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This thesis demonstrates the further development of an ultra-wideband (UWB) pulse generator and of an UWB antenna. Custom prototypes of these devices were initially developed for an ongoing research project. The project topic is a compact and portable concealed weapons detection (CWD) radar system to find objects such as firearms, knives, and grenades hidden on persons as they pass by. The system uses the UWB pulse generator as a transmitter, while the UWB antenna radiates the pulse and receives the corresponding backscatter from targets and other objects. Initial device prototypes do not perform adequately according to project specifications. A key specification is of adequate operation over the entire 0.5 GHz to 5 GHz frequency band, where adequate operation is defined distinctly for the antenna and pulse generator. In this work, empirical investigations of both devices are performed using techniques such as simulation, fabrication, and measurement. Through these investigations, the designs of the devices have been incrementally modified. Measured performance data suggest that the research has yielded designs with substantially improved bandwidth as a result. Bandwidth increases from 3.31 GHz to 4.36 GHz (31.7%) for the pulse generator and from 0.46 GHz to 4.98 GHz (983%) for the antenna are demonstrated. Future work is needed to establish the effects of fabrication tolerance, component tolerance, and human error on the variation of the observed device performance. / Thesis / Master of Applied Science (MASc) / This thesis is about the improvement of a radio antenna and a transmitter. These are ultimately intended as components in a system for detecting weapons (such as firearms, knives, etc.) concealed within the clothing or bags of nearby persons. The detection happens by transmitting specific radio signals which interact harmlessly with a person being scanned, and then are received back by the system. This is a form of radio detection and ranging (RADAR). The research on these devices has consisted of computer simulations and real-life measurements. As a result, it appears that the transmitter and radio antenna have been improved to be more suitable for the desired application than they were originally.

Yes / Near field imaging using microwaves in medical applications is of great current interest for its capability and accuracy in identifying features of interest, in comparison with other known screening tools. This paper documents microwave imaging experiments on breast cancer detection, using active antenna tuning to obtain matching over a wide bandwidth. A simple phantom consisting of a plastic container with a low dielectric material emulating fatty tissue and a high dielectric constant object emulating a tumor is scanned between 4 to 8 GHz with a UWB microstrip antenna. Measurements indicate that this prototype microwave sensor is a good candidate for such imaging applications. / Yorkshire Innovation Fund, Research Development Project (RDP)

Gait analysis is the systematic study of human walking. Clinical gait analysis is the process by which quantitative information is collected for the assessment and decision-making of any gait disorder. Although observational gait analysis is the therapist's primary clinical tool for describing the quality of a patient's walking pattern, it can be very unreliable. Modern gait analysis is facilitated through the use of specialized equipment. Currently, accurate gait analysis requires dedicated laboratories with complex settings and highly skilled operators. Wearable locomotion tracking systems are available, but they are not sufficiently accurate for clinical gait analysis. At the same time, wireless healthcare is evolving. Particularly, ultra wideband (UWB) is a promising technology that has the potential for accurate ranging and positioning in dense multi-path environments. Moreover, impulse-radio UWB (IR-UWB) is suitable for low-power and low-cost implementation, which makes it an attractive candidate for wearable, low-cost, and battery-powered health monitoring systems. The goal of this research is to propose and investigate a full-body wireless wearable human locomotion tracking system using UWB radios. Ultimately, the proposed system should be capable of distinguishing between normal and abnormal gait, making it suitable for accurate clinical gait analysis. / Ph. D.

Recently, Radio Frequency Identification (RFID) technology has become commonplace in many applications. It is based on storing and remotely retrieving the data embedded on the tags. The tag structure can be chipped or chipless. In chipped tags, an integrated IC attached to the antenna is biased by an onboard battery or interrogating signal. Compared to barcodes, the chipped tags are expensive because of the existence of the chip. That was why chipless RFID tags are demanded as a cheap candidate for chipped RFID tags and barcodes. As its name expresses, the geometry of the tag acts as both modulator and scatterer. As a modulator, it incorporates data into the received electric field launched from the reader antenna and reflects it back to the receiving antenna. The scattered signal from the tag is captured by the antenna and transferred to the reader for the detection process. By employing the singularity expansion method (SEM) and the characteristic mode theory (CMT), a systematic design process is introduced by which the resonant and radiation characteristics of the tag are monitored in the pole diagram versus structural parameters. The antenna is another component of the system. Taking advantage of ultra-wideband (UWB) technology, it is possible to study the time and frequency domain characteristics of the antenna used in chipless RFID system. A new omni-directional antenna element useful in wideband and UWB systems is presented. Then, a new time-frequency technique, called short-time matrix pencil method (STMPM), is introduced as an efficient approach for analyzing various scattering mechanisms in chipless RFID tags. By studying the performance of STMPM in early-time and late-time responses of the scatterers, the detection process is improved in cases of multiple tags located close to each other. A space-time-frequency algorithm is introduced based on STMPM to detect, identify, and localize multiple multi-bit chipless RFID tags in the reader area. The proposed technique has applications in electromagnetic and acoustic-based detection of targets. / Ph. D.

The communication industry leverages technical advancements in various domains, such as semiconductors, optics, signal processing, and integrated circuits, leading to remarkable evolution over the last decades. This progress paves the way for ever-expanding networks and systems that demand more information capacity, which results in exponential data growth. Unique wireless concepts and technologies are emerging to enable next-generation communication. This dissertation explores the techniques and architectures to realize massive MIMO, extreme bandwidths through channel aggregation, TeraHertz band utilization, and the use of III-V technologies to enhance performance via heterogeneous integration, ultimately maintaining ubiquitous connectivity. The first chapter discusses the various recent research trends in communication technologies: the allocation of millimeter-wave frequencies to benefit from the broad available spectrum, 2D scalability to enhance system performance and overcome link budget requirements, MIMO, and channel aggregation concepts to extend data capacity, heterogeneous integration to exploit benefits of various technologies, transitioning to THz region to improve spectrum efficiencies and diversify applications. The key insight of this dissertation is that we implement distinct system/architecture-level solutions to achieve target data rates for the continuation of the advancements in communication technologies. The first project in this thesis presents a MIMO receiver array that utilizes a simplified single-wire interface for IF/LO signals that overcomes the high-frequency input/output distribution complexity for large-scale systems. Code-domain multiplexing is performed on the single-wire interface to preserve and transfer individual information of all channels. The four-channel receiver prototype that operates at 28GHz and achieves >20dB channel-to-channel isolation is presented. Digital beamforming and MIMO capability of the array have been demonstrated. The later chapter of this dissertation discusses the fundamental limitation of code-domain multiplexing, the trade-off between isolation and interface bandwidth, and explains our novel frequency-domain multiplexing approach. A harmonic rejection mixer has been used to generate the required multiple LO tones to de-multiplex individual channel signals simultaneously. A 60GHz four-element MIMO transmitter prototype is presented, and its functionalities are illus- trated. The prototype achieves >30dB channel-to-channel isolation for an overall bandwidth of 10GHz, supports 64QAM modulated signals, and is capable of performing MIMO beamforming. Next, benefiting from our research experience on FDM and HRM, we proposed a frequency- interleaving architecture for wideband channel aggregated systems. We divided the total IF band- width into four sub-channels and individually up/down-converted them to the baseband, alleviating the requirements of Analog-to-Digital/Digital-to-Analog Converters. HRM is utilized to generate multiple LO frequencies, as in the FDM-based transmitter work. The prototype system comprises two baseband channelizer ICs (TX/RX) and two mm-wave beamformer ICs (TX/RX), where channelizers perform FI aggregation and despread IF signals, and beamformers are responsible for beam steering and tapering. The four-channel transceiver chipset operates at 60GHz, provides >25dB isolation for an overall IF bandwidth of 8GHz, and supports 64QAM modulated signals. The next section of the dissertation presents a wideband sub-THz transceiver phased array system with SWI. We propose a D-band scalable 16-element transceiver system with novel front- end block designs to satisfy link budget requirements and enable high data rates and complex modulation data transfer. The prototype consists of one phased array transmitter and one phased array receiver. Simulated performance shows that the receiver system has ∼34dB gain, -30dBmIP1dB with a minimum 5.4dB NF. While, transmitter achieves ∼34dB gain with a 9dBm OP1dB. The last chapter looks beyond CMOS technology and presents front-end blocks at III-V technologies. Two circulator prototype designs with different architectures are implemented using GaN technology. Better linearity performance is targeted by leveraging heterogeneous integration, using GaN devices for the core and CMOS circuitry for clock generation. In addition, a future direction for THz systems, GaN-assisted beamformer architecture, is presented.

Despite the fact ultra-wideband (UWB) technology has been around for over 30 years, there is a newfound excitement about its potential for communications. With the advantageous qualities of multipath immunity and low power spectral density, researchers are examining fundamental questions about UWB communication systems. In this work, we examine UWB communication systems paying particular attention to transmitter and receiver design. This thesis is specifically focused on a software radio transceiver design for impulse-based UWB with the ability to transmit a raw data rate of 100 Mbps yet encompasses the adaptability of a reconfigurable digital receiver. A 500 ps wide Gaussian pulse is generated at the transmitter utilizing the fast-switching characteristics of a step recovery diode. Pulse modulation is accomplished via several stages of RF switches, filters, and amplifiers on a fully designed printed circuit board specifically manufactured for this project. Critical hardware components at the receiver consist of a bank of ADCs performing parallel sampling and an FPGA employed for data processing. Using a software radio design, various modulation schemes and digital receiver topologies are accommodated along with a vast number of algorithms for acquisition, synchronization, and data demodulation methods. Verification for the design is accomplished through transmitter hardware testing and receiver design simulation. The latter includes bit error rate testing for a variety of modulation schemes and wireless channels using a pilot-based matched filter estimation technique. Ultimately, the transceiver design demonstrates the advantages and challenges of UWB technology while boasting high data rate communication capability and providing the flexibility of a research testbed. / Master of Science

Ultra-wideband (UWB) radio techniques have long promised good contrast and high resolution for imaging human tissue and tumours; however, to date, this promise has not entirely been realised. In recent years, microwave imaging has been recognised as a promising non-ionising and non-invasive alternative screening technology, gaining its applicability to breast cancer by the significant contrast in the dielectric properties at microwave frequencies of normal and malignant tissues. This thesis deals with the development of two novel imaging methods based on UWB microwave signals. First, the mode-matching (MM) Bessel-functions-based algorithm, which enables the identification of the presence and location of significant scatterers inside cylindrically-shaped objects is introduced. Next, with the aim of investigating more general 3D problems, the Huygens principle (HP) based procedure is presented. Using HP to forward propagate the waves removes the need to apply matrix generation/inversion. Moreover, HP method provides better performance when compared to conventional time-domain approaches; specifically, the signal to clutter ratio reaches 8 dB, which matches the best figures that have been published. In addition to their simplicity, the two proposed methodologies permit the capture of a minimum dielectric contrast of 1:2, the extent to which different tissues, or differing conditions of tissues, can be discriminated in the final image. Moreover, UWB allows all the information in the frequency domain to be utilised, by combining information gathered from the individual frequencies to construct a consistent image with a resolution of approximately one quarter of the shortest wavelength in the dielectric medium. The power levels used and the specific absorption rates are well within safety limits, while the bandwidths satisfy the UWB definition of being at least 20% of the centre frequencies. It follows that the methodologies permit the detection and location of significant scatterers inside a volume. Validation of the techniques through both simulations and measurements have been performed and presented, illustrating the effectiveness of the methods.

Near field imaging using microwave in medical applications has gain much attention recently as various researches show its high ability and accuracy in illuminating object comparing to the well-known screening tools such as Magnetic Resonance Imaging (MRI), digital mammography, ultrasound etc. This has encourage and motivate scientists continue to exploit the potential of microwave imaging so that a better and more powerful sensing tools can be developed. This thesis documents the development of antenna design for microwave imaging application such as breast cancer detection. The application is similar to the concept of Ground Penetrating Radar (GPR) but operating at higher frequency band. In these systems a short pulse is transmitted from an antenna to the medium and the backscattered response is investigated for diagnose. In order to accommodate such a short pulse, a very wideband antenna with a minimal internal reflection is required. Printed monopole and planar metal plate antenna is implemented to achieve the necessary operating wide bandwidth. The development of new compact printed planar metal plate ultra wide bandwidth antenna is presented. A generalized parametric study is carried out using two well-known software packages to achieve optimum antenna performance. The Prototype antennas are tested and analysed experimentally, in which a reasonable agreement was achieved with the simulations. The antennas present an excellent relative wide bandwidth of 67% with acceptable range of power gain between 3.5 to 7 dBi. A new compact size air-dielectric microstrip patch-antenna designs proposed for breast cancer detection are presented. The antennas consist of a radiating patch mounted on two vertical plates, fed by coaxial cable. The antennas show a wide bandwidth that were verified by the simulations and also confirmed experimentally. The prototype antennas show excellent performance in terms the input impedance and radiation performance over the target range bandwidth from 4 GHz to 8 GHz. A mono-static model with a homogeneous dielectric box having similar properties to human tissue is used to study the interaction of the antenna with tissue. The numerical results in terms the matching required of new optimised antennas were promising. An experimental setup of sensor array for early-stage breast-cancer detection is developed. The arrangement of two elements separated by short distance that confined equivalent medium of breast tissues were modelled and implemented. The operation performances due to several orientations of the antennas locations were performed to determine the sensitivity limits with and without small size equivalent cancer cells model. In addition, a resistively loaded bow tie antenna, intended for applications in breast cancer detection, is adaptively modified through modelling and genetic optimisation is presented. The required wideband operating characteristic is achieved through manipulating the resistive loading of the antenna structure, the number of wires, and their angular separation within the equivalent wire assembly. The results show an acceptable impedance bandwidth of 100.75 %, with a VSWR < 2, over the interval from 3.3 GHz to 10.0 GHz. Feasibility studies were made on the antenna sensitivity for operation in a tissue equivalent dielectric medium. The simulated and measured results are all in close agreement.

Une communication est impulsive chaque fois que le signal portant des informations est intermittent dans le temps et que la transmission se produit à rafales. Des exemples du concept impulsife sont : les signaux radio impulsifs, c’est-à-dire des signaux très courts dans le temps; les signaux optiques utilisé dans les systèmes de télécommunications; certains signaux acoustiques et, en particulier, les impulsions produites par le système glottale; les signaux électriques modulés en position d’impulsions; une séquence d’événements dans une file d’attente; les trains de potentiels neuronaux dans le système neuronal. Ce paradigme de transmission est différent des communications continues traditionnelles et la compréhension des communications impulsives est donc essentielle. Afin d’affronter le problème des communications impulsives, le cadre de la recherche doit inclure les aspects suivants : la statistique d’interférence qui suit directement la structure des signaux impulsifs; l’interaction du signal impulsif avec le milieu physique; la possibilité pour les communications impulsives de coder l’information dans la structure temporelle. Cette thèse adresse une partie des questions précédentes et trace des lignes indicatives pour de futures recherches. En particulier, nous avons étudié: un système d'accès multiple où les utilisateurs adoptent des signaux avec étalement de spectre par saut temporel (time-hopping spread spectrum) pour communiquer vers un récepteur commun; un système avec un préfiltre à l'émetteur, et plus précisément un transmit matched filter, également connu comme time reversal dans la littérature de systèmes à bande ultra large; un modèle d'interférence pour des signaux impulsifs. / A communication is impulsive whenever the information-bearing signal is burst-like in time. Examples of the impulsive concept are: impulse-radio signals, that is, wireless signals occurring within short intervals of time; optical signals conveyed by photons; speech signals represented by sound pressure variations; pulse-position modulated electrical signals; a sequence of arrival/departure events in a queue; neural spike trains in the brain. Understanding impulsive communications requires to identify what is peculiar to this transmission paradigm, that is, different from traditional continuous communications.In order to address the problem of understanding impulsive vs. non-impulsive communications, the framework of investigation must include the following aspects: the different interference statistics directly following from the impulsive signal structure; the different interaction of the impulsive signal with the physical medium; the actual possibility for impulsive communications of coding information into the time structure, relaxing the implicit assumption made in continuous transmissions that time is a mere support. This thesis partially addresses a few of the above issues, and draws future lines of investigation. In particular, we studied: multiple access channels where each user adopts time-hopping spread-spectrum; systems using a specific prefilter at the transmitter side, namely the transmit matched filter (also known as time reversal), particularly suited for ultrawide bandwidhts; the distribution function of interference for impulsive systems in several different settings.