Sensors based on radio waves are used for inline moisture determination in the sawn wood industry. Placed at the final sorting line such a device can be invaluable, giving the operators real time information on the moisture content of the boards passing through. Information that can then be used to improve process control both upstream and downstream. The equipment must first be trained to correlate radio wave attenuation and phase shift to water conten

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.

L'acronyme anglais RFID « Radio Frequency Identification » désigne en français l'identification par radiofréquence, une technologie qui permet d'identifier et de localiser sans contact des objets ou des personnes grâce à une micro-puce qui dialogue par ondes radio avec un lecteur, sur des distances allant de quelques centimètres à une dizaine de mètres. Déjà présente dans notre quotidien, via les cartes d'accès à certains bâtiments notamment, la RFID est appelée à se développer de manière exponentielle dans les années à venir pour concrétiser à terme le futur Internet des objets.À l'instar de toute innovation technologique, la RFID nécessite un environnement juridique pour pouvoir s'épanouir à la fois économiquement et socialement. C'est pourquoi la présente étude se propose d'exposer les diverses problématiques juridiques afférentes à la RFID. Pour assurer le succès d'une technologie émergente, il est nécessaire que les individus aient confiance en elle, sans quoi le marché ne pourra pas démarrer. Afin de générer cette confiance, la sécurité est primordiale, avant tout d'un point de vue technique mais également sur le plan juridique.L'objectif de cette thèse sera d'étudier le cadre juridique applicable à la technologie RFID, à la fois du point de vue de son contenant, le système, et de son contenu, les données. Quels sont les défis juridiques soulevés par cette technologie ? Existe-t-il des textes applicables à la RFID, et quels sont-ils ? Comment le juriste intègre-t-il cette technologie émergente au cadre juridique existant ? La réflexion est menée afin d'apprécier la nature des rapports entretenus entre la RFID et le droit, et leur éventuelle perfectibilité. / The acronym RFID stands for Radio Frequency Identification, a wireless technology that provides the ability to automatically identify and locate tags attached to objects, as well as the person who is actually carrying them. The technology relies on storing and retrieving data, through radio waves by using devices called RFID tags. Those tags are already prevalent in our everyday lives to grant building access control for example. And this is only the beginning, as RFID technology is expected to be one of the main brick of the Internet of things. Like any other new technology, RFID needs a suitable legal framework to get benefits to both consumers and businesses. This work is thus intended to bring up RFID from a legal perspective. Indeed, one of the new technology key successes lies on the way the consumers will grasp it. When looking for economic profits, it is then essential to focus on public perception and consumer confidence related to this technology. And this would not come along without security concern which represents actually the main challenge to face, most of all from a technical perspective, but also from a legal one.For this reason, the proposed work aims at exposing the legal framework which could be applied both to its container (the RFID system) and its content (the RFID data). It is worth analysing the way the legal practitioner can deal with this technology and all its related issues. Are there any specifics legislations on this subject? And if so, what are they? A critical assessment is undertaken to appreciate the substance of the relationships existing between RFID and law, and potential improvement that come along.

<p>Polarisation, which was first studied in optics, is a fundamental property of all electromagnetic fields. A convenient way to describe the polarisation of two dimensional electromagnetic fields is given by the Stokes parameters. This thesis deals with different aspects of wave polarisation and electromagnetic field measurements. A generalisation of the Stokes parameters to three dimensions is presented. The theory has been used to develop methods and systems for obtaining the polarisation parameters of electromagnetic waves. The methods can be applied for a wide range of electromagnetic fields, measured both on ground and onboard satellites. The applications include, e.g., direction-finding, polarisation analysis, radar, and several examples in the field of wireless communication. Further applications are given in the analysis of satellite data, where a whistler wave is considered. Whistlers are circularly polarised electromagnetic waves propagating in the magnetosphere along the geomagnetic field. Dispersion in the magnetospheric plasma make the whistler frequencies travel at different speeds and the signal takes the form of a chirp. From instantaneous polarisation analysis of the whistler´s magnetic wave field, the normal to the polarisation plane is obtained and found to precess around the geomagnetic field. A statistic analysis of ionospheric stimulated electromagnetic emissions (SEE) is also presented. SEE is generated by injecting a powerful high frequency radio wave into the ionosphere. It is shown that the SEE features have a statistical behaviour indistinguishable from the amplitude and phase distributions of narrow-band Gaussian noise. The results suggests that SEE cannot be explained by simple coherent processes alone. Finally, an expression for the complex Poynting theorem is derived for the general case of anharmonic fields. It is found that the complex Poynting theorem, for real fields and sources, is not a conservation law of the imaginary part of electromagnetic energy.</p>

Polarisation, which was first studied in optics, is a fundamental property of all electromagnetic fields. A convenient way to describe the polarisation of two dimensional electromagnetic fields is given by the Stokes parameters. This thesis deals with different aspects of wave polarisation and electromagnetic field measurements. A generalisation of the Stokes parameters to three dimensions is presented. The theory has been used to develop methods and systems for obtaining the polarisation parameters of electromagnetic waves. The methods can be applied for a wide range of electromagnetic fields, measured both on ground and onboard satellites. The applications include, e.g., direction-finding, polarisation analysis, radar, and several examples in the field of wireless communication. Further applications are given in the analysis of satellite data, where a whistler wave is considered. Whistlers are circularly polarised electromagnetic waves propagating in the magnetosphere along the geomagnetic field. Dispersion in the magnetospheric plasma make the whistler frequencies travel at different speeds and the signal takes the form of a chirp. From instantaneous polarisation analysis of the whistler´s magnetic wave field, the normal to the polarisation plane is obtained and found to precess around the geomagnetic field. A statistic analysis of ionospheric stimulated electromagnetic emissions (SEE) is also presented. SEE is generated by injecting a powerful high frequency radio wave into the ionosphere. It is shown that the SEE features have a statistical behaviour indistinguishable from the amplitude and phase distributions of narrow-band Gaussian noise. The results suggests that SEE cannot be explained by simple coherent processes alone. Finally, an expression for the complex Poynting theorem is derived for the general case of anharmonic fields. It is found that the complex Poynting theorem, for real fields and sources, is not a conservation law of the imaginary part of electromagnetic energy.

Electromagnetic waves can be used to transmit information over long distances and are therefore often employed for communication purposes. The electromagnetic waves are reflected off material objects on their paths and interact with the medium through which they propagate. For instance, the plasma in the ionosphere can refract and even reflect radio waves propagating through it. By increasing the power of radio waves injected into the ionosphere, the waves start to modify the plasma, resulting in the generation of a wide range of nonlinear processes, including turbulence, in particular near the reflection region. By systematically varying the injected radio waves in terms of frequency, power, polarisation, duty cycle, inclination, etc. the ionosphere can be used as an outdoor laboratory for investigating fundamental properties of the near-Earth space environment as well as of plasma turbulence. In such ionospheric modification experiments, it has been discovered that the irradiation of the ionosphere by powerful radio waves leads to the formation of plasma density structures and to the emission of secondary electromagnetic radiation, a phenomenon known as stimulated electromagnetic emission. These processes are highly repeatable and have enabled systematic investigations of the nonlinear properties of the ionospheric plasma. In this thesis we investigate features of the plasma density structures and the secondary electromagnetic radiation. In a theoretical study we analyse a certain aspect of the formation of the plasma structures. The transient dynamics of the secondary radiation is investigated experimentally in a series of papers, focussing on the initial stage as well as on the decay. In one of the papers we use the transient dynamics of the secondary radiation to reveal the intimate relation between certain features of the radiation and structures of certain scales. Further, we present measurements of unprecedentedly strong secondary radiation, attributed to stimulated Brillouin scattering, and report measurements of the secondary radiation using a novel technique imposed on the transmitted radio waves.

The objective of the proposed research is to develop simplified reconfigurable transmission systems with frequency multipliers for the transmission of complex modulated signals. Because they rely on nonlinear properties, frequency multiplier-based transmission systems require proper linearization techniques and accurate modeling of the signal transfer function. To accomplish these two goals, the author has developed techniques to model and linearize frequency multipliers and to digitize feedback signals for nonlinear characterization. First, adaptive predistortion techniques and zonal transfer theories have been developed for modeling and linearization. The predistortion system has been verified by applying an IS-95B signal to various frequency multipliers built by the author. Second, because the output signals at higher harmonic zones occupy wider frequency bandwidths than the signal in the fundamental zone does and thus make it harder to use traditional sampling techniques, a simplified but effective method called the sub-Nyquist sampling rate was developed and verified. Third, two methods for reconfigurable transmitters using frequency multipliers in conjunction with digital predistortion linearizers were developed. Both methods make it possible to transmit complex signals via frequency multipliers by using dual-band transmission systems that incorporate frequency multipliers that are based on linearization techniques. One of these methods uses a circuit topology that can be switched between a fundamental-mode in-phase combined amplifier and a push-push frequency doubler using input phasing. The second suggested method uses a fundamental-frequency power amplifier followed by a varactor multiplier that can be bypassed with an RF switch. This work will contribute to the development of low-cost and size-effective reconfigurable transmission systems because it requires fewer transmitting components and needs less sampling of the feedback networks.

In ground based high frequency (HF) radio pumping experiments, absorption of ordinary (O) mode pump waves energises the ionospheric plasma, producing optical emissions and other effects. Pump-induced or natural kilometre-scale field-aligned density depletions are believed to play a role in self-focussing phenomena such as the magnetic zenith (MZ) effect, i.e., the increased plasma response observed in the direction of Earth's magnetic field. Using ray tracing, we study the propagation of ordinary (O) mode HF radio waves in an ionosphere modified by density depletions, with special attention to transmission through the radio window (RW), where O mode waves convert into the extraordinary (X, or Z) mode. The depletions are shown to shift the position of the RW, or to introduce RWs at new locations. In a simplified model neglecting absorption, we estimate the wave electric field strength perpendicular to the magnetic field at altitudes normally inaccessible. This field could excite upper hybrid waves on small scale density perturbations. We also show how transmission and focussing combine to give stronger fields in some directions, notably at angles close to the MZ, with possible implications for the MZ effect. In a separate study, we consider electromagnetic (e-m) beams with helical wavefronts (i.e., twisted beams), which are associated with orbital angular momentum (OAM). By applying geometrical optics to each plane wave component of a twisted nonparaxial e-m Bessel beam, we calculate analytically the shift of the beam's centre of gravity during propagation perpendicularly and obliquely to a weak refractive index gradient in an isotropic medium. In addition to the so-called Hall shifts expected from paraxial theory, the nonparaxial treatment reveals new shifts in both the transverse and lateral directions. In some situations, the new shifts should be significant also for nearly paraxial beams.

Radio Frequency Identification (RFID) technology is a ethod of identifying unique items using radio waves that communicate between RFID tags and readers without line-of-sight readability. RFID technology provides great potential in many industries and a wide spectrum of possible uses. Areas of application include person identification, logistics, pharmaceutical, access control, security guard monitoring and asset management. One of the areas where RFID is being used and where it promises excellent results is the retail industry. While RFID systems have the potential to revolutionise the way products and goods are tracked and traced in the retail supply chain, barriers to its widespread adoption exist: for example; technical constraints, return on investment constraints, a lack of awareness and education and as well as privacy and security issues. The research aims to identify the barriers to the adoption of RFID and to investigate the perceptions of RFID held by members of the retail sector in South Africa (SA). Current research and available literature are used to identify RFID adoption barriers and a conceptual framework on this subject is proposed, which is then verified by SA retailers’ perceptions, established by means of a survey. Initial barriers to widespread adoption include a shortage in skills, a lack of standards, high costs associated with RFID devices, the difficulty of integrating with current legacy systems, and a lack of familiarity with the system. Finally, an enhanced framework is proposed, describing RFID adoption barriers within the South African retail sector. In summary, the framework is an outline of the barriers impacting RFID adoption in the SA retail sector that need to be considered and addressed. The framework identifies six categories of RFID adoption barriers, with each category containing two or more barriers relating to that particular category. These categories are Technological, Cost and return on investment, Privacy and security, Implementation, Organisational factors and People.

The ionosphere is an important factor in high frequency (HF) radio propagation providing an opportunity to study ionospheric variability as well as the space weather conditions under which HF communication can take place. This thesis presents the validation of HF propagation conditions for the Ionospheric Communication Enhanced Profile Analysis and Circuit (ICEPAC) and Advanced Stand Alone Prediction System (ASAPS) models over Africa by comparing predictions with the measured data obtained from the International Beacon Project (IBP). Since these models were not developed using information on the African region, a more accurate HF propagation prediction tool is required. Two IBP transmitter stations are considered, Ruaraka, Kenya (1.24°S, 36.88°E) and Pretoria, South Africa (25.45°S, 28.10°E) with one beacon receiver station located in Hermanus, South Africa (34.27°S, 19.l2°E). The potential of these models in terms of HF propagation conditions is illustrated. An attempt to draw conclusions for future improvement of the models is also presented. Results show a low prediction accuracy for both ICEPAC and ASAPS models, although ICEPAC provided more accurate predictions for daily HF propagation conditions. This thesis suggests that the development of a new HF propagation prediction tool for the African region or the modification of one of the existing models to accommodate the African region, taking into account the importance of the African ionospheric region, should be considered as an option to ensure more accurate HF Propagation predictions over this region.