Design and optimization of a rectangular microstrip patch antenna for dual-band 2.45 GHz/ 5.8 GHz RFID application

This paper introduces a new rectangular slot antenna structure based on a simple rectangular shape with two symmetrical rectangular slots on the radiated element. The aim of this work is to design an antenna and enhance it to function in the band (2.45 GHz and 5.8 GHz). We formulated the dimensions of the antenna using the transmission line model of the analytical methods and then we optimized these parameters using the CST Microwave Studio simulator. We made changes to two important parameters in our design: the position and width of the slots when the other parameters are kept constant. The resulting antenna provides good adaptation, high gain that achieves 5.96 dBi at 2.45 GHz and 6.491 dBi at 5.8 GHz, good return loss values of -49.859 dB and -34.303 dB for the lower and upper operating frequencies respectively. For radio frequency identification (RFID) implementations, the proposed antenna is ideal, and its main advantage is that it has high gain and is simple to design and fabricate

An analysis of the fundamental constraints on low cost passive radio-frequency identification system design

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (leaves 110-115).Passive radio frequency identification (RFID) systems provide an automatic means to inexpensively, accurately, and flexibly capture information. In combination with the Internet, which allows immediate accessibility and delivery of information, passive RFID systems will allow for increased productivities and efficiencies in every segment of the global supply chain. However, the necessary widespread adoption can only be achieved through improvements in performance - including range, speed, integrity, and compatibility - and in particular, decreases in cost. Designers of systems and standards must fully understand and optimize based on the fundamental constraints on passive RFID systems, which include electromagnetics, communications, regulations, and the limits of physical implementation. In this thesis, I present and analyze these fundamental constraints and their associated trade-offs in view of the important application and configuration dependant specifications.by Tom Ahlkvist Scharfeld.S.M

Application of Ultra-Wideband Technology to RFID and Wireless Sensors

Aquesta Tesi Doctoral estudia l'ús de tecnologia de ràdio banda ultraampla (UWB) per sistemes de identificació per radiofreqüència (RFID) i sensors sense fils. Les xarxes de sensors sense fils (WSNs), ciutats i llars intel•ligents, i, en general, l'Internet de les coses (IoT) requereixen interfícies de ràdio simples i de baix consum i cost per un número molt ampli de sensors disseminats. UWB en el domini temporal es proposa aquí com una tecnologia de radio habilitant per aquestes aplicacions. Un model circuital s'estudia per RFID d'UWB codificat en el temps. Es proposen lectors basats en ràdars polsats comercials amb tècniques de processat de senyal. Tags RFID sense xip (chipless) codificats en el temps son dissenyats i caracterizats en termes de número d'identificacions possible, distància màxima de lectura, polarització, influència de materials adherits, comportament angular i corbatura del tag. Es proposen sensors chipless de temperatura i composició de ciment (mitjançant detecció de permitivitat). Dos plataformes semipassives codificades en temps (amb un enllaç paral•lel de banda estreta per despertar el sensor i estalviar energia) es proposen com solucions més complexes i robustes, amb una distància de lectura major. Es dissenya un sensor de temperatura (alimentat per energia solar) i un sensor de diòxid de nitrogen (mitjançant nanotubs de carboni i alimentat per una petita bateria), ambdòs semipassius amb circuiteria analògica. Es dissenya un multi-sensor semipassiu capaç de mesurar temperatura, humitat, pressió i acceleració, fent servir un microcontrolador de baix consum digital. Combinant els tags RFID UWB codificats en temps amb tecnologia de ràdar de penetració del terra (GPR), es deriva una aplicació per localització en interiors amb terra intel•ligent. Finalment, dos sistemes actius RFID UWB codificats en el temps s'estudien per aplicacions de localització de molt llarg abast.Esta Tesis Doctoral estudia el uso de tecnología de radio de banda ultraancha (UWB) para sistemas de identificación por radiofrecuencia (RFID) y sensores inalámbricos. Las redes de sensores inalámbricas (WSNs), ciudades y casas inteligentes, y, en general, el Internet de las cosas (IoT) requieren de interfaces de radio simples y de bajo consumo y coste para un número muy amplio de sensores diseminados. UWB en el dominio temporal se propone aquí como una tecnología de radio habilitante para dichas aplicaciones. Un modelo circuital se estudia para RFID de UWB codificado en tiempo. Configuraciones de lector, basadas en rádar pulsados comerciales, son propuestas, además de técnicas de procesado de señal. Tags RFID sin chip (chipless) codificados en tiempo son diseñados y caracterizados en términos de número de identificaciones posible, distancia máxima de lectura, polarización, influencia de materiales adheridos, comportamiento angular y curvatura del tag. Se proponen sensores chipless de temperatura y composición de cemento (mediante detección de permitividad). Dos plataformas semipasivas codificadas en tiempo (con un enlace paralelo de banda estrecha para despertar el sensor y ahorrar energía) se proponen como soluciones más complejas y robustas, con una distancia de lectura mayor. Se diseña un sensor de temperatura (alimentado por energía solar) y un sensor de dióxido de nitrógeno (mediante nanotubos de carbono y alimentado por una batería pequeña), ambos semipasivos con circuitería analógica. Se diseña un multi-sensor semipasivo capaz de medir temperatura, humedad, presión y aceleración, usando un microcontrolador digital de bajo consumo. Combinando los tags RFID UWB codificados en tiempo y tecnología de radar de penetración de suelo (GPR), se deriva una aplicación para localización en interiores con suelo inteligente. Finalmente, dos sistemas activos RFID UWB codificados en tiempo se estudian para aplicaciones de localización de muy largo alcance.This Doctoral Thesis studies the use of ultra-wideband (UWB) radio technology for radio-frequency identification (RFID) and wireless sensors. Wireless sensor networks (WSNs) for smart cities, smart homes and, in general, Internet of Things (IoT) applications require low-power, low-cost and simple radio interfaces for an expected very large number of scattered sensors. UWB in time domain is proposed here as an enabling radio technology. A circuit model is studied for time-coded UWB RFID. Reader setups based on commercial impulse radars are proposed, in addition to signal processing techniques. Chipless time-coded RFID tags are designed and characterized in terms of number of possible IDs, maximum reading distance, polarization, influence of attached materials, angular behaviour and bending. Chipless wireless temperature sensors and chipless concrete composition sensors (enabled by permittivity sensing) are proposed. Two semi-passive time-coded RFID sensing platforms are proposed as more complex, more robust, and longer read-range solutions. A wake-up link is used to save energy when the sensor is not being read. A semi-passive wireless temperature sensor (powered by solar energy) and a wireless nitrogen dioxide sensor (enabled with carbon nanotubes and powered by a small battery) are developed, using analog circuitry. A semi-passive multi-sensor tag capable of measuring temperature, humidity, pressure and acceleration is proposed, using a digital low-power microcontroller. Combining time-coded UWB RFID tags and ground penetrating radar, a smart floor application for indoor localization is derived. Finally, as another approach, two active time-coded RFID systems are developed for very long-range applications

1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface

A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance

Beam scanning by liquid-crystal biasing in a modified SIW structure

A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium

Antenna Design with Characteristic Mode Analysis for Internet of Things Applications

PhDThe TV white space (TVWS) is one of the promising technologies to provide wide coverage, energy effcient and cost effective Internet of Things (IoT) services. However, its low operating frequency and wide bandwidth poses significant challenges to antenna designs. In this thesis, three antennas are developed using the characteristic mode analysis (CMA) for IoT devices operating over the TVWS. First, a very-low profile circular small antenna is transformed from a vertical monopole antenna. The CMA is used to determine the mode to be excited and to design a specific feeding structure. After being printed on Rogers 5880 substrate, the final antenna structure operates at 474 MHz with a V SWR < 2 bandwidth of 2.2 MHz. Its lateral radius is just 5.2% of the wavelength of its resonant frequency. Second, a compact U-shaped printed UWB monopole antenna is proposed to operate over the entire UHF TV spectrum. This antenna measures 0:36 0 0:06 0 0:01 0 where 0 is the wavelength of its lowest operating frequency. Its V SWR < 2 bandwidth is 87.5%, and the UWB behaviour is discussed by the CMA. Third, a novel antenna design method is established on annular ring-shaped structures with modal characteristics revealed by the CMA. Following the proposed method, another UWB antenna is achieved by creating and exciting multiple modes with resonant frequencies distributed across the UHF TV spectrum. All antenna designs are verified thorough simulations and measurements. Furthermore, antennas are also integrated into IoT devices and their system performance is measured under different communication scenarios. The system measurements also verify the good propagation property and the abundant spectrum resource of the TVWS

Antenna and rectifier designs for miniaturized radio frequency energy scavenging systems

With ample radio transmitters scattered throughout urban landscape, RF energy scavenging emerges as a promising approach to extract energy from propagating radio waves in the ambient environment to continuously charge low power electronics. With the ability of generating power from RF energy, the need for batteries could be eliminated. The effective distance of a RF energy scavenging system is highly dependent on its conversion efficiency. This results in significant limitations on the mobility and space requirement of conventional RF energy scavenging systems as they operate only in presence of physically large antennas and conversion circuits to achieve acceptable efficiency. This thesis presents a number of novel design strategies in the antenna and rectifier designs for miniaturized RF energy scavenging system. In the first stage, different energy scavenging systems including solar energy scavenging system, thermoelectric energy scavenging system, wind energy scavenging system, kinetic energy scavenging system, radio frequency energy scavenging system and hybrid energy scavenging system are investigated with regard to their principle and performance. Compared with the other systems, RF energy scavenging system has its advantages on system size and power density with relatively stable energy source. For a typical RF energy scavenging system, antenna and rectifier (AC-DC convertor) are the two essential components to extract RF energy and convert to usable electricity. As the antenna occupies most of the area in the RF energy scavenging system, reduction in antenna size is necessary in order to design a miniaturized system. Several antennas with different characteristics are proposed in the second stage. Firstly, ultra-wideband microstrip antennas printed on a thin substrate with a thickness of 0.2 mm are designed for both half-wave and full-wave wideband RF energy scavenging. Ambient RF power is distributed over a wide range of frequency bands. A wideband RF energy scavenging system can extract power from different frequencies to maximize the input power, hence, generating sufficient output power for charging devices. Wideband operation with 4 GHz bandwidth is obtained by the proposed microstrip antenna. Secondly, multi-band planar inverted-F antennas with low profile are proposed for frequency bands of GSM 900, DCS 1800 and Wi-Fi 2.4 GHz, which are the three most promising frequency bands for RF energy scavenging. Compared with previous designs, the triple band antenna has smaller dimensions with higher antenna gain. Thirdly, a novel miniature inverted-F antenna without empty space covering Wi-Fi 2.4 GHz frequency band is presented dedicated for indoor RF energy scavenging. The antenna has dimensions of only 10 × 5 × 3.5 mm3 with appreciable efficiency across the operating frequency range. In the final stage, a passive CMOS charge pump rectifier in 0.35 μm CMOS technology is proposed for AC to DC conversion. Bootstrapping capacitors are employed to reduce the effective threshold voltage drop of the selected MOS transistors. Transistor sizes are optimized to be 200/0.5 μm. The proposed rectifier achieves improvements in both power conversion efficiency and voltage conversion efficiency compared with conventional designs. The design strategies proposed in this thesis contribute towards the realization of miniaturized RF energy scavenging systems

Digital Beamforming Techniques for Passive UHF RFID Tag Localization

Radio-frequency identification (RFID) technology is on the way to substitute traditional bar codes in many fields of application. Especially the availability of passive ultra-high frequency (UHF) RFID transponders (or tags) in the frequency band between 860 MHz and 960 MHz has fostered the global application in supply chain management. However, the full potential of these systems will only be exploited if the identification of objects is complemented by accurate and robust localization. Passive UHF RFID tags are cost-effective, very small, extremely lightweight, maintenancefree, rugged and can be produced as adhesive labels that can be attached to almost any object. Worldwide standards and frequency regulations have been established and a wide infrastructure of identification systems is operated today. However, the passive nature of the technology requires a simple communication protocol which results in two major limitations with respect to its use for localization purposes: the small signal bandwidth and the small allocated frequency bandwidth. In the presence of multipath reflections, these limitations reduce the achievable localization accuracy and reliability. Thus, new methods have to be found to realize passive UHF RFID localization systems which provide sufficient performance in typical multipath situations. In this thesis, an enhanced transmission channel model for passive UHF RFID localization systems has been proposed which allows an accurate estimation of the channel behaviour to multipath. It has been used to design a novel simulation environment and to identify three solutions to minimize multipath interference: a) by varying the channel interface parameters, b) by applying diversity techniques, c) by installation of UHF absorbers. Based on the enhanced channel model, a new method for tag readability prediction with high reliability has been introduced. Furthermore, a novel way to rate the magnitude of multipath interference has been proposed. A digital receiver beamforming localization method has been presented which uses the Root MUSIC algorithm for angulation of a target tag and multipath reducing techniques for an optimum localization performance. A new multiangulation algorithm has been proposed to enable the application of diversity techniques. A novel transmitter beamforming localization approach has been presented which exploits the precisely defined response threshold of passive tags in order to achieve high robustness against multipath. The basic technique has been improved significantly with respect to angular accuracy and processing times. Novel experimental testbeds for receiver and transmitter beamforming have been designed, built and used for verification of the localization performance in real-world measurements. All the improvements achieved contribute to an enhancement of the accuracy and especially the robustness of passive UHF RFID localization systems in multipath environments which is the main focus of this researc

Experimental Characterisation of Body-Centric Radio Channels Using Wireless Sensors

PhDWireless sensors and their applications have become increasingly attractive for industry, building automation and energy control, paving the way for new applications of sensor networks which go well beyond traditional sensor applications. In recent years, there has been a rapid growth in the number of wireless devices operating in close proximity to the human body. Wearable sensor nodes are growing popular not only in our normal living lifestyle, but also within healthcare and military applications, where different radio units operating in/on/off body communicate pervasively. Expectations go beyond the research visions, towards deployment in real-world applications that would empower business processes and future business cases. Although theoretical and simulation models give initial results of the antenna behaviour and the radio channel performance of wireless body area network (WBAN) devices, empirical data from different set of measurements still form an essential part of the radio propagation models. Usually, measurements are performed in laboratory facilities which are equipped with bulky and expensive RF instrumentation within calibrated and controllable environments; thus, the acquired data has the highest possible reliability. However, there are still measurement uncertainties due to cables and connections and significant variations when designs are deployed and measured in real scenarios, such as hospitals wards, commercial buildings or even the battle field. Consequently, more flexible and less expensive measurement tools are required. In this sense, wireless sensor nodes offer not only easiness to deploy or flexibility, but also adaptability to different environments. In this thesis, custom-built wireless sensor nodes are used to characterise different on-body radio channels operating in the IEEE 802.15.4 communication standard at the 2.45 GHz ISM band. Measurement results are also compared with those from the conventional technique using a Vector Network Analyser. The wireless sensor nodes not only diminished the effect of semi-rigid or flexible coaxial cables (scattering or radiation) used with the Vector Network Analyser (VNA), but also provided a more realistic response of the radio link channel. The performance of the wireless sensors is presented over each of the 16 different channels present at the 2.45 GHz band. Additionally, custom-built wireless sensors are used to characterise and model the performance of different on-body radio links in dynamic environments, such as jogging, rowing, and cycling. The use of wireless sensors proves to be less obstructive and more flexible than traditional measurements using coaxial cables, VNA or signal generators. The statistical analysis of different WBAN channels highlighted important radio propagation features which can be used as sport classifiers models and motion detection. Moreover, specific on-body radio propagation channels are further explored, with the aim to recognize physiological features such as motion pattern, breathing activity and heartbeat. The time domain sample data is transformed to the frequency domain using a non-parametric FFT defined by the Welch’s periodogram. The Appendix-Section D explores other digital signal processing techniques which include spectrograms (STFT) and wavelet transforms (WT). Although a simple analysis is presented, strong DSP techniques proved to be good for signal de-noising and multi-resolution analysis. Finally, preliminary results are presented for indoor tracking using the RSS recorded by multiple wireless sensor nodes deployed in an indoor scenario. In contrast to outdoor environments, indoor scenarios are subject to a high level of multipath signals which are dependent on the indoor clutter. The presented algorithm is based on path loss analysis combined with spatial knowledge of each wireless sensor