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The Enactment of the Authentic Original: Conservation-restoration of kalkmålningar in Swedish curches around 1850–1980
No full textIn Sweden, there are more than a thousand completely or partially preserved medieval churches, with many containing kalkmålningar (mural paintings), dating from between the twelfth and seventeenth centuries. This thesis deals with the enactments and re-enactments that formed the revival of these paintings, particularly the conservation-restoration work carried out between 1850–1980, including contemporaneous, decorative, and monumental paintings that were created in relation to this revival. The thesis further investigates how kalkmålningar became embedded within Sweden’s listed cultural heritage. Following the enactments, thought collectives of the period are revealed, shedding light on the relation between these paintings and the establishment of theories and practices within the emergent field of conservation-restoration. Through an eclectic methodology–including analysis of written sources, and investigations of the paintings in-situ, partly grounded on inspiration from actor-network theory (ANT), discursive analysis, posthumanism, and object-oriented ontology (OOO)–the thesis asks what agency these paintings have. How can we understand conservation-restoration as a hybrid practice that encompasses a more-than-human perspective, challenging the modern dichotomy between nature and culture? The thesis is divided into three parts. The first part gives an introduction to the thesis, theory, and method, including an analysis of the emergence of conservation-restoration in relation to the modern “thought figure” of the “authentic original”. It gives an introduction to the topic of kalkmålningar in Sweden, and an analysis of the network that enacted them and their collective values. The second part forms a historical analysis and description of the enactments of kalkmålningar between 1850–1980, identifying three periods of different conservation-restoration principles: stylistic restoration, original conservation-restoration, and precautionary conservation-restoration. The third part discusses the enactments that informed the revival of kalkmålningar, and draws conclusions concerning the ontology of conservation and paintings. This part further identifies and discusses particular traditions of Swedish restoration, such as the principles of Sigurd Curman, the precautionary attitude, the pursuit of a lively harmonic church room, the prevalence of handicraft conservation-restoration, as well as the restrictive attitude towards retouching that emerged in the 1960s, and the lack of an institute dedicated to technical studies of art. The thesis concludes with an epilogue, in which three contemporary conservation-restoration tendencies are finally discussed, influenced by a changing perception regarding ethics, sustainability, and the authentic original.I Sverige finns mer än tusen helt eller delvis bevarade medeltida kyrkor, varav många har rester av kalkmålningar från 1100-talet till 1600-talet. Den här avhandlingen behandlar hur dessa kalkmålningar framställdes och återupprättades genom konserverings- och restaureringsåtgärder omkring 1850–1980, inklusive de dekorativa och monumentala muralmålningar som tillkom i relation till kalkmålningarna. Avhandlingen undersöker också hur kalkmålningarna blev en del av det skyddade kulturarvet. Genom att följa hur målningarna framställdes synliggörs de ”tankekollektiv” som ingick i processen och den parallella etableringen av konservering som disciplin. Genom en kombination av metoder – som innefattar såväl analys av skriftligt källmaterial som undersökning av målningarna in situ, delvis grundad på inspiration från aktör-nätverksteori (ANT), diskursanalys, posthumanism och objektorienterad ontologi (OOO) – ställer avhandlingen frågan om målningarnas agens. Hur kan vi förstå konservering och restaurering som en hybrid praktik, som innefattar meränmänskliga perspektiv och utmanar den moderna dikotomin mellan natur och kultur? Avhandlingen är disponerad i tre delar. Den första delen, inledningen, introducerar avhandlingens syfte, teori och metod, och kompletteras av ett avsnitt om framväxten av konserveringen och dess förhållande till tankefiguren om det autentiska originalet. Vidare introduceras kalkmålningarna i Sverige och nätverket som framställde dem samt olika värdegemenskaper. Den andra delen utgör en historisk analys och beskrivning av hur kalkmålningarna framställdes omkring 1850–1980, disponerad utifrån tre perioder med olika, identifierade konserveringsprinciper: stilrestaureringen, originalkonserveringen och försiktighetskonserveringen. Den tredje delen diskuterar avhandlingens resultat genom att dra slutsatser om konserveringens och målningarnas ontologi och om kalkmålningarnas huvudsakliga framställningssätt. Vidare identifieras och diskuteras några svenska särdrag, däribland Sigurd Curmans principer, strävandet efter återhållsamhet och ett levande harmoniskt kyrkorum, betoningen av hantverksmässig konservering och den restriktiva inställningen till retuschering som växte fram under 1960-talet, samt avsaknaden av ett institut för konstteknologi. Avhandlingen avslutas med en epilog, där tre samtida konserveringstendenser diskuteras, påverkade av en ny syn på etik och hållbarhet, samt på det autentiska originalet.QC 20251218</p
Foundations of Computation Via Digital Communications
No full textThe explosive growth of distributed data generation — spanning data centers, sensor networks, massive IoT, and edge learning places an unsustainable burden on modern infrastructure, where the energy and latency costs of moving raw data often outstrip those of processing it. While analog over-the-air computation (OAC) promises a solution by exploiting the natural superposition of wireless waveforms to aggregate data in-channel, it remains fragile against noise and fundamentally incompatible with the ubiquitous digital hardware that powers all modern communication systems. This thesis introduces a digital-native framework that unifies communication and computation at the physical layer. Rather than treating channel interference as an obstacle, we engineer the geometry of digital constellations so that the superposition of signals directly yields the desired function value. This paradigm shift transforms the communication link from a passive data pipe into an active computational engine, applicable to any multiple-access channel—whether wired or wireless—without requiring the decoding of individual inputs. We generalize this framework along three axes to ensure scalability and reliability across diverse network environments. First, we develop noise-aware constellation designs that optimize inter-symbol geometry for non-Gaussian and heavy-tailed interference, ensuring robustness beyond standard Euclidean metrics. Second, we introduce a sampling-based reduction strategy that leverages the symmetry of aggregation functions to cut design complexity by orders of magnitude, enabling deployment in massive-scale networks. Third, we extend the framework to vector-valued computation, utilizing spatial degrees of freedom to perform complex, multi-dimensional aggregations in a single transmission shot without relying on perfect channel state information. Finally, to bridge the gap to immediate deployment, we present a closed-form algebraic coding scheme for exact summation. The proposed solution integrates seamlessly with standard quadrature amplitude modulation, eliminating the need for complex optimization and offering a plug-and-play solution for digital aggregation. We validate these contributions through the lens of Federated Edge Learning, demonstrating that computation-by-communication is not only feasible using standard digital protocols but significantly outperforms traditional orthogonal transmission. Collectively, these works prove that computation-by-communication is not only feasible on digitally modulated signals but superior to analog alternatives, paving the way for the next generation of compute-aware networks, enabling energy efficient, scalable, and robust intelligence across any digital infrastructure.QC 20251127</p
Cutting peaks and costs : Techno-economic design guidelines for solar PVT and GSHP in land-constrained multi-family buildings
No full textThis study conducts a detailed techno-economic analysis of photovoltaic-thermal (PVT) collectors integrated with ground-source heat pumps (GSHPs) for land-constrained multi-family buildings in cold climates. Using dynamic TRNSYS simulations, the system is designed around an undersized borehole field and incorporates realistic electricity pricing models, including dynamic spot prices and capacity-based tariffs, and peak demand considerations. A stepwise analysis evaluates five PVT absorber types, array sizes, layouts, and control strategies. The most cost-effective design combines 60 m2 of unglazed finned collectors, pre-borehole layout, and 80 l/h-m2 fixed flow, achieving a seasonal performance factor above 2.7 and a minimum total life-cycle cost (TLCC) of €451 k€. Among all design variables, array size has the greatest impact on system performance and cost, with flow rate being the next most critical factor. Relative to a stand-alone GSHP, the hybrid system lowers peak electric load by 10 % and reduces total life-cycle cost by 4–23 % when benchmarked against alternative heating configurations including district heating, air-source heat pump, and PV-assisted GSHP. Scenario analyses show that electricity pricing structure and volatility significantly influence optimal collector sizing, with higher electricity prices favoring larger PVT array sizes. The results provide actionable design guidelines for researchers and practitioners seeking to improve performance and cost-effectiveness of heat pump systems, and to support their broader deployment in space- and grid-constrained urban environments.QC 20251217</p
Design procedure for estimating the vertical response of end-bearing piles from free field vibrations produced by a nearby surface load
No full textThis paper investigates the vertical response of end-bearing piles in a homogeneous isotropic linear elastic soil on a rigid bedrock subjected to a vertical harmonic point load at the soil’s surface. A numerical model is used to compute vibration responses. A novel system of dimensionless parameters is established to bring insight into the influence of the relationships between soil and pile properties on the dynamic pile–soil interaction and to allow for general conclusions to be drawn. The results show the conditions under which the relationship between the axial stiffness of the pile and the stiffness of the soil has a significant influence on the end-bearing pile response. Different pile group configurations are considered where the vertical response is found to be bounded by the single pile response, justifying its use as a conservative estimate for the group response. Finally, an expression including only two dimensionless parameters, the pile slenderness ratio and the pile–soil stiffness ratio, is proposed for calculating an estimation of the vertical response of an end-bearing pile from the free field vibrations.QC 20250203</p
The impact of tube voltage on the erosion of rotating x‐ray anodes
No full textBackground The permitted input power density of rotating anode x-ray sources is limited by the performance of available target materials. The commonly used simplified formulas for the focal spot surface temperature ignore the tube voltage despite its variation in clinical practice. Improved modeling of electron transport and target erosion, as proposed in this work, improves the prediction of x-ray output degradation by target erosion, the absolute x-ray dose output and the quality of diagnostic imaging and orthovolt cancer therapy for a wide range of technique factors. Purpose Improved modeling of electronic power absorption to include volume effects and surface erosion, to improve the understanding of x-ray output degradation, enhance the reliability of x-ray tubes, and safely widen their fields of use. Methods We combine Monte Carlo electron transport simulations, coupled thermoelasticity finite element modelling, erosion-induced surface granularity, and the temperature dependence of thermophysical and thermomechanical target properties. A semi-empirical thermomechanical criterion is proposed to predict the target erosion. We simulate the absorbed electronic power of an eroded tungsten-rhenium target, mimicked by a flat target topped with a monolayer of spheres, and compare with a pristine target. Results The absorbed electronic power and with it the conversion efficiency varies with tube voltage and the state of erosion. With reference to 80 kV (100%), the absorption of a severely eroded relative to a pristine target is 105% (30 kV), 99% (100 kV), 97% (120 kV), 96% (150 kV), 93% (200 kV), 87% (250 kV), and 79% (300 kV). We show that, although the simplistic Müller–Oosterkamp model of surface heating underestimates the benefit of higher tube voltages relative to operation at 80 kV, the error is limited to below −6% for 30 kV (reduction advised) and +13% for 300 kV (input power increase permitted). Conclusions Correcting the x-ray conversion efficiency of eroded target material, that is typically not accessible by measuring the tube current, may imply corrections to existing x-ray dose calculations. The relative increase of the allowable anode input power of rotating anode x-ray tubes with increasing tube voltage is substantially smaller than predicted by volume heating models that only rely on the focal spot surface temperature. The widely used voltage agnostic Müller–Oosterkamp formalism fails to predict the tube voltage dependency of the surface temperature of rotating anode targets, ignores the temperature dependency of the thermal diffusivity of tungsten-rhenium, and the granularity of the material. Nevertheless, we show theoretically why, backed by experience, the practical use of the Müller–Oosterkamp formalism is justified in medical imaging and provides a basis for comparison with new microparticle based targets. The reason for this surprising finding is that voltage dependent material erosion must be primarily considered as a precursor of thermal runaway effects.QC 20250203</p
The effect of eccentric arm cycling on muscle damage and injury‐related biomarkers
No full textPurpose: There is a scarcity of information regarding the effect of upper-body eccentric exercise on biomarkers of muscle damage. This study sought to investigate the effect of eccentric arm cycling on muscle damage [exercise-induced muscle damage (EIMD)]. Method: Ten subjects performed a 15 min eccentric arm cycling protocol (cadence 49 ± 7 rpm, power absorbed 248 ± 34 W). Maximal voluntary contraction (MVC) of the elbow flexors was evaluated at rest and at 5 min, 24 h, and 48 h post-exercise. In addition, blood samples were drawn at rest and thereafter at 30 min, 24 h, and 48 h intervals after exercise for quantification of creatine kinase (CK), myoglobin, lactate dehydrogenase (LDH) and endothelin (ET-1) concentrations. Delayed onset muscle soreness (DOMS) was assessed using a category ratio scale (0-10). Results: Myoglobin was increased from baseline at 30 min post-exercise (+114%, 46.08 ± 22.17 µg/L, p = 0.018). Individual peak values were higher than baseline values for CK (+72.8%, 204 ± 138 U/L, p = 0.046) and LDH (+17%, 3.3 ± 0.88 nmole/min/mL, p = 0.017), but not for ET-1 (+9%, 1.4 ± 0.48 pg/mL, p = 0.45). DOMS was reported at 24 h (median 4) and 48 h (median 4) post-exercise and MVC of the elbow flexors were reduced from baseline (216 ± 44 N) at 5 min (-34%, 147 ± 61 N, p < 0.001), 24 h (-17%, 181 ± 56 N, p = 0.005) and 48 h (-9%, 191 ± 54 N, p = 0.003). Conclusion: Eccentric arm cycling incites EIMD with reduced MVC and elevation of myoglobin, CK and LDH.QC 20241030</p
3D micromechanical interaction of thin-film retained austenite and lath martensite by computational plasticity
No full textTo exploit the full potential of advanced high-strength steels (AHSS), a more in-depth understanding of the complex micromechanical interaction of thin-film retained austenite (RA) and lath martensite is indispensable. Inspired by the medium-Mn steel microstructure, a three-dimensional micromechanical modeling approach is therefore proposed in the present work, embedding the thin RA films explicitly into the hierarchical lath martensite structure. This enables systematic studies of the effect of RA film thickness and volume fraction on the local stresses and strains as well as their partitioning within the microstructure. The investigations reveal that with shrinking RA volume fraction, both stress and especially strain heterogeneity in the thin-film RA intensifies. In the martensite blocks, stress and strain heterogeneity also intensifies, although stresses are generally more heterogeneously, and strains much more homogeneously, distributed than in RA. The results underline the key role of RA with thin-film morphology for further optimizing AHSS microstructures.QC 20241119</p
Ground-borne vibration in end-bearing pile foundations : Numerical analyses and full-scale field tests
No full textGround-borne vibration originating from roads or railways is a growing concern in the design of buildings in urban areas. For soft cohesive soils, which are particularly susceptible to ground-borne vibration, pile foundations are often used. In shallow formations of soft soil on till and bedrock, which are conditions encountered in densely populated areas in Sweden, the piles are designed as end-bearing to transfer loads to the bedrock. The transmission of vibrations to a building is governed by the interaction between the soil and the foundation. It is therefore essential that the dynamic interaction between the foundation and the soil is taken into account when predicting vibrations in buildings at a design stage. This thesis aims to increase the understanding of ground-borne vibration transmission to end-bearing pile foundations and investigate how it can be taken into account in vibration assessment for buildings yet to be constructed. The problem is addressed through experiments and numerical simulations. A set of full-scale field tests are performed at a site with clay on till and bedrock to validate model predictions. Vibration measurements are performed in three stages of construction of a pile foundation: (1) at the free ground surface, (2) on the top of four end-bearing concrete piles and (3) on the concrete pile cap joining the piles together. Numerical models are implemented to investigate the influence of pile and soil parameters. The results are subsequently used to develop a simple approximation factor that can be used for estimating the foundation response from vibrations at the ground surface. The main scientific contributions of this work is the experimental validation of models or predicting ground-borne vibrations in an end-bearing pile foundation and an investigation of the influence of pile and soil properties on dynamic pile-soil interaction. The results show that the vertical vibration level of piles is considerably affected by the fixation of the pile tip and the relationship between the pile axial stiffness and the stiffness of the soil. It is found that, in contrast to floating piles, the vertical response of end-bearing piles subjected to an incident wave field can be significantly affected by pile-soil-pile interaction. The field tests show that, if the dynamic properties of the soil can be accurately determined, a numerical model can predict the dynamic vibration response of the pile foundation with reasonable accuracy. This provides confidence in the results obtained from numerical models, motivating their use for vibration assessment.Omgivningsvibrationer från tåg och biltrafik är ett växande problem vid dimensionering av byggnader i stadsmiljö. I lösa kohesionsjordar, som är särskilt känsliga för sådana vibrationer, används ofta pålar vid grundläggning. Vid jordförhållanden med relativt grunda formationer av lös jord på morän och berg, vilket är vanligt förekommande i tätbefolkade områden i Sverige, används ofta spetsburna pålar. Transmissionen av vibrationer från jorden till en byggnad beror på interaktionen mellan jorden och byggnadens grundläggning. Det är därför viktigt att ta hänsyn till den dynamiska interaktionen mellan jord och grundläggning då man avser förutsäga vibrationer i en byggnad i dimensioneringssyfte. Syftet med denna avhandling är att öka kunskapen kring transmissionen av markburna vibrationer till spetsburna pålfundament samt att undersöka hur hänsyn kan tas till dess inverkan i vibrationsutredningar. Frågeställningen adresseras genom både experiment och numeriska analyser. Fältförsök i full skala har utförts på en plats med lerjord på morän och berg för att validera numeriska prediktionsmodeller. Vibrations mätningar har utförts vid tre olika skeden vid installation av ett pålfundament: (1) på den fria markytan, (2) på fyra spetsburna betongpålar och (3) på pålfundamentet som sammanfogar pålarna vid markytan. Numeriska modeller har använts för att undersöka inverkan av parametrar för pålarna och jorden. Resultaten har därefter använts för att utveckla en approximativ reduktionsfaktor som appliceras på uppmätta vibrationer på markytan för att estimera vibrationer av spetsburna pålar. Avhandlingen har resulterat i en validering av numeriska modellers använding för att förutsäga markburna vibrationer i spetsburna pålfundament samt en undersökning av hur pålarnas och jordens egenskaper påverkar den dynamiska interaktionen mellan spetsburna pålar och jord. Resultaten visar att överföringen av vertikala vibrationer från jorden till pålarna påverkas av förhållandet mellan jordens styvhet och pålens axialstyvhet. Resultaten visar även att interaktioner mellan pålar i en grupp påverkar den vertikala responsen orsakad av en dynamisk last på markytan. Fältförsöken visar att om jordens dynamiska egenskaper kan bestämmas med noggrannhet, ger prediktioner från numeriska modeller representativa resultat. Detta ökar tillförlitligheten till resultat erhållna från sådana numeriska modeller vilket motiverar deras användning vid vibrationsutredningar.QC241217</p
Signal Processing and Antenna Design for Sub-Terahertz Radar Using Frequency : Diverse and Scanning Notch-Beam Antennas
No full textThis thesis explores the design, fabrication, characterization, and performance of frequency-diverse antennas and frequency-scanning notch-beam antennas for high-resolution radar detection and imaging at sub-THz frequencies ranging from 220 to 330 GHz. Utilizing cutting-edge silicon micromachining techniques, the body of work presents innovative solutions that address the challenges of high-resolution radar imaging, focusing on improving imaging performance, reducing hardware complexity, and enhancing signal processing techniques. At the heart of this research is analyzing, characterizing, and evaluating a minimalistic beam-shape switching frequency-scanning notch and broad-beam radar systems. A two-antenna system was designed to switch between broad and notch beam patterns, improving imaging resolution and hardware efficiency. The system's ability to operate with fewer components while maintaining high performance was further augmented through advanced signal processing algorithms like TwIST and MUSIC, which offered superior image reconstruction in noisy scenarios. A key aspect of this research was the experimental validation of the scanning notch antenna, which demonstrated its capability for sub-THz imaging. This work evaluated various algorithms, including FISTA, MUSIC, and matched filter methods, highlighting MUSIC's limitations when multiple targets were present. To overcome the challenge of multi-target scenario failure, a novel adaptive IFFT range-gating method was introduced, which markedly enhanced the radar’s ability to distinguish closely spaced targets by separating the return signals more effectively. Further advancing in sub-THz imaging systems, we explored designing and fabricating a Mills-cross frequency-diverse antenna using slot radiators and a direct waveguide feed network. This configuration allows for efficient radiation pattern diversity over the operating bandwidth, contributing to enhanced imaging resolution without complex mechanical scanning or phase shifters. Following this, we developed a more advanced wideband frequency-diverse antenna for 220 to 330 GHz, featuring an array of silicon-micromachined cross-slot radiators. The frequency-diverse antenna using a cross-slot is incorporated with direct and distributed feed networks. This configuration, which utilizes cross-slot radiators and a distributed feed network, significantly improved radiation pattern diversity and imaging resolution. The performance of these frequency-diverse antennas was evaluated using advanced imaging algorithms, with FISTA and CoSaMP emerging as the preferred algorithms for efficient, high-resolution image reconstruction under various noise conditions. These antennas are designed for short-range, high-resolution imaging and eliminate the need for phase shifters or mechanical scanning, achieving diverse radiation patterns across a broad frequency range. Finally, this work culminated in a detailed investigation of imaging performance using these frequency-diverse antennas, where the comparison of direct and distributed feed networks provided key insights into optimizing feed designs for enhanced imaging quality and spatial resolution. Furthermore, we investigated the influence of sparse data collection on imaging performance, considering sparsity in three major areas: 1) when the imaging antenna array is sparsely populated, 2) when sparse frequency sampling is applied across the total available bandwidth, and 3) when the bandwidth is divided among multiple transmitters, each operating over a partial bandwidth, while the receiver utilizes the full bandwidth. These scenarios provided a comprehensive understanding of how sparsity affects overall imaging performance and resolution, enabling more efficient data acquisition without compromising image quality. This thesis substantially contributes to advancing sub-THz radar detection and computational imaging. By integrating innovative antenna designs, adaptive signal processing techniques, and advanced fabrication methods, this research presents a comprehensive solution for achieving high-resolution radar imaging with minimal hardware complexity, paving the way for practical applications in security, medical diagnostics, and structural monitoring.Denna avhandling utforskar design, tillverkning, karakterisering och prestanda hos frekvensdiverse antenner och frekvensskannande notchstråleantenner för högupplöst radardetektion och avbildning vid sub-THz-frekvenser i intervallet 220 till 330 GHz. Genom att använda banbrytande kiselmikromaskineringstekniker presenterar arbetet innovativa lösningar som adresserar utmaningar inom högupplöst radaravbildning, med fokus på att förbättra avbildningsprestanda, minska hårdvarukomplexiteten och stärka signalbehandlingstekniker. Kärnan i denna forskning är att analysera, karakterisera och utvärdera minimalistiska system med strålformsväxling i frekvensskannande notch- och bredstråleradarsystem. Ett system med två antenner designades för att växla mellan breda och smala strålmönster, vilket förbättrade avbildningsupplösning och hårdvarueffektivitet. Systemets förmåga att arbeta med färre komponenter samtidigt som hög prestanda bibehålls, förstärktes ytterligare genom avancerade signalbehandlingsalgoritmer som TwIST och MUSIC, vilka erbjöd överlägsen bildrekonstruktion i bullriga miljöer. En viktig aspekt av denna forskning var experimentell validering av den skannande notch-antennen, som visade sin kapacitet för sub-THz-avbildning. Arbetet utvärderade olika algoritmer, inklusive FISTA, MUSIC och matched filter-metoder, och framhöll MUSICbegränsningar när flera mål var närvarande. För att övervinna utmaningen i scenarion med flera mål introducerades en ny adaptiv IFFT-range-gating-metod, som avsevärt förbättrade radarens förmåga att särskilja tätt placerade mål genom att effektivare separera de mottagna signalerna. Vidareutveckling inom sub-THz-avbildningssystem utforskades genom design och tillverkning av en Mills-cross frekvensdivers antenn med slot-radiatorer och en direktvågledarförsörjningsnät. Denna konfiguration möjliggör effektiv diversitet i strålningsmönster över arbetsbandbredden, vilket bidrar till förbättrad avbildningsupplösning utan komplex mekanisk skanning eller fasskiftare. Därefter utvecklade vi en mer avancerad bredbands frekvensdivers antenn för 220 till 330 GHz, med en array av kiselmikromaskinerade korsslitsradiatorer. Den frekvensdiversa antennen med korsslits kombineras med direkt och distribuerat matningsnätverk. Denna konfiguration, som använder korsslitsradiatorer och ett distribuerat matningsnätverk, förbättrade avsevärt strålningsmönsterdiversiteten och avbildningsupplösningen. Prestandan hos dessa frekvensdiverse antenner utvärderades med avancerade avbildningsalgoritmer, där FISTA och CoSaMP visade sig vara de föredragna algoritmerna för effektiv, högupplöst bildrekonstruktion under olika brusförhållanden. Dessa antenner är utformade för kortdistans och högupplöst avbildning och eliminerar behovet av fasskiftare eller mekanisk skanning, vilket uppnår olika strålningsmönster över ett brett frekvensområde. Slutligen resulterade detta arbete i en detaljerad undersökning av avbildningsprestanda med dessa frekvensdiverse antenner, där jämförelsen av direkt och distribuerade matningsnätverk gav viktiga insikter för att optimera matningsdesigner för förbättrad bildkvalitet och rumslig upplösning. Dessutom undersökte vi inverkan av gles datainsamling på avbildningsprestanda, med hänsyn till gleshet i tre huvudsakliga områden: 1) när antennarrayen för avbildning är glesbefolkad, 2) när gles frekvenssampling appliceras över den tillgängliga bandbredden, och 3) när bandbredden delas mellan flera sändare, var och en som arbetar över en del av bandbredden, medan mottagaren använder hela bandbredden. Dessa scenarier gav en omfattande förståelse för hur gleshet påverkar den övergripande avbildningsprestandan och upplösningen, vilket möjliggör effektivare datainsamling utan att kompromissa med bildkvaliteten. Denna avhandling bidrar avsevärt till att driva fram sub-THz radardetektion och datorbaserad avbildning. Genom att integrera innovativa antenndesigner, adaptiva signalbehandlingstekniker och avancerade tillverkningsmetoder presenterar denna forskning en heltäckande lösning för att uppnå högupplöst radaravbildning med minimal hårdvarukomplexitet, vilket banar väg för praktiska tillämpningar inom säkerhet, medicinsk diagnostik och strukturell övervakning.QC 20241218</p