<p>Multiplications occur frequently in digital signal processing systems, communication systems, and other application specific integrated circuits. Multipliers, being relatively complex units, are deciding factors to the overall speed, area, and power consumption of digital computers. The diversity of application areas for multipliers and the ubiquity of multiplication in digital systems exhibit a variety of requirements for speed, area, power consumption, and other specifications. Traditionally, speed, area, and hardware resources have been the major design factors and concerns in digital design. However, the design paradigm shift over the past decade has entered dynamic power and static power into play as well.</p><p>In many situations, the overall performance of a system is decided by the speed of its multiplier. In this thesis, parallel multipliers are addressed because of their speed superiority. Parallel multipliers are combinational circuits and can be subject to any standard combinational logic optimization. However, the complex structure of the multipliers imposes a number of difficulties for the electronic design automation (EDA) tools, as they simply cannot consider the multipliers as a whole; i.e., EDA tools have to limit the optimizations to a small portion of the circuit and perform logic optimizations. On the other hand, multipliers are arithmetic circuits and considering arithmetic relations in the structure of multipliers can be extremely useful and can result in better optimization results. The different structures obtained using the different arithmetically equivalent solutions, have the same functionality but exhibit different temporal and physical behavior. The arithmetic equivalencies are used earlier mainly to optimize for area, speed and hardware resources.</p><p>In this thesis a design methodology is proposed for reducing dynamic and static power dissipation in parallel multiplier partial product reduction tree. Basically, using the information about the input pattern that is going to be applied to the multiplier (such as static probabilities and spatiotemporal correlations), the reduction tree is optimized. The optimization is obtained by selecting the power efficient configurations by searching among the permutations of partial products for each reduction stage. Probabilistic power estimation methods are introduced for leakage and dynamic power estimations. These estimations are used to lead the optimizers to minimum power consumption. Optimization methods, utilizing the arithmetic equivalencies in the partial product reduction trees, are proposed in order to reduce the dynamic power, static power, or total power which is a combination of dynamic and static power. The energy saving is achieved without any noticeable area or speed overhead compared to random reduction trees. The optimization algorithms are extended to include spatiotemporal correlations between primary inputs. As another extension to the optimization algorithms, the cost function is considered as a weighted sum of dynamic power and static power. This can be extended further to contain speed merits and interconnection power. Through a number of experiments the effectiveness of the optimization methods are shown. The average number of transitions obtained from simulation is reduced significantly (up to 35% in some cases) using the proposed optimizations.</p><p>The proposed methods are in general applicable on arbitrary multi-operand adder trees. As an example, the optimization is applied to the summation tree of a class of elementary function generators which is implemented using summation of weighted bit-products. Accurate transistor-level power estimations show up to 25% reduction in dynamic power compared to the original designs.</p><p>Power estimation is an important step of the optimization algorithm. A probabilistic gate-level power estimator is developed which uses a novel set of simple waveforms as its kernel. The transition density of each circuit node is estimated. This power estimator allows to utilize a global glitch filtering technique that can model the removal of glitches in more detail. It produces error free estimates for tree structured circuits. For circuits with reconvergent fanout, experimental results using the ISCAS85 benchmarks show that this method generally provides significantly better estimates of the transition density compared to previous techniques.</p>

Multiplications occur frequently in digital signal processing systems, communication systems, and other application specific integrated circuits. Multipliers, being relatively complex units, are deciding factors to the overall speed, area, and power consumption of digital computers. The diversity of application areas for multipliers and the ubiquity of multiplication in digital systems exhibit a variety of requirements for speed, area, power consumption, and other specifications. Traditionally, speed, area, and hardware resources have been the major design factors and concerns in digital design. However, the design paradigm shift over the past decade has entered dynamic power and static power into play as well. In many situations, the overall performance of a system is decided by the speed of its multiplier. In this thesis, parallel multipliers are addressed because of their speed superiority. Parallel multipliers are combinational circuits and can be subject to any standard combinational logic optimization. However, the complex structure of the multipliers imposes a number of difficulties for the electronic design automation (EDA) tools, as they simply cannot consider the multipliers as a whole; i.e., EDA tools have to limit the optimizations to a small portion of the circuit and perform logic optimizations. On the other hand, multipliers are arithmetic circuits and considering arithmetic relations in the structure of multipliers can be extremely useful and can result in better optimization results. The different structures obtained using the different arithmetically equivalent solutions, have the same functionality but exhibit different temporal and physical behavior. The arithmetic equivalencies are used earlier mainly to optimize for area, speed and hardware resources. In this thesis a design methodology is proposed for reducing dynamic and static power dissipation in parallel multiplier partial product reduction tree. Basically, using the information about the input pattern that is going to be applied to the multiplier (such as static probabilities and spatiotemporal correlations), the reduction tree is optimized. The optimization is obtained by selecting the power efficient configurations by searching among the permutations of partial products for each reduction stage. Probabilistic power estimation methods are introduced for leakage and dynamic power estimations. These estimations are used to lead the optimizers to minimum power consumption. Optimization methods, utilizing the arithmetic equivalencies in the partial product reduction trees, are proposed in order to reduce the dynamic power, static power, or total power which is a combination of dynamic and static power. The energy saving is achieved without any noticeable area or speed overhead compared to random reduction trees. The optimization algorithms are extended to include spatiotemporal correlations between primary inputs. As another extension to the optimization algorithms, the cost function is considered as a weighted sum of dynamic power and static power. This can be extended further to contain speed merits and interconnection power. Through a number of experiments the effectiveness of the optimization methods are shown. The average number of transitions obtained from simulation is reduced significantly (up to 35% in some cases) using the proposed optimizations. The proposed methods are in general applicable on arbitrary multi-operand adder trees. As an example, the optimization is applied to the summation tree of a class of elementary function generators which is implemented using summation of weighted bit-products. Accurate transistor-level power estimations show up to 25% reduction in dynamic power compared to the original designs. Power estimation is an important step of the optimization algorithm. A probabilistic gate-level power estimator is developed which uses a novel set of simple waveforms as its kernel. The transition density of each circuit node is estimated. This power estimator allows to utilize a global glitch filtering technique that can model the removal of glitches in more detail. It produces error free estimates for tree structured circuits. For circuits with reconvergent fanout, experimental results using the ISCAS85 benchmarks show that this method generally provides significantly better estimates of the transition density compared to previous techniques.

Several measurements may be used as error signals to determine how to appropriately control a sound field. These include pressure, particle velocity, energy density and intensity. In this thesis, numerical models are used to show which signals perform best in is free-field active noise control (ANC) using error sensors located in the near field of the sound sources. The second is equalization in a free field and a semi-free field. Minimized energy density total power output (MEDToPO) plots are developed; these indicate the maximum achievable attenuation for a chosen error sensor as a function of location. A global listening area equalization coefficient (GLAEC) is found to evaluate the performance of the equalization methods. It is calculated by finding the average of the spectral standard deviation of several frequency response measurements in a specified listening area. For free-field ANC employing error sensors located in the near field, pressure-based measurements perform the best. For free-field equalization over an extended listening region, total energy density performs best. Equalization of an extended listening region is more successful over a limited low-frequency bandwidth.

Ce manuscrit se focalise sur l’effet de divers matériaux composites sur les différentes problématiques de compatibilité électromagnétique dans un véhicule automobile. Les modèles surfaciques des matériaux diélectriques sont validés en confrontant des résultats de mesures et de simulation de leurs permittivités. Ceux des matériaux conducteurs le sont en confrontant le modèle d’impédance de surface à un modèle filaire et en effectuant des mesures des simulations de paramètres S sur une structure majoritairement constituée par un matériau de ce type. Dans les deux cas, la technique de modélisation donne de bons résultats. L’évaluation de l’effet de ces matériaux sur les problématiques de CEM au niveau d’un véhicule est faite sur un démonstrateur qui intègre les équipements et les faisceaux embarqués dans un véhicule en les représentants par des monopôles et des fils conducteurs. L’évaluation des effets des différents matériaux composites sur les problématiques CEM est faite par mesure et simulation des couplages électromagnétiques à l’intérieur du démonstrateur et entre le démonstrateur et une antenne test. L’analyse des couplages électromagnétiques confirme que le modèle d’impédance de surface reproduit assez bien les comportements des matériaux composites étudiés. Concernant l’effet des matériaux composites sur les problématiques CEM au niveau d’un véhicule, cette étude mène à deux résultats majeurs du point de vue de la compatibilité électromagnétique. Le premier concerne l’usage des matériaux diélectriques qui augmente globalement la plupart des couplages mesurés de 5 dB à 30 dB. Le second porte sur le matériau conducteur étudié qui n’a quasiment aucun effet sur les différents couplages analysés en comparaison de la structure en acier. / The main concern of this thesis is the characterization of the impacts of some composite materials on the main electromagnetic compatibility issues in a vehicle. The surface models of the dielectric materials are validated by confronting their simulated and measured permittivity. The surface model of the studied conductive material is validated by confronting it to a wire model and by measuring and simulating the S parameters on a structure constituted by such a material. It appears in both cases of dielectric and conductive composite materials that the surface impedance modeling technique gives a good description of the materials. The analysis of the effects of these materials on the EMC issues within a vehicle is done by use of a demonstrator representing the car body. The different equipment and harnesses embedded in a vehicle are represented in the demonstrator by some wires and monopoles. The evaluation of the impact of the composite materials on the EMC issues is done by measuring and simulating the different couplings within the demonstrator and between the demonstrator and a test antenna. The analysis of the different couplings confirms that the surface impedance material modeling approach describes well the materials under test. Concerning the impact of the composite materials on the EMC issues at a vehicle level, this analysis fulfills two main results. The first one concerns the dielectric materials. Indeed the use of these materials increases the different coupling by a value varying between at least 5 dB to 30 dB. The second conclusion concerns the use of conductive composite materials. It appears that they have no effect on the different couplings in comparison to the full steel structure.

Η ανίχνευση με τη χρήση μικροκυμάτων παίζει πολύ σημαντικό ρόλο στην τεχνολογική εξέλιξη του κόσμου τα τελευταία 50 χρόνια. Από τα ραντάρ μέχρι τη Μικροκυματική Ραδιομετρία, η ανίχνευση με τη χρήση μικροκυμάτων έχει χρησιμοποιηθεί για έναν αυξανόμενο αριθμό εφαρμογών σε διάφορα επιστημονικά πεδία, μεταξύ των οποίων η χαρτογράφηση του εδάφους, ο καθορισμός της υγρασίας του εδάφους, η θερμογραφία και η ανίχνευση του καρκίνου του μαστού. Έτσι, οι μικροκυματικοί αισθητήρες, διαθέτοντας την ικανότητα να διαπερνούν πολλά είδη μέσων (πχ. σύννεφα, βιολογικοί ιστοί), έχουν μια σημαντική θέση ανάμεσα σε άλλες τεχνικές μέτρησης. Η Μικροκυματική Ραδιομετρία αποτελεί ένα σημαντικό τομέα της επιστημονικής έρευνας και εφαρμογής της ανίχνευσης με τη χρήση μικροκυμάτων, καθώς αποτελεί μια παθητική μέθοδο ανίχνευσης της φυσικά εκπεμπόμενης χαοτικής θερμικής ακτινοβολίας από κάθε σώμα που βρίσκεται σε θερμοκρασία άνω του απόλυτου μηδενός (-273 Κελσίου). Ένα μικροκυματικό ραδιόμετρο είναι η συσκευή που χρησιμοποιείται για τη διεξαγωγή ραδιομετρικών μετρήσεων. Η ραδιομετρία έχει αποτελέσει ένα σημαντικό τομέα έρευνας όχι μόνο για την αξιολόγηση της ατμόσφαιρας και της επιφάνειας της γης, αλλά και για την περαιτέρω διερεύνηση των παθητικών μετρήσεων, με σημαντικές εφαρμογές ειδικά στον τομέα της βιοϊατρικής. Στα πλαίσια της παρούσας Διδακτορικής Διατριβής μελετήθηκε σε θεωρητικό και πειραματικό επίπεδο η βελτιστοποίηση των ιδιοτήτων ανίχνευσης ενός Τρισδιάστατου Συστήματος Παθητικής Μικροκυματικής Ραδιομετρικής Απεικόνισης για διαγνωστικές εφαρμογές εγκεφάλου. Η καινοτομία της προτεινόμενης μεθόδου έγκειται στη χρήση μιας αγώγιμης ελλειψοειδούς κοιλότητας που δρα σαν μορφοποιητής δέσμης, ώστε να επιτευχθεί μέγιστη συγκέντρωση και εστίαση της ακτινοβολίας που εκπέμπει το φυσικό σώμα ενδιαφέροντος, σε συνδυασμό με ευαίσθητους ραδιομετρικούς δέκτες και ομοιοκατευθυντικές κεραίες λήψης στο φάσμα συχνοτήτων 1 – 4 GHz. Η μέτρηση πραγματοποιείται με την τοποθέτηση του ανθρώπινου εγκεφάλου στην περιοχή της πρώτης εστίας και τη λήψη της ακτινοβολίας που συγκλίνει, μέσω ανάκλασης στα τοιχώματα του ελλειψοειδούς, στη δεύτερη εστία. Εκεί είναι τοποθετημένη η κεραία λήψης που συνδέεται στον ευαίσθητο ραδιομετρικό δέκτη. VI Με σκοπό τη βελτίωση των ιδιοτήτων εστίασης του συστήματος, πραγματοποιήθηκε η μοντελοποίησή του και ακολούθησε εκτενής ηλεκτρομαγνητική μελέτη για την ανάλυση της επίδρασης διατάξεων προσαρμογής από κατάλληλα υλικά στο εσωτερικό της ελλειψοειδούς κοιλότητας. Τα αποτελέσματα δείχνουν πως με τη σωστή επιλογή των υλικών και των ιδιοτήτων τους, είναι δυνατό να επιτευχθεί σημαντική βελτίωση του βάθους ανίχνευσης του κατωφλίου ανίχνευσης θερμοκρασίας και της χωρικής διακριτικής ικανότητας του συστήματος. Τα πειράματα με ομοιώματα που πραγματοποιήθηκαν, επαληθεύουν τις βασικές αρχές λειτουργίας του συστήματος καθώς επίσης και την ευεργετική επίδραση των διατάξεων προσαρμογής στις ιδιότητες εστίασής του, που μελετήθηκαν θεωρητικά στο πρώτο στάδιο της έρευνας,. Τέλος, οι πειραματικές διαδικασίες, που σχεδιάστηκαν με βάση πιθανές κλινικές εφαρμογές του συστήματος, δείχνουν ότι έχει βασικά χαρακτηριστικά και ιδιότητες ώστε να αποτελέσει στο μέλλον κλινικό, διαγνωστικό εργαλείο. / Microwave sensing has played an increasingly significant role in the world’s technological advances over the past 50 years. From radar to radiometry, microwave sensing has been used for a large number of applications, including ground mapping, soil moisture determination, thermography, and breast cancer detection. With the ability to safely penetrate many kinds of media (e.g., clouds or biological specimens), microwave sensors find a significant place among other modalities of measurement. Microwave radiometry is an important scientific research and application area of microwave sensing because it provides a passive sensing technique for detecting naturally emitted chaotic thermal radiation by any material object being above the absolute zero temperature (-273 Celsius). A microwave radiometer is the device used to conduct radiometric measurements. While radiometry has been a significant research field for atmospheric and earth surface evaluations, it lends itself to further exploration of passive measurements, with significant applications especially in the biomedical field. In the framework of the present PhD Thesis, a theoretical and experimental optimization study of the sensing capabilities of a Three Dimensional Passive Microwave Radiometry Imaging System for brain diagnostic applications was performed. The novelty of the proposed methodology consists in the use of a conductive ellipsoidal cavity acting as a beamformer to achieve maximum peak of radiation pattern in order to measure the intensity of the microwave energy, radiated by the medium of interest, by using sensitive microwave radiometers and relevant non – contacting antennas within the range of 1 – 4 GHz. The measurement is realized by placing the human brain in the region of the first focus and collecting the radiation converged at the second focus by a receiving antenna connected to the sensitive radiometer. Towards the improvement of the system’s focusing properties, extended electromagnetic analysis was performed in order to validate the impact of matching configurations made from appropriate materials, located inside the ellipsoidal cavity. The results show that with the appropriate choice of materials and careful assessment of their properties, it is possible to significantly improve the system’s detection depth, temperature detection level and spatial sensitivity. VIII The experimental procedures that were performed verify the proof of concept and confirm the beneficial impact of matching configurations on the system’s focusing properties, which was theoretically studied in the first part of the research. Finally, the experimental set used in the study, related to possible clinical applications, produced promising results regarding the potential perspective of the system to serve as a future clinical diagnostic tool.