization   Internet of Things   Biomedical monitoring   Tagging   Wearable devices   Healthcare   health monitoring   Internet of Things (IoT)   non-contact sensing   radio frequency identification (RFID)   wearable tags  

摘要： The demand for low-cost healthcare solutions has been increasing and the use of Internet of Things (IoT) devices is becoming more common. IoT devices have the potential to monitor vital health parameters of patients remotely, providing early detection of health problems and reducing medical costs. Chipless RFID sensors, combined with IoT technology, offer cost-effective solutions for healthcare applications. These sensors have significance for remote data collection, object tracking, authentication, and security. In recent years, there has been a growing attention on the design and development of chipless sensors for monitoring health. This paper provides an extensive review of chipless RFID sensors, including their functioning, fabrication techniques, and classifications. The paper further addresses the various smart sensing materials used in chipless RFID sensors, along with challenges and future trends. The IoT-based health monitoring system permits patients to be tracked 24/7 and provides rapid health consultations from doctors in distant places. The technology also allows guardians or family members to remotely monitor patients, which is regarded as one of the most significant benefits of saving human lives. Overall, this review article provides a comprehensive investigation of the potential advantages of chipless RFID sensors and IoT-based systems for healthcare monitoring, paving the way for cost-effective, easily accessible, and reliable healthcare solutions.

关键词： UHF-RFID RSSI and phase measurements   Kalman filtering   electromagnetic coupling  

摘要： We consider the close relative motion of two UHF RFID tags and the problem is the estimation of the distance between the two tags, by measuring the Received Signal Strength Indicator (RSSI) and the phase of the RFID signal backscattered by one of the two tags. Due to the short distance considered, and hence to the electromagnetic coupling between the antennas, the measured RSSI and phase present a complex and ambiguous dependence on the distance between the tags. The problem is solved through two approaches, based respectively on a Multi-Hypothesis Extended and a Multi-Hypothesis Unscented Kalman Filter (MHEKF and MHUKF). The availability of phase and RSSI allows to mitigate the ambiguity in the problem and to estimate the distance without any information on its initial value. Simulation and experimental results show the effectiveness of the approach, with the MHUKF presenting slightly better performances compared to the MHEKF. The proposed setup can be applied in manufacturing, robotics, safety and in any context where the variable distance between two close objects should be monitored.

关键词： Sensors   Resonant frequency   Encoding   Resonators   Radar cross-sections   RFID tags   Frequency measurement   Chipless RFID tags   concentric resonators   circular rings   encoding capacity   radar cross section   sensing  

摘要： This paper introduces an innovative strategy for the development of sensing-ready concentric rings-based chipless radio frequency identification (CRFID) tags. Our approach is marked by the novel use of exponentially increasing spacing, a significant departure from the conventional uniform spacing method. This innovative design results in an impressive 88.2% improvement in tag data encoding capacity compared to traditional designs. Importantly, our design framework not only advances the current state of CRFID tag technology but also methodically lays the foundation for future integration of high-resolution sensing capabilities. This is achieved by strategically utilizing the innermost ring as a prospective sensing site, complemented by the implementation of nulls for data encoding achieved through the addition of an extra ring at the tag's outermost edge. Notably, all these features represent advancements that have not been demonstrated in previously published concentric rings-based CRFID tags. To empirically validate our methodology, we have developed and tested 18-bit example tags optimized for operation within the ultrawideband (UWB) spectrum, covering a range from 3.1 to 10.6 GHz. The radar cross-section (RCS) response of these tags exhibits well-distributed resonances, culminating in a high encoding capacity of 17.65 bits/ $\lambda <^>{2}$ /GHz. Preliminary results using capacitors connected to the innermost ring underscore the future sensing potential of our tags, setting the stage for more advanced sensing implementations in subsequent research.

关键词： 射频识别   传感器   Modbus   消防系统  

摘要： 针对公路隧道内消防器材数量较大，设施维护成本高和消防环境监测依赖人工等具体消防需求，文章设计使用多种传感器组成的硬件系统实现对消防设备和消防环境的实时监测以及可靠的通讯协议保证数据传输，并分层、分模块地设计了软件的功能和结构，用以实现智能化、自动化的隧道消防监测系统。实验结果表明，该系统具有良好的可靠性和稳定性，能够有效提高隧道消防能力。

关键词： Sensors   Monitoring   Sleep apnea   Sensor systems   Sensitivity   Coils   Wireless sensor networks   Ballistocardiography (BCG)   energy harvesting   flexible electronics   near-field communication (NFC)   noninvasive monitoring   passive system   printed electronics   radio frequency identification (RFID)  

摘要： This work presents an innovative approach employing passive radio frequency identification (RFID) technology to develop a comprehensive ballistocardiography (BCG) system for contactless and noninvasive vital sign monitoring of individuals on a mattress. The method relies on wireless energy transfer through inductive coupling at 13.56 MHz between an active powering board and a passive, flexible sensing board with dimensions of 12.6 x 4.7 cm(2). Both boards face each other at a separation distance of 3 cm. The system demonstrates remarkable sensitivity to mattress vibrations resulting from bodily movements, rendering it proficient in generating complete BCG signals capable of discerning heart rate (HR), breathing rate (BR), and activity. Practical trials with six healthy subjects validated the feasibility and efficacy of the system, showing an average absolute error of 1.8 beats/min for HR and 0.6 breaths/min for BR. Unlike conventional BCG systems, the sensing module seamlessly integrates into the mattress side. This is leveraged to enable the simultaneous monitoring of two subjects on a queen-size mattress, taking advantage of the local sensitivity of the sensing mechanism. Extracted BCG values can be wirelessly transmitted to the user's smartphone through near-field communication (NFC) and to a cloud service used for storage, distribution, and categorization of subject data. This work establishes a foundation for future extensive studies and applications, as the obtained BCG signals could provide health-related insights, such as detecting heart diseases, respiratory problems, or evaluating sleep quality.

关键词： 无线无源传感器   后向散射   RFID   方向回溯天线阵  

摘要： 为了满足日益发展的物联网技术以及日趋复杂的应用场景对传感器提出的更高的要求,无线无源传感器正在被人们广泛研究。相较于传统的有线传感器和无线有源传感器而言,无线无源传感器的成本更低,体积更小,能具有更复杂多变的应用场景,在应用场景中固定后即可配合读取系统长久使用,使用寿命更长且无需更换。根据上述优点,本文以基于后向散射的无线无源传感器的相关理论进行展开,以不同原理的无线无源传感架构的设计为研究方向,共设计了两款基于射频识别(Radio Frequency Identification,RFID)的无线无源传感架构和一款有潜力应用于无线无源传感系统中的方向回溯天线阵,具体工作如下: (1)提出了基于相位变化的无线无源传感架构,原理是架构中传感部分的反射系数相位会随着环境参数的变化而改变,并附加在架构的后向散射信号上,这种相位变化可以在阅读器上被读取并还原环境参数的变化。架构工作在915MHz,包含单极子天线、环行器、芯片及其匹配网络以及利用热敏电阻进行温度传感的传感部分。在实测中传感灵敏度为0.47°/1℃,温度升高1℃,传感器端相位增加0.47°,最佳工作距离在5m以内。这种架构可以不改变其他成分,只改变传感部分来得到不同类型的传感器。 (2)提出了基于幅度变化的无线无源传感架构,该架构原理是传感部分的反射系数幅度会随着环境参数的改变而发生变化,而芯片匹配网络部分的反射系数不会改变,后向散射信号的相位与二者的比值具有一定关系,据此来实现传感功能。该架构工作在915MHz,包括天线、芯片及匹配网络、传感部分以及电桥与功分器组成的网络,在实测中该架构的传感灵敏度为0.75°/1℃,温度升高1℃,传感器端相位增加0.75°,最佳工作距离在2.5m以内。该架构也具有普适性,即只需更换传感部分就可获得不同类型的传感器,为实现无线无源传感器提供了一种方案。 (3)提出了一种基于Van Atta天线阵的方向回溯天线阵,对该方向回溯天线阵进行了仿真分析,该方向回溯天线阵在入射角为-35°35°内可以实现方向回溯功能,并且该阵列具有变极化的特性。其方向回溯特性和变极化的特性使其拥有更远的工作距离,该阵列具有应用在无线无源传感系统中的潜力。

关键词： Hash functions  

摘要： RFID technology offers an affordable and user-friendly solution for contactless identification of objects and individuals. However, the widespread adoption of RFID systems raises concerns regarding security and privacy. Vulnerabilities such as message tampering, interception, and eavesdropping pose significant risks to the integrity of the system. This study examines the effectiveness of two recently proposed ultra-lightweight RFID authentication protocols, URASP and KUAJB, in addressing these security challenges. Surprisingly, our findings reveal that both URASP and KUAJB protocols are susceptible to secret disclosure attacks, despite their claims of providing robust security. Consequently, the development of a truly ultra-lightweight protocol that ensures adequate security becomes a formidable task. As a potential solution, the enhancement of the URASP protocol through the integration of a simple cryptographic primitive is suggested to bolster its security measures. © 2013 IEEE.