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关键词： capacitive sensor   radio-frequency identification (RFID)   interdigitated electrode capacitor (IDC)   ultrahigh frequency (UHF)   sensitivity   zero-power sensor   grounded coplanar waveguide (GCPW)   battery-less   wireless sensor  

摘要： In this paper, a new method for the wireless detection of liquid level is proposed by integrating a capacitive IDC-sensing element with a passive three-port RFID-sensing architecture. The sensing element transduces changes in the liquid level to corresponding fringe-capacitance variations, which alters the phase of the RFID backscattered signal. Variation in capacitance also changes the resonance magnitude of the sensing element, which is associated with a high phase transition. This change in the reactive phase is used as a sensing parameter by the RFID architecture for liquid-level detection. Practical measurements were conducted in a real-world scenario by placing the sensor at a distance of approximately 2 m (with a maximum range of about 7 m) from the RFID reader. The results show that the sensor node offers a high sensitivity of 2.15 degrees/mm to the liquid-level variation. Additionally, the sensor can be used within or outside the container for the accurate measurement of conductive- or non-conductive-type liquids due to the use of polyethylene coating on the sensitive element. The proposed sensor increases the reliability of the current level sensors by eliminating the internal power source as well as complex signal-processing circuits, and it offers real-time response, linearity, high sensitivity, and excellent repeatability, which are suitable for widespread deployment of sensor node applications.

关键词： coplanar waveguide   metamaterial   reflection   transmission coefficients   RFID  

摘要： In this study, split ring resonator (SRR) based coplanar waveguide (CPW) fed antenna for 5.8 GHz radio frequency identification applications is presented. The antenna has a compact size of 18 x 12 x 0.8 mm(3) on an FR-4 substrate. The proposed antenna has been simulated in HFSS 2019 R2 EM simulator. Scattering parameter retrieval method has been used for the analysis of metamaterial unit cells. Return loss, E-plane and H-plane radiation patterns of the proposed antenna have been analyzed. The proposed antenna provides good radiation efficiency of 97.5% at an ISM frequency of 5.8 GHz.

关键词： Antennas   backscattering   biodegradable   CMOS   energy harvesting   green substrates   harmonic transponders   MTT 70th Anniversary Special Issue   recyclable electronics   rectifier   RFID   system-on-chip   sustainable IoT   wireless power transmission  

摘要： This invited paper presents potential solutions for tackling some of the main underlying challenges toward developing sustainable Internet-of-things (IoT) devices with a focus on eco-friendly manufacturing, sustainable powering, and wireless connectivity for next-generation IoT devices. The diverse applications of IoT systems, such as smart cities, wearable devices, self-driving cars, and industrial automation, are driving up the number of IoT systems at an unprecedented rate. In recent years, the rapidly-increasing number of IoT devices and the diverse application-specific system requirements have resulted in a paradigm shift in manufacturing processes, powering methods, and wireless connectivity solutions. The traditional cloud-centering IoT systems are moving toward distributed intelligence schemes that impose strict requirements on IoT devices, e.g., operating range, latency, and reliability. In this article, we provide an overview of hardware-related research trends and application use cases of emerging IoT systems and highlight the enabling technologies of next-generation IoT. We review eco-friendly manufacturing for next-generation IoT devices, present alternative biodegradable and eco-friendly options to replace existing materials, and discuss sustainable powering IoT devices by exploiting energy harvesting and wireless power transfer. Finally, we present (ultra-)low-power wireless connectivity solutions that meet the stringent energy efficiency and data rate requirements of future IoT systems that are compatible with a batteryless operation.

关键词： Chipless radio frequency identification (CRFID)   frequency-domain (FD)   miniaturization   open-loop   radar cross section (RCS)   resonators   tag  

摘要： In this paper, a unique structural design methodology for chipless radio-frequency identification (RFID) tags in frequency domain is presented. The tag geometry is developed by loading an open-loop resonator with micro-metallic-cells (MMC). The realization give rise to a checkerboard resonator type with electromagnetic signatures in its radar cross section that are extremely efficient to manipulate. The resonators layout is distributed on either side of a Rogers substrate to double its coding density. The proposed chipless RFID tag has a memory of 8-bits in total. The operating band of the tag is 6.5-10.5 GHz. The tag has a high bit coding density of 10.94 bits/cm(2) and spectral efficiency of 2 bits/GHz. The tag has a very compact size of 17.4 x 4.2 mm(2). The simple structuring methodology and efficient resonators layout will give RFID system designers the flexibility to apply the proposed tag in a wide range of modern applications.

关键词： Automotive   clutter suppression   D-band   fre-quency doubler   frequency-modulated continuous wave (FMCW)   harmonic   millimeter-wave (mm-wave)   monolithic microwave integrated circuit (MMIC)   radar   radio frequency identification (RFID)   SiGe   tag   vulnerable road users   W-band  

摘要： Although traffic safety continues to improve overall, fatalities of vulnerable traffic participants and pedal cyclists specifically have reached 30-year highs. While automotive radar sensors continue to advance and are integrated in more and more vehicles, they are not ideally suited to detect pedal cyclists, especially in complicated traffic scenarios. To mitigate the problem of the lower radar-cross section (RCS) of the cyclist, equipping them with harmonic radio frequency identification (RFID) tags is proposed. The presented system showcases the benefits of this approach by being able to conduct conventional automotive radar measurements and detect tags simultaneously. In this work, we present the printed-circuit boards (PCBs) and the necessary chipset, while especially focusing on the design of a power-efficient harmonic RFID tag. By improving the gain per current of an amplifier chain, the tag enables a range sufficient for urban scenarios while consuming little enough current to be powered by battery-operated lights. This enables the detection of pedal cyclists even in complicated scenarios at a distance of up to 80 m.

关键词： Resonators  

摘要： This paper proposes a compact multi-bits chipless RFID tag using fully printed resonators with dual performance of tagging and sensing temperature. Each bit is modelled as curl resonator coupled to microstrip line and is printed on metal-backed Rogers RO4003 substrate. The proposed model is characterized by high attenuation of - 10 dB with narrow bandwidth and power reflection of - 3.2 dB. A parametric study on the effect of the tag dimensions of the transmission coefficient response is introduced. The resonance frequency of each bit is controlled via controlling the curl arm's length. The multi-bits RFID tag is modelled using multi-curl resonators arranged next to microstrip line with different arm lengths. A multi-bits chipless RFID tags with 3-bits, 6-bits and 12-bits are designed in the frequency band from 3 to 7 GHz. The dimensions of 6-bits code are 60 x 17 mm(2) and for 12-bits code are 29.75 x 34 mm(2). A temperature sensing capability is achieved via integrated Stanyl polyamide material with the curl resonator. The first bit is used for temperature sensing while the other bits are used for data encoding. The proposed chipless RFID tags are simulated using commercial software based on well defined numerical techniques;i.e. high-frequency structure simulator (HFSS) based on finite element method (FEM) and verified with CST-microwave studio (CST-MWS) based on the finite integral technique (FIT).

关键词： Impedance   Dipole antennas   Photodiodes   Antennas   Geometry   Broadband antennas   Resistance   Microwave antennas   photodiodes   RFID  

摘要： A planar antenna structure based on a folded asymmetrical dipole is presented, whose geometrical parameters are seen to independently determine either the real or the imaginary parts of the complex radiation impedance. This unique feature allows very efficient and wideband conjugate matching coupling to nonconventional RF sources of arbitrary internal impedance, i.e., small resistance with large and negative reactance. The antenna theoretical framework is developed and an optimized design to match a photodiode is manufactured and measured. The results show a fractional bandwidth of about 20% in the 28 GHz band.

关键词： Location awareness   Radiofrequency identification   Monitoring   Apertures   Tomography   Synthetic aperture radar   Rails   Device-free localization (DFL)   synthetic aperture radar (SAR)   received signal strength (RSS)   rapid-moving   UHF-RFID  

摘要： Exploring and developing the perception system is an important means to promote the development of intelligent transportation. In this paper, we propose RAPP, a radio tomography-based method enabling performance parameterization to achieve parameter adjustment of localization accuracy without dense deployment of passive UHF RFID devices. The reader antenna takes a rapid-moving system as the carrier and generates virtual antenna elements to inventory received signal strength (RSS) of the pre-deployed tags. To eliminate the impact of the lack of tag backward signals during the mobile process and supplement the link distribution for each segment of the monitored platform, the Cubic Spline Interpolation algorithm (CSIA) is proposed to homogenize the spacing of the virtual antenna elements by preprocessing the measurements. Then the optimized link information is adopted to perform radio tomographic imaging to recognize the locations of targets. Theoretical analysis on ill-condition is derived to analyze how the number of virtual interpolation elements affects the localization accuracy. Further derivation about the relationship between the Bayesian Cramer-Rao Bound (CRB) and the link density provides a solution to influence the localization performance through parameter adjustment. Extensive simulation and experiment show that RAPP outperforms on multiple targets localization and behaves robustly in a multipath environment.

关键词： gesture recognition   RFID   tags   signal processing  

摘要： Gesture recognition can help people with a speech impairment to communicate and promote the development of Human-Computer Interaction (HCI) technology. With the development of wireless technology, passive gesture recognition based on RFID has become a research hotspot. In this paper, we propose a low-cost, non-invasive and scalable gesture recognition technology, and successfully implement the RF-alphabet, a gesture recognition system for complex, fine-grained, domain-independent 26 English letters;the RF-alphabet has three major advantages: first, this paper achieves complete capture of complex, fine-grained gesture data by designing a dual-tag, dual-antenna layout. Secondly, to overcome the disadvantages of the large training sets and long training times of traditional deep learning. We design and combine the Difference threshold similarity calculation prediction model to extract digital signal features to achieve real-time feature analysis of gesture signals. Finally, the RF alphabet solves the problem of confusing the signal characteristics of letters. Confused letters are distinguished by comparing the phase values of feature points. The RF-alphabet ends up with an average accuracy of 90.28% and 89.7% in different domains for new users and new environments, respectively, by performing feature analysis on similar signals. The real-time, robustness, and scalability of the RF-alphabet are proven.

关键词： RFID   passive RFID tag   NB-IoT technology   specimen tube   specimen transport box  

摘要： In this study, we propose a specimen tube prototype and smart specimen transport box using radio frequency identification (RFID) and narrow band-Internet of Things (NB-IoT) technology to use in the Department of Laboratory Medicine, King Chulalongkorn Memorial Hospital. Our proposed method replaces the existing system, based on barcode technology, with shortage usage and low reliability. In addition, tube-tagged barcode has not eliminated the lost or incorrect delivery issues in many laboratories. In this solution, the passive RFID tag is attached to the surface of the specimen tube and stores information such as patient records, required tests, and receiver laboratory location. This information can be written and read multiple times using an RFID device. While delivering the specimen tubes via our proposed smart specimen transport box from one clinical laboratory to another, the NB-IoT attached to the box monitors the temperature and humidity values inside the box and tracks the box's GPS location to check whether the box arrives at the destination. The environmental condition inside the specimen transport box is sent to the cloud and can be monitored by doctors. The experimental results have proven the innovation of our solution and opened a new dimension for integrating RFID and IoT technologies into the specimen logistic system in the hospital.