Array signal processing for source localization and enhancement

“A common approach to the wide-band microphone array problem is to assume a certain array geometry and then design optimal weights (often in subbands) to meet a set of desired criteria. In addition to weights, we consider the geometry of the microphone arrangement to be part of the optimization problem. Our approach is to use particle swarm optimization (PSO) to search for the optimal geometry while using an optimal weight design to design the weights for each particle’s geometry. The resulting directivity indices (DI’s) and white noise SNR gains (WNG’s) form the basis of the PSO’s fitness function. Another important consideration in the optimal weight design are several regularization parameters. By including those parameters in the particles, we optimize their values as well in the operation of the PSO. The proposed method allows the user great flexibility in specifying desired DI’s and WNG’s over frequency by virtue of the PSO fitness function. Although the above method discusses beam and nulls steering for fixed locations, in real time scenarios, it requires us to estimate the source positions to steer the beam position adaptively. We also investigate source localization of sound and RF sources using machine learning techniques. As for the RF source localization, we consider radio frequency identification (RFID) antenna tags. Using a planar RFID antenna array with beam steering capability and using received signal strength indicator (RSSI) value captured for each beam position, the position of each RFID antenna tag is estimated. The proposed approach is also shown to perform well under various challenging scenarios”--Abstract, page iv

Antenna integration for wireless and sensing applications

As integrated circuits become smaller in size, antenna design has become the size limiting factor for RF front ends. The size reduction of an antenna is limited due to tradeoffs between its size and its performance. Thus, combining antenna designs with other system components can reutilize parts of the system and significantly reduce its overall size. The biggest challenge is in minimizing the interference between the antenna and other components so that the radiation performance is not compromised. This is especially true for antenna arrays where the radiation pattern is important. Antenna size reduction is also desired for wireless sensors where the devices need to be unnoticeable to the subjects being monitored. In addition to reducing the interference between components, the environmental effect on the antenna needs to be considered based on sensors' deployment. This dissertation focuses on solving the two challenges: 1) designing compact multi-frequency arrays that maintain directive radiation across their operating bands and 2) developing integrated antennas for sensors that are protected against hazardous environmental conditions. The first part of the dissertation addresses various multi-frequency directive antennas arrays that can be used for base stations, aerospace/satellite applications. A cognitive radio base station antenna that maintains a consistent radiation pattern across the operating frequencies is introduced. This is followed by multi-frequency phased array designs that emphasize light-weight and compactness for aerospace applications. The size and weight of the antenna element is reduced by using paper-based electronics and internal cavity structures. The second part of the dissertation addresses antenna designs for sensor systems such as wireless sensor networks and RFID-based sensors. Solar cell integrated antennas for wireless sensor nodes are introduced to overcome the mechanical weakness posed by conventional monopole designs. This can significantly improve the sturdiness of the sensor from environmental hazards. The dissertation also introduces RFID-based strain sensors as a low-cost solution to massive sensor deployments. With an antenna acting as both the sensing device as well as the communication medium, the cost of an RFID sensor is dramatically reduced. Sensors' strain sensitivities are measured and theoretically derived. Their environmental sensitivities are also investigated to calibrate them for real world applications.Ph.D.Committee Chair: Tentzeris, Emmanouil; Committee Member: Akyildiz, Ian; Committee Member: Allen, Mark; Committee Member: Naishadham, Krishna; Committee Member: Peterson, Andrew; Committee Member: Wang, Yan

DISTRIBUTED PHASED ARRAY ANTENNAS IN WIDE AREA RFID

Ultra High Frequency (UHF) Radio Frequency Identification (RFID) has gained importance over the past two decades in many applications such as stock management, asset tracking and access control. For wide area applications, Distributed Antenna Systems (DAS) have been used to obtain good coverage with few antennas by making use of multiple spatially distributed antennas and phase dithering. This implements a far-field beamforming that maximises the instantaneous power at a tag. Separately, phased array antennas have also been used to increase the read range by increasing the effective field of view of an antenna and overcoming multipath fading through beam steering. This dissertation explores a combination of both approaches to improve RFID read ranges in wide interrogation zones. Distributed antenna arrays are explored in the context of delivering high tag detection probabilities in a multi-cell RFID system, while maximising inter-antenna separations. A Distributed Antenna Array System (DAAS) is designed and shown to be capable of providing comparable performance to a fixed DAS system with fewer antennas. The properties of the system are further studied and its upper performance limit is explored by modelling a hypothetical perfectly steerable antenna array. The concept of using perfectly steerable arrays is further explored to propose a cell-less RFID system, in which cell allocation in wide area RFID is replaced with a tag location-based interrogation requiring the global reader antenna population to be used for interrogation of all tags, leading to significant potential increases in inter-antenna separation, and consequently good coverage with fewer antennas. It is also argued that this system leads to the avoidance of complex reader anti-collision policies, since only a single central reader is now required. Finally, the design of a wide-scan-angle antenna array is presented as a compromise solution for perfectly steerable antennas, whist still keeping the desired property of being flat panel. A 3D RFID multi-antenna model is presented and used for simulating and analysing the various described systems and for system planning

Location and Map Awareness Technologies in Next Wireless Networks

In a future perspective, the need of mapping an unknown indoor environment, of localizing and retrieving information from objects with zero costs and efforts could be satisfied by the adoption of next 5G technologies. Thanks to the mix of mmW and massive arrays technologies, it will be possible to achieve a higher indoor localization accuracy without relying on a dedicated infrastructure for localization but exploiting that designed for communication purposes. Besides users localization and navigation objectives, mapping and thus, the capability of reconstructing indoor scenarios, will be an important field of research with the possibility of sharing environmental information via crowd-sourcing mechanisms between users. Finally, in the Internet of Things vision, it is expected that people, objects and devices will be interconnected to each other with the possibility of exchanging the acquired and estimated data including those regarding objects identification, positioning and mapping contents. To this end, the merge of RFID, WSN and UWB technologies has demonstrated to be a promising solution. Stimulated by this framework, this work describes different technological and signal processing approaches to ameliorate the localization capabilities and the user awareness about the environment. From one side, it has been focused on the study of the localization and mapping capabilities of multi-antenna systems based on 5G technologies considering different technological issues, as for example those related to the existing available massive arrays. From the other side, UWB-RFID systems relying on passive communication schemes have been investigated in terms of localization coverage and by developing different techniques to improve the accuracy even in presence of NLOS conditions

Novel Passive RFID Temperature Sensors Using Liquid Crystal Elastomers

When transporting perishable foods in the Cold Supply Chain (CSC), it is essential that they are maintained in a controlled temperature environment (typically from -1° to 10°C) to minimize spoilage. Fresh-food products, such as, meats, fruits, and vegetables, experience discoloration and loss of nutrients when exposed to high-temperatures. Also, medicines, such as, insulin and vaccines, can lose potency if they are not maintained at the appropriate temperatures. Consequently, the CSC is critical to the growth of global trade and to the worldwide availability of food and health supplies; especially, when considering that the retail food market consists mostly (approximately 65%) of fresh-food products. The current method of temperature monitoring in the CSC is limited to discrete location-based measurements. Subsequently, this data is used to assess the overall quality of transported goods. As a result, this method cannot capture all the common irregularities that can occur during the delivery cycle. Therefore, an effective sensor solution to monitor such items is necessary. Radio Frequency Identification (RFID) is a pragmatic wireless technology with a standardized communication protocol. Thus far, passive RFID temperature sensors have been investigated. However, each design has a limitation from which a set of design guidelines for an improved sensor solution is developed. That is, the new sensor should: (a) be compact to be applicable on individual products, (b) utilize purely passive technology to ensure longevity and cost-effectiveness, (c) monitor goods in a continuous fashion (e.g., operate through multiple room-to-cold and cold-to-room temperature cycles), and (d) operate in an independent mode, so that no resetting is required. In this research, antenna systems and RF circuit design techniques are combined with Liquid Crystal Elastomers (LCEs) to develop three novel temperature sensors. LCEs are temperature responsive polymers that are programmable and reversible. Notably, LCEs return to their original state when the stimulus is removed. Also, for the first time, cold-responsive LCEs are incorporated into the designs presented in this research. Two of the developed sensors convey temperature changes through the controlled shift in the operating frequency. The third design conveys temperature threshold crossings by reversibly switching operation between two RFID ICs (or two Electronic Product Codes). Finally, all designs have been fabricated and tested with favorable results in accordance to the above mentioned guidelines

Ultra high frequency (UHF) radio-frequency identification (RFID) for robot perception and mobile manipulation

Personal robots with autonomy, mobility, and manipulation capabilities have the potential to dramatically improve quality of life for various user populations, such as older adults and individuals with motor impairments. Unfortunately, unstructured environments present many challenges that hinder robot deployment in ordinary homes. This thesis seeks to address some of these challenges through a new robotic sensing modality that leverages a small amount of environmental augmentation in the form of Ultra High Frequency (UHF) Radio-Frequency Identification (RFID) tags. Previous research has demonstrated the utility of infrastructure tags (affixed to walls) for robot localization; in this thesis, we specifically focus on tagging objects. Owing to their low-cost and passive (battery-free) operation, users can apply UHF RFID tags to hundreds of objects throughout their homes. The tags provide two valuable properties for robots: a unique identifier and receive signal strength indicator (RSSI, the strength of a tag's response). This thesis explores robot behaviors and radio frequency perception techniques using robot-mounted UHF RFID readers that enable a robot to efficiently discover, locate, and interact with UHF RFID tags applied to objects and people of interest. The behaviors and algorithms explicitly rely on the robot's mobility and manipulation capabilities to provide multiple opportunistic views of the complex electromagnetic landscape inside a home environment. The electromagnetic properties of RFID tags change when applied to common household objects. Objects can have varied material properties, can be placed in diverse orientations, and be relocated to completely new environments. We present a new class of optimization-based techniques for RFID sensing that are robust to the variation in tag performance caused by these complexities. We discuss a hybrid global-local search algorithm where a robot employing long-range directional antennas searches for tagged objects by maximizing expected RSSI measurements; that is, the robot attempts to position itself (1) near a desired tagged object and (2) oriented towards it. The robot first performs a sparse, global RFID search to locate a pose in the neighborhood of the tagged object, followed by a series of local search behaviors (bearing estimation and RFID servoing) to refine the robot's state within the local basin of attraction. We report on RFID search experiments performed in Georgia Tech's Aware Home (a real home). Our optimization-based approach yields superior performance compared to state of the art tag localization algorithms, does not require RF sensor models, is easy to implement, and generalizes to other short-range RFID sensor systems embedded in a robot's end effector. We demonstrate proof of concept applications, such as medication delivery and multi-sensor fusion, using these techniques. Through our experimental results, we show that UHF RFID is a complementary sensing modality that can assist robots in unstructured human environments.PhDCommittee Chair: Kemp, Charles C.; Committee Member: Abowd, Gregory; Committee Member: Howard, Ayanna; Committee Member: Ingram, Mary Ann; Committee Member: Reynolds, Matt; Committee Member: Tentzeris, Emmanoui

2012 PWST Workshop Summary

No abstract availabl

Radio frequency non-destructive testing and evaluation of defects under insulation

PhD ThesisThe use of insulation such as paint coatings has grown rapidly over the past decades. However, defects and corrosion under insulation (CUI) still present challenges for current non-destructive testing and evaluation (NDT&E) techniques. One of such challenges is the large lift-off introduced by thick insulation layer. Inaccessibility due to insulation leads corrosion and defects to be undetected, which can lead to catastrophic failure. Furthermore, lift-off effects due to the insulation layers reduce the sensitivities. The limitations of existing NDT&E techniques heighten the need for novel approaches to the characterisation of corrosion and defects under insulation. This research project is conducted in collaboration with International Paint®, and a radio frequency non-destructive evaluation for monitoring structural condition is proposed. High frequency (HF) passive RFID in conjunction with microwave NDT is proposed for monitoring and imaging under insulation. The small-size, battery-free and cost-efficient nature of RFID makes it attractive for long-term condition monitoring. To overcome the limitations of RFID-based sensing system such as effective monitoring area and lift-off tolerance, microwave NDT is proposed for the imaging of larger areas under thick insulation layers. Experimental studies are carried out in conjunction with specially designed mild steel sample sets to demonstrate the detection capabilities of the proposed systems. The contributions of this research can be summarised as follows. Corrosion detection using HF passive RFID-based sensing and microwave NDT is demonstrated in experimental feasibility studies considering variance in surface roughness, conductivity and permeability. The lift-off effects introduced by insulation layers are reduced by applying feature extraction with principal component analysis and non-negative matrix factorisation. The problem of thick insulation layers is overcome by employing a linear sweep frequency with PCA to improve the sensitivity and resolution of microwave NDT-based imaging. Finally, the merits of microwave NDT are identified for imaging defects under thick insulation in a realistic test scenario. In conclusion, HF passive RFID can be adapted for long term corrosion monitoring of steel under insulation, but sensing area and lift-off tolerance are limited. In contrast, the microwave NDT&E has shown greater potential and capability for monitoring corrosion and defects under insulation

Design And Practical Implementation Of Harmonic-Transponder Sensors

Harmonic radar is a nonlinear detection technology that transmits and receives radio-frequency (RF) signals at orthogonal frequencies, so as to suppress the undesired clutters, echoes and electromagnetic interreferences due to multipath scattering. Its implementation generally comprises a nonlinear tag (i.e, a harmonic transponder), which picks the interrogation signal at specific fundamental frequency (f0) and converts it into a high/sub-harmonic signal (nf0). Such a technology has been successfully applied to tracking small insects and detection of electrically-small objects in the rich-scattering environment. Similarly, a harmonic sensor is used to interrogate electrically-small and passive sensors, of which the magnitude and peak frequency of output harmonics (e.g., second harmonic) are functions of the parameter to be sensed. A harmonic tag or sensor comprises one or multiple antennas, a frequency modulator, a sensor, a microchip and matching networks. Here, we propose and experimentally validate compact, low-cost, low-profile, and conformal hybrid-fed microstrip antennas for the harmonics-based radar and sensor systems. The proposed 98 microstrip antennas are based on a simple single-layered and hybrid-feed structure. By optimizing the feed position and the geometry of microstrip patch, the fundamental mode and particular higher-order modes can be excited at the fundamental frequency and the second harmonic. We have derived the analytical expressions for calculating the antennas’ resonant frequencies, which have been verified with numerical simulations and measurements. Our results show that the proposed hybrid-feed, single-layered microstrip antennas, although having a compact size and a low profile, can achieve descent realized gain (1.2 – 3.5 dB), good impedance matching (return loss \u3c -15 dB), high isolation (\u3c-20 dB), and favorable co/cross-polarization properties. The proposed microstrip antennas may benefit various size-restricted harmonic transponders used for harmonic radars, harmonic sensors, medical implants, passive radio-frequency identification (RFID), and internet-of-things (IoT) applications

Realistic frequency coded chipless RFID: physically modulated tags and refectarray readers

In letzter Zeit hat die chiplose RFID Technologie enorme Aufmerksamkeit im besonders kostenbewussten Markt für Objektidentifikation erregt. Allerdings befindet sich der aktuelle Stand der Technik auf einem konzeptionellen Niveau und leidet noch unter einer Menge Einschränkungen, die eine sofortige Verwendung der Technologie noch verhindern. Grundsätzlich lässt sich ein chiploses RFID System in drei Teile unterteilen, dem RFID Lesegerät, den verwendeten Antennen und dem RFID Tag. Der Beitrag der vorliegenden Dissertation zur Überwindung der erwähnten Einschränkungen liegt in innovativen physikalisch modulierenden RFID Tags und in der Weiterentwicklung des Antennensystems des RFID Lesegerätes. Dabei werden besonders die drei im Folgenden beschriebenen Aspekte betrachtet. Der erste Aspekt beschäftigt sich mit physikalisch linear modulierten RFID Tags. Dabei werden die RFID Tags mit einem Ultra Breitband (engl. ultra wideband, UWB) Signal bestrahlt und die auf dem RFID Tag aufgebrachten Resonatoren modulieren die Frequenz des Signals physikalisch. Dabei werden dem UWB Signal resonante Notches und/oder Peaks aufmoduliert, die sich in der Frequenzantwort des von der effektiven Rückstrahlfläche (engl. radar cross section, RCS) zurückgestrahlten Signals befindet. Hierfür sind vier innovative physikalisch modulierende RFID Tags, mit dem Ziel einer effektiveren Kodierung und maximalen Kodierungstiefe bei gleichbleibender Frequenzauslastung und RFID Tag Größe, entwickelt worden. Der erste RFID Tag besteht aus ineinander verschachtelten Ringresonatoren, wobei jeder Resonator ein Notch, also ein Bit, erzeugt. Der zweite RFID Tag arbeitet auf zwei unterschiedlichen Polarisationsebenen für empfangene und rückgestrahlte Signale. Dadurch kann die Streustrahlung der Umgebung leichter herausgefiltert werden. Beide Strukturen sind skalierbar, druckbar und kompakt. Als drittes wird ein neuartiger Notchbreiten modulierender (engl. notch width modulation, NWM) RFID Tag eingeführt. Dabei ist die ID des RFID Tags nicht nur über die Notchlage im Frequenzbereich sondern auch über die Notchbreite definiert. Die Notchbreite stellt also eine zusätzliche Dimension bereit, die die Freiheitsgrade (engl. degree of Freedom, DoF) für Kodierung und Modulation erhöhen, was wiederum die kodier Effektivität und Codetiefe verbessert. Als letztes wird ein neuartiger On Off-Notch/Peak (OONP) und Notch/Peak-Position (N/P-P) modulierender RFID Tag eingeführt. Die Idee dahinter ist, sowohl das kopolarisierte als auch das kreuzpolarisierte Rückstrahl Signal eines mit einer linear-polarisierten Welle angeregten RFID Tags auszunutzen. Dies bittet ein weiteres Kriterium um sowohl kodier Effektivität als auch Codetiefe des chiplosen RFID Systems weiter zu verbessern. Gleichzeitig verbessert die kreuzpolarisierte Antwort auch wieder die Detektion des RFID Tags in einer realen Umgebung. Alle vorgeschlagenen RFID Tags und Modulationsschemata sind mit elektromagnetischen (EM) Simulationen und in einer realen Testumgebung überprüft worden. Der zweite Aspekt dieser Arbeit schlägt Reflect-Array Antennen (RA) für das RFID Lesegerät mit dem Ziel vor, die Lesereichweite zu erhöhen und die Reflektionen an der Umgebung zu minimieren. Das RA bietet dabei im Vergleich zu herkömmlichen Phased-Array-Antennen eine Menge weiterer Eigenschaften. Das RA ist einfach zu integrieren, von geringem Gewicht, hat eine sehr geometrische Anordnung und ist preiswert, um nur einige zu nennen. Insgesamt wurden drei neuartige RA Aufbauten entwickelt. Als erstes wurde eine logarithmisch periodische Antenne (engl. log periodic antenna array, LPDA) als Primärstrahler für die entworfene RA Oberfläche genutzt. Der Prototype arbeitet bei 5.8GHz und erreicht eine Bandbreite von 300MHz. Außerdem ist der erzeugte Antennenstrahl viermal schmaler als der Primärstrahl und erreicht somit einen um 6dB höheren Antennengewinn bei einem Nebenkeulenpegel (engl. side lobe level, SSL) von −10dB. Für den zweiten Prototypen wird ein selbstentwickelter Hornstrahler mit konstanter Phase als Primärstrahler für die RA Oberfläche verwendet. Durch diese Anordnung wird ein UWB RA realisiert, mit dem mehrere Bits gleichzeitig ausgelesen werden können. Die Antenne arbeitet zwischen 4 − 6GHz und erreicht einen Öffnungswinkel (engl. half power beam width, HPBW) von 15° bei 19dBi Antennengewinn und −10dB SLL. Im Zusammenspiel mit den physikalisch modulierenden RFID Tags konnte mit diesem UWB RA eine Lesereichweite von 1m erzielt werden, was nach meinem Kenntnisstand die größte bisher für ein chiploses frequenzkodiertes (engl. frequency coded, FC) RFID System erreichte Lesereichweite in einer realen Innenraum Umgebung darstellt. Weiter wird eine dual polarisierte RA Antenne mit geringem Kreuzpolarisations Pegel vorgestellt. Es wird vorgeschlagen diese Antenne mit den ko-/kreuzpolarisierten RFID Tags zu verwenden. Als letztes wird eine RA Antenne mit elektronischer Strahlsteuerung eingeführt, die die Stabilität des Lesevorgangs weiter erhöht und eine präzise Ortung der chiplosen RFID Tags ermöglicht. Dazu wird eine Zelle vorgeschlagen, die mit Hilfe einer Varaktordiode in der Lage ist, für einzelne Frequenzen die Phase des reflektierten Signals elektronisch zu steuern. Ein Scanbereich von ±50° kann damit abgedeckt werden. Als dritter Aspekt werden nicht-lineare physikalisch modulierende RFID Tags vorgeschlagen. Hier ist der Kerngedanke, dass der RFID Tag seine ID mit einer anderen Frequenz zurückstrahlt als die mit der er selber angestrahlt wird. Durch dieses nichtlineare Verhalten wird die Umgebungsstrahlung komplett ausgeblendet, die sonst unumgänglichen Kalibrierungsmessungen werden überflüssig, das Problem der Verstimmung durch das RFID Tag Material wird umgangen und die Abdeckung wird erhöht. Die Nicht-Linearität wird durch eine einzige in die Struktur des RFID Tags integrierte Diode erzeugt. Zunächst werden RFID Tags vorgeschlagen, die mit Nichtlinearitäten zweiter Ordnung arbeiten. Für diese Kategorie werden drei unterschiedliche RFID Tags entworfen. Als Erstes ein Einzelton harmonischer RFID Radar Tag. In dieser Klasse strahlt das RFID Lesegerät einige spezifische Grundtöne aus, die schmalbandige Empfangsan-tenne des RFID Tags ist auf einen Grundton abgestimmt, den sie an die Diode weiterleitet. Die hier generierte zweite Harmonische wird von der entsprechend konfigurierten Sendeantenne der RFID Tags zurückgestrahlt. Dabei gilt, je schmaler der Bandbassfilter, desto mehr Frequenzen können zur Kodierung genutzt werden. Um die Codekapazität zu erhöhen werden als nächsten Mehrfrequenzabfragen vorgestellt. Dazu werden am RFID Lesegerät nacheinander, um keine Mischprodukte entstehen zu lassen, vordefinierte Frequenzen durchlaufen. Auf dem RFID Tag können jetzt mehrere ID Bits wieder durch die unterschiedlichen Frequenzen der jeweiligen zweiten Harmonischen erzeugt werden (engl. Notch Position Modulation, NPM). Anschließend werden festdefinierte Frequenzpaare zum Auslesen der ID verwendet. Die Diode mischt beide Frequenzen und antwortet nur auf der Mischfrequenz eines der Frequenzpaare. In einer weiteren Kategorie werden die Intermodulationseigenschaften der dritten Ordnung ausgenutzt, mit dem Vorteil, dass nur ein relativ geringer Frequenzbereich benötigt wird. Hierbei wir der RFID Tag mit zwei benachbarten Frequenzen bestrahlt und die zurückgestrahlte Intermodulationsfrequenz stellt die ID des RFID Tags dar. Schließlich wird die Kodierung über die Phaseninformation vorgestellt. Zusätzlich zur Existenz oder Fehlen eines Peaks oder Notches wird der dazuge- hörige relative Phasenzustand zur Kodierung herangezogen. Alle vorgestellten RFID Tags und ihre Modulation werden an Hand von Harmonische-Balance-Analyse, EM Simulationen und Messungen in einer realen Testumgebung überprüft. Zum Schluss lässt sich sagen, die einzigartigen Eigenschaften, die in der vorliegenden Dissertation betrachtet werden, bringen wesentliche Verbesserungen für den Einsatz von chiplosen RFID Systemen.Recently, the chipless Radio Frequency Identification (RFID) technology has attracted tremendous attention in the market of item identification where the cost is the main concern. However, up to date the technology is at the conceptual level and suffers from a lot of imitations that hinder the technology deployment. The chipless RFID system comprises three major parts which are the reader circuit, the interrogation antennas, and the chipless tags. The contributions of this dissertation are to overcome the challenges that impede the deployment of the chipless RFID system from the perspective of innovating physically modulated tags and developing the reader antenna system. In particular, the system is considered in three novel aspects. The first aspect is the linear physically modulated tags where the tag is interrogated by Ultra Wideband (UWB) signal and the tag inscribed metallic resonators are physically modulating the interrogation frequencies. Therefore, the UWB waveform is modulated in the form of resonant notches, and/or peaks that are inherently embedded in the tag backscattered Radar Cross Section (RCS) frequency response. In this regard, four innovative physically modulated tags are developed aiming at enhancing the coding efficiency, maximizing the coding capacity, conserving the operating frequency range and preserving the tag size. The first tag is based on nested circular ring resonators where each resonator codifies a tag coding notch. Terefore, the tag structure is scalable, printable and compact size. Moreover, a novel encoding methodology is employed to preserve the notch width and position while coding. The second developed tag is a depolarizing one where the polarization isolation between the reader interrogation signal and the tag response is utilized to minimize the environmental clutter reflections. Furthermore, the tag is scalable, printable, and compact size in the credit card format. Thirdly, a novel Notch Width Modulation (NWM) tag is introduced where the tag-ID is not only based on the notch position but also on the notch width. Hence, the notch width configures a further dimension to increase the Degree of Freedom (DoF) for coding and modulation. Therefore, the notch width and position are modulated simultaneously aiming at enhancing the coding efficiency and capacity. Lastly, a novel On Off Notch/Peak (OO-N/P) and Notch/Peak-Position (N/P-P) modulation tag is introduced. The tag basic idea is to exploit both the co-polarized and cross polarized backscattered signals from a tag excited with a linear polarized wave. Consequently, the tag signature is encoded into Notch/Peak (N/P) format in two orthogonal planes. Thus, the Co/Cross-polarizing N/P modulation scheme presents a novel criterion for enhancing the coding efficiency and capacity of the chipless RFID systems. Moreover, the cross-polarized response enhances the tag detection in a realistic environment. The proposed tags and their associated physical modulation schemes are validated using Electro Magnetic (EM) simulations and real-world testbed measurements. In the second aspect, the Reflectarray (RA) antenna is proposed to be utilized in the reader side aiming at increasing the reading range, minimizing the environmental reflections, and acquiring a lot of novel capabilities that can not be provided by the conventional antenna arrays. The spatial feeding RA antenna is easily integrated with the RF circuits, lightweight, conformal geometry, and low cost. Hence, in this concern, three different novel designs are developed. The first design utilizes the Log Periodic Array (LPDA) antenna to feed the developed RA surface. This introduced prototype operates at 5.8GHz and achieves 300MHz bandwidth. Moreover, the RA antenna radiation beam is 4 times narrower than the feeder beam and thus 6dB higher in gain with −10dB Side Lobe Level (SLL). The second developed prototype uses a constant phase center horn antenna to feed the RA surface. Thus, an UWB RA antenna enabling multiple bits accommodation is designed. This antenna operates from 4GHz to 6GHz with 15° Half Power Beam Width (HPBW), 19dBi gain, and −10dB SLL. Furthermore, this developed UWB RA antenna is successfully integrated with the physically modulated tags and a reading range of 1m is achieved. To the best of my knowledge, this is the highest reading range achieved in the Frequency Coded (FC) chipless RFID systems, considering real-world indoor environment and software defined radio reader. After that, dual-polarized RA antenna with low cross-polarization level is presented. This RA antenna is proposed to be utilized with the Co/Cross-polarizing tags. Finally, a successful implementation of an electronic beam steering RA antenna is introduced. This novel beam steering RA antenna system enhances the reading robustness and can precisely locate the chipless tags. In this concern, a novel unit cell that is able to electronically control the reflected phase at different discrete frequencies utilizing a single varactor diode is proposed. Therefore, a scanning range of ±50° is achieved. Moreover, the steered beams are 4 times narrower than the feeder beam and thus 4 times higher in gain. In the third aspect, the nonlinear physically modulated tags are proposed. The core functionality relies on interrogating the tag with a prescribed set and format of frequencies in a time regulated technique while the tag replies with its unique ID at other frequencies. Therefore, the nonlinearity is exploited to completely isolate the environmental clutter reflections, get rid of the necessary reference calibration measurements, overcome the detuning caused by the tagged item materials, and increase the coverage. These objectives are attained by exploiting the nonlinearity generated from a single unbiased diode integrated with the tag structure. The first proposed tag category relies on exploiting the second order nonlinear terms. Therefore, in this regard, three novel tags are introduced. The first class is the single tone harmonic radar tags. In this class, the reader scans the available tags by sending specific fundamental tones. Then, the tag receiving antenna is tuned at only one of these fundamentals which is maximally conveyed to the nonlinear device for generating the corresponding harmonics. Consequently, the tag transmitting antenna is tuned at the second harmonic which is retransmitted back towards the reader representing the tag-ID. Thus, the narrower is the band-pass filter provided by the tag receiving antenna or integrated into it, the more the frequencies that can be utilized for coding. After that, the multi-tone interrogation is proposed to increase the coding capacity. Hence, the tag is interrogated with a prescribed set of fundamentals that are swept over the time to avoid the generation of the mixing products in the reader and tag as well. The tag in turn which is completely planar based on the Coplanar Waveguide (CPW) technology implements a Notch Position Modulation (NPM) scheme in the second harmonics of these fundamental tones. Therefore, the notches that are existing in the second harmonic response symbolize the tag-ID. Afterward, the simultaneous multi-tone interrogation is explored. In this concern, a set of distinct frequency pairs are used to interrogate the nonlinear tags. As a consequence, these tones are mixed through the nonlinear device. Consequently, the tag transmitting antenna figures out only one of these mixed products. The second proposed tag category relies on exploiting the inter-modulation communication principle which exhibits a small frequency span. Therefore, the tag is illuminated by two co-located frequencies and respond at an inter-modulated frequency which is retransmitted by the tag transmitting antenna representing the tag-ID. Finally, the phase encoding capability is proposed. Therefore, not only the existence or the non-existence of a harmonic notch or peak used in coding the tag-ID but also the corresponding relative phase states can be considered. The introduced tags and their associated physical modulation schemes are verified using harmonic balance analysis, EM simulations and realistic testbed measurements. Lastly, the unique features which are considered in the dissertation bring a significant enhancement to the deployment of the chipless RFID system