In dissertation discuss about new created dynamic characteristics establishment of low-frequency (0,7–50 Hz) vibrations isolation system. Presented theoretical and experimental investigations. Main goal of dissertation – is creation of dynamic parameters establishment methods for low-frequency vibration isolation systems and stiff quasi-zero vibrations isolation system, also investigate their dynamical characteristics and usage possibilities. Investigation object – low-frequency vibrations isolation mechanical systems and their dynamic characteristics establishment. Wish to realize investigation goal, were solved those tasks: 1) In scientifically literature investigates types of passive and active vibration isolation systems, constructions, work principals and analyze; 2) Analyzed and theoretically introduced mechanical conceptions of dynamic characteristics establishment methods of the vibration isolation systems; 3) Created stiff quasi-zero vibration isolation method and system based on zeroing of spring stiffness; 4) Done experimental dynamic characteristics evaluations of optics tables with pneumatic isolation and stiff quasi-zero vibration isolation systems; 5) Done vibration measurement uncertainty and given results reliability evaluation. Dissertation contents introduction, three parts, general conclusion of the results, used literature and list of author’s themes published dissertations, three attachments. In introduction part discuss about investigation problems... [to full text] / Disertacijoje nagrinėjamas naujai sukurtų mechaninių pasyviųjų žemojo (0,7–50 Hz) dažnio virpesių izoliavimo sistemų dinaminių charakteristikų nustatymas. Pateikiami teoriniai ir eksperimentiniai tyrimai. Pagrindinis disertacijos tikslas – sukurti mechaninių pasyviųjų žemojo dažnio virpesių izoliavimo sistemų dinaminių parametrų nustatymo metodiką ir kvazinulinio standžio virpesių izoliavimo sistemą, ištirti dinamines jų charakteristikas ir naudojimo galimybes. Tyrimų objektas – žemojo dažnio pasyviosios virpesių izoliavimo mechaninės sistemos ir jų dinaminių charakteristik nustatymas. Siekiant įgyvendinti tyrimų tikslą, išspręsti šie uždaviniai: 1) atlikta mokslinės literatūros apie pasyviųjų ir aktyviųjų virpesių izoliavimo sistemų tipus, konstrukcijas, veikimo principus analizė; 2) išanalizuoti ir pagrįsti mechaninių pasyviųjų virpesių izoliavimo sistemų dinaminių charakteristikų nustatymo metodai; 3) sukurtas kvazinulinio standžio virpesių izoliavimo metodas ir sistema, pagrįsta spyruoklių standžio įnulinimu; 4) atliktas optinių stalų su pneumatiniais izoliatoriais ir kvazinulinio standžio virpesių izoliavimo sistemos eksperimentinis dinaminių charakteristikų įvertinimas; 5) atliktas virpesių matavimo neapibr ėžties ir gautų rezultatų patikimumo įvertinimas. Disertaciją sudaro įvadas, keturi skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai, trys priedai. Įvadiniame skyriuje aptariama tiriamoji problema, darbo... [toliau žr. visą tekstą]

Disertacijoje nagrinėjamas naujai sukurtų mechaninių pasyviųjų žemojo (0,7–50 Hz) dažnio virpesių izoliavimo sistemų dinaminių charakteristikų nustatymas. Pateikiami teoriniai ir eksperimentiniai tyrimai. Pagrindinis disertacijos tikslas – sukurti mechaninių pasyviųjų žemojo dažnio virpesių izoliavimo sistemų dinaminių parametrų nustatymo metodiką ir kvazinulinio standžio virpesių izoliavimo sistemą, ištirti dinamines jų charakteristikas ir naudojimo galimybes. Tyrimų objektas – žemojo dažnio pasyviosios virpesių izoliavimo mechaninės sistemos ir jų dinaminių charakteristik nustatymas. Siekiant įgyvendinti tyrimų tikslą, išspręsti šie uždaviniai: 1) atlikta mokslinės literatūros apie pasyviųjų ir aktyviųjų virpesių izoliavimo sistemų tipus, konstrukcijas, veikimo principus analizė; 2) išanalizuoti ir pagrįsti mechaninių pasyviųjų virpesių izoliavimo sistemų dinaminių charakteristikų nustatymo metodai; 3) sukurtas kvazinulinio standžio virpesių izoliavimo metodas ir sistema, pagrįsta spyruoklių standžio įnulinimu; 4) atliktas optinių stalų su pneumatiniais izoliatoriais ir kvazinulinio standžio virpesių izoliavimo sistemos eksperimentinis dinaminių charakteristikų įvertinimas; 5) atliktas virpesių matavimo neapibr ėžties ir gautų rezultatų patikimumo įvertinimas. Disertaciją sudaro įvadas, keturi skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai, trys priedai. Įvadiniame skyriuje aptariama tiriamoji problema, darbo... [toliau žr. visą tekstą] / In dissertation discuss about new created dynamic characteristics establishment of low-frequency (0,7–50 Hz) vibrations isolation system. Presented theoretical and experimental investigations. Main goal of dissertation – is creation of dynamic parameters establishment methods for low-frequency vibration isolation systems and stiff quasi-zero vibrations isolation system, also investigate their dynamical characteristics and usage possibilities. Investigation object – low-frequency vibrations isolation mechanical systems and their dynamic characteristics establishment. Wish to realize investigation goal, were solved those tasks: 1) In scientifically literature investigates types of passive and active vibration isolation systems, constructions, work principals and analyze; 2) Analyzed and theoretically introduced mechanical conceptions of dynamic characteristics establishment methods of the vibration isolation systems; 3) Created stiff quasi-zero vibration isolation method and system based on zeroing of spring stiffness; 4) Done experimental dynamic characteristics evaluations of optics tables with pneumatic isolation and stiff quasi-zero vibration isolation systems; 5) Done vibration measurement uncertainty and given results reliability evaluation. Dissertation contents introduction, three parts, general conclusion of the results, used literature and list of author’s themes published dissertations, three attachments. In introduction part discuss about investigation problems... [to full text]

This thesis details an in investigation of two problems arising during the testing of a jet engine in a test cell, namely the formation and ingestion of vortices and the generation and propagation of infrasound. Investigation involved the use of computational fluid dynamic as well as analytical tools. The author extended the work of previous researchers by investigating the effect when a suction inlet in surrounded by four walls, (as it is in a test cell). A previously suspected but not documented small region of unsteady vortex was discovered to lie between the steady vortex and no vortex regions. The preferential attachment of the vortex, when formed, to a particular surface was investigated and a low velocity region near that surface has been proven as a possible cause. A cell bypass ratio > 90% was found to be necessary to avoid the formation of vortices in typical situations. Parametric studies (conducted cetaris paribus) on four different geometries and flow parameters were also conducted to determine how they affected the vortex formation threshold. Boundary layer thickness on the vortex attachment surface, upstream vorticity, size of suction inlet was found to have a direct relationship with probability of vortex formation whereas Reynolds number of flow was found to have an inverse relationship. Three hypotheses regarding the generation and propagation of infrasound in test cells were analysed. The first hypothesis states that the fluctuating of flow within the test cell led to a periodic fluctuation of pressure. The second hypothesis predicts a change in flow conditions can leads to a change in the acoustic reflection characteristics of the blast basket perforates. The final hypothesis proposes that changing engine location and size of augmenter, can lead to a reduction in the slip velocity between the engine exhaust jet and the cell bypass flow thus reducing the engine jet noise. The first hypothesis has been disproved using CFD techniques, although the results are as yet inconclusive. The second and third hypotheses have been proven to be potentially feasible techniques to be employed in the future. The changes proposed in the final hypothesis are shown to reduce the engine jet noise by up to 5 dB.

Supporters of a nutritional supplement, β-Hydroxy-β-Methylbutyrate (HMB) supplementation, claim that it will increase the muscular strength gains and lean muscle mass gains seen during a resistance training program. It has been suggested that HMB supplementation does this by preventing muscle damage or by regenerating damaged muscle cell membranes. However, no research has evaluated the effect of HMB supplementation on low frequency fatigue. Therefore, the purpose of this study was to determine if three weeks of HMB supplementation could attenuate the effects of low frequency fatigue caused by eccentric muscle contractions of the tibialis anterior muscle. A total of 33 healthy recreationally active subjects (18 males, 15 females; 23.2 ± 4.3 yr) were recruited for this study. All subjects preformed 4 sets of 25 eccentric contractions of the tibialis anterior muscle through a range of motion of 30 degrees. Recovery measures were taken for 20 minutes after the fatigue protocol and at 48 and 96 hours of recovery. The recovery measures included: Maximum voluntary contraction peak torque, 10 Hz peak torque, 50 Hz peak torque, 10/50 Hz peak torque ratio, and EMG measurements. Each subject served as their own control and limbs were randomly assigned to pre-supplement or post-supplement limbs. Following the pre-supplement fatigue protocol and recovery measures each subject completed three weeks of 3g/day HMB supplementation. After the supplementation period the post-supplement fatigue protocol was completed and recovery measures were taken. The 10 Hz peak torque and the 10/50 Hz torque ratio in the pre-supplement limb was still significantly reduced at the 96-hour recovery measurement time, indicating that it was still showing low frequency muscle fatigue at this time. Furthermore, the post-supplement limb, recovered from the fatigue protocol faster, and did not show any signs of low frequency muscle fatigue at the 48-hour recovery measurement time. In addition the pre-supplement limb had significant maximum voluntary contraction torque deficit at the 48-hour recovery measurement time and the post-supplement limb showed no significant deficits. The main findings of this study were that three weeks of HMB supplementation attenuated low frequency fatigue and maximum voluntary contraction torque reduction after an eccentric fatigue protocol.

Supermassive black holes are leading candidates for the regulation of galaxy growth and evolution over cosmic time, via ‘feedback’ processes, whereby outflows from the Active Galactic Nuclei (AGN) halt star formation within the galaxy. AGN feedback is generally thought to occur in two modes, high-excitation (HERG, or ‘quasar-mode’) and low-excitation (LERG or ’radio-mode’) each having a different effect on the host galaxy. LERGs curtail the growth of the most massive galaxies, whereas HERGs are thought to be activated by mergers/interactions, switching off star formation at high redshift. A critical problem in current extragalactic astrophysics lies in understanding the precise physical mechanisms by which these feedback processes operate, and how they evolve over cosmic time. Radio-loud AGN are an essential tool for studying major feedback mechanisms, as they are found within the largest ellipticals, and hence are beacons for the most massive black holes across the bulk of cosmic time. In this thesis I develop and study existing complete radio samples with extensive new multi-wavelength data in the radio, optical and infrared, aiming to investigate the evolution of AGN feedback modes, and methods to locate and study such systems at the very highest redshifts. This will serve to inform further studies of radio-AGN planned with next generation radio instruments such as the LOw Frequency ARray (LOFAR). Very few radio-loud AGN systems are currently known at high redshifts, and the effectiveness of traditional high redshift selection techniques, such as selection based on steep spectral index, have not been well quantified. A purely evidence-based approach to determining the efficiency of various high redshift selection techniques is presented, using nine highly spectroscopically complete radio samples; although weak correlations are confirmed between spectral index and linear size and redshift, selection first of infrared-faint radio sources remains by far the most efficient method of selecting high-z radio galaxies from complete samples. Radio spectral curvature in four of the complete samples is analysed and the effect of radio spectral shape on the measurement of the radio luminosity function (RLF) of steep-spectrum radio sources is investigated. Below z=1, curvature has negligible effect on the measurement of the RLF, however at higher redshifts, where source numbers are low, the shape of the radio spectrum should be taken into account, as individual source luminosities can change up to 0.1-0.2 dex, and this can in some cases introduce errors in space density measurements of up to a factor of 2-3 where source numbers are low. Building upon these samples, the very first independent determinations of the separate RLFs for high and low excitation radio sources across the bulk of cosmic time are made, out to z=1. Here it is shown that HERGs show very clear signs of strong evolution, in line with theoretical predictions. LERGs also show some very weak evolution with redshift, showing increases in space density of typically around a factor of 2. These measurements are also used to estimate the contribution of LERGs, which typically show weak or no emission lines to the ‘missing redshift’ population, which are sources within the complete samples not identifiable spectroscopically. Complementary to this, a pilot study is presented in selecting ‘missing redshift’ sources which are classed as infra-red faint (IFRS), which show no optical or near-IR identification, and are compact in the radio. Follow up spectroscopy on these candidate high z sources detected no line emission. Finally, work carried out towards the testing and commissioning of the new LOFAR telescope is presented. The findings from this thesis will serve to both streamline and inform high redshift radio-AGN searches and studies planned to be carried out with LOFAR and other multi-wavelength complementary surveys in the near future, and help to open up an as yet unexplored epoch in radio-AGN formation and evolution.

Derivation of an electromagnetic model, regarding the wave propagation in a very long (10 km or more) High Voltage Direct Current (HVDC) power cable, is the central part of this thesis. With an existing “perfect” electromagnetic model there are potentially a wide range of applications.The electromagnetic model is focused on frequencies between 0 and 100 kHz since higher frequencies essentially will be attenuated. An exact dispersion relation is formulated and the propagation constant is computed numerically. The dominating mode is the first Transversal Magnetic (TM) mode of order zero, denoted TM01, which is also referred to as the quasi-TEM mode. A comparison is made with the second propagating TM mode of order zero denoted TM02. The electromagnetic model is verified against real time data from Time Domain Reflection (TDR) measurements on a HVDC power cable. A mismatch calibration procedure is performed due to matching difficulties between the TDR measurement equipment and the power cable regarding the single-mode transmission line model.An example of power cable length measurements is addressed, which reveals that with a “perfect” model the length of an 80 km long power cable could be estimated to an accuracy of a few centimeters. With the present model the accuracy can be estimated to approximately 100 m.In order to understand the low-frequency wave propagation characteristics, an exact asymptotic analysis is performed. It is shown that the behavior of the propagation constant is governed by a square root of the complex frequency in the lowfrequency domain. This thesis also focuses on an analysis regarding the sensitivity of the propagation constant with respect to some of the electric parameters in the model. Variables of interest when performing the parameter sensitivity study are the real relative permittivityand the conductivity.

In this study, impulse response of a multipurpose hall, namely METU Northern Cyprus Campus Auditorium (NCCA) is analyzed and the acoustical quality of the auditorium is evaluated. Suggestions to increase the acoustical satisfaction has been made and to overcome the probability of bass-rise caused by the noise of HVAC systems, a proposal has been made to control low frequency sounds by introducing the volume resonators for the specified frequency. For the study, Odeon, which is used effectively in computer based acoustical simulation studies, is used for the analysis part. In the analysis, a 3D drawing of the hall has been produced by the help of the exact dimensions derived from the original submission of the project by the permission of the authorities.

Les exigences liées aux photodétecteurs modernes font de la maîtrise du niveau de bruit un enjeu majeur pour les technologies de demain. Le Random Telegraph Signal (RTS), à l'origine de « pixels clignotants » en imagerie, gênants pour l'utilisateur comme pour les algorithmes de traitement et d'analyse du signal, fait partie des sources de bruit problématiques. Ce travail en fait l'étude dans les détecteurs infrarouge quantiques refroidis à base de HgCdTe. Le premier chapitre présentera des généralités sur la détection infrarouge, le fonctionnement des photodétecteurs quantiques, le matériau HgCdTe, et le bruit. On exposera ensuite les études réalisées sur le bruit RTS dans les imageurs pour différents domaines de l'infrarouge et trois technologies de fabrication de photodiodes. L'évolution des caractéristiques du bruit (amplitude et fréquence) en fonction de la température du détecteur, du flux de photons reçus, de la polarisation appliquée, ou encore du temps d'intégration seront également analysées. Le troisième chapitre sera consacré à l'origine du bruit RTS. Pour cela, différentes architectures d'étages d'entrée de circuit de lecture et de technologies de fabrication de photodiodes seront passées en revue. Enfin, le dernier chapitre exposera l'étude par Deep Level Transient Spectroscopy des défauts profonds électriquement actifs dans la bande interdite du HgCdTe pour le proche infrarouge (Short Wave InfraRed, à 2,5µm). / Infrared detectors are currently facing two major issues: high operating temperature (HOT) and size, weight, and power (SWaP) requirements. To maintain high performance at higher operating temperatures, pixels exhibiting extra noise such as 1/f noise or Random Telegraph Signal (RTS) noise must be limited. This work study the RTS noise in HgCdTe cooled infrared quantum detectors. The first part concerns generalities about the infrared detection, the physic of quantum photodetectors, the HgCdTe material and the noise. Then we present the studies made on RTS noise for different domains of the infrared spectra and for three technologies of photodiodes (Std, AOP and P/N). The evolution of the main features of RTS noise (frequency and amplitude) as a function of the focal plane array temperature, the flux of photons received, the integration time and the applied polarization will be analyzed. The third part is about the origin of the RTS noise. Two architectures of ReadOut Integrated Circuits (ROIC) and two technologies of photodiodes will be examined. Finally, the last part will present the study of electrically active defects in HgCdTe SWIR (2,5µm) made by Deep Level Transient Spectroscopy.

Dans cette thèse, les propriétés électriques de transistors à nanofils de silicium liées à l'interface oxyde de grille/canal ont été étudiées par le biais de mesures de bruit basse fréquence (bruit 1/f) et de transport dans le canal. Ces transistors nanofils dont les dimensions ont été réduites jusqu'à quelques nanomètres pour la section, représentent une alternative sérieuse pour les futurs nœuds technologiques CMOS. Cependant, la qualité de l'interface oxyde de grille/canal pose question pour transistors dont l'architecture s'étend dans les 3 dimensions, en raison du fort rapport surface/volume inhérent à ces transistors, des différentes orientations cristallographiques de ces interfaces, ou encore des matériaux contraints utilisés pour améliorer les performances électriques. La compréhension des liens entre les propriétés de transport des porteurs dans le canal, qui garantissent en grande partie les performances électriques des transistors, et la qualité de l'interface avec l'oxyde de grille est fond primordiale pour optimiser les transistors nanofils. Les mesures de bruit, associées à l'étude du transport dans le canal, sont un outil puissant et adapté à ces dispositifs tridimensionnels, sans être limité par la taille ultra-réduite des transistors nanofils. Les transistors nanofils étudiés ont été fabriqués à partir de substrats minces SOI, et intègrent un empilement de grille HfSiON/TiN, qui permet de réduire les dimensions tout en conservant les mêmes propriétés électrostatiques. Pour gagner en performances, des contraintes mécaniques ont été introduites dans le canal en silicium : en tension pour les NMOS, par le biais de substrat contraint (sSOI), et en compression pour les PMOS. Un canal en compression uni-axiale peut être obtenu par l'intégration de source/drain en SiGe et/ou par l'utilisation de couches contraintes de type CESL. Des transistors à canal SiGe sur isolant en compression ont également été fabriqués et étudiés. Les caractéristiques électriques des divers transistors nanofils (courbes Id-Vg, compromis Ion-Ioff, mobilité des porteurs) démontrent l'excellent contrôle électrostatique dû à l'architecture 3D, ainsi que l'efficacité de l'ingénierie de contraintes dans les nanofils jusqu'à de faibles longueurs de grilles (~17nm). Des mesures de bruit basse fréquence ont été réalisées sur ces mêmes dispositifs et analysées en fonction des paramètres géométriques de l'architecture nanofils (largeur W, forme de la section, longueur de grille L), et des diverses variantes technologiques. Nous avons démontré que le bruit 1/f dans les transistors nanofils peut être décrit par le modèle de fluctuations du nombre de porteurs (CNF) corrélées aux fluctuations de mobilité (CMF). Le bruit associé aux régions S/D a pu également être intégré dans ce modèle en ajoutant une contribution, en particulier pour les PMOS. Alors que les différentes variantes technologiques ont peu d'effet sur le bruit 1/f, les variations de géométrie en L et W changent la composante de bruit liée aux fluctuations du nombre de porteurs (CNF) de manière inversement proportionnelle à la surface totale (~1/WL). Cette augmentation du bruit est le reflet du transport qui se produit à proximité des interfaces avec l'oxyde. Les différentes orientations des interfaces supérieures et latérales (110) ou (100) présentent la même quantité de pièges d'interface (extrait à partir des mesures de bruit 1/f, en séparant les contributions des différentes faces du nanofil) bien qu'ayant une rugosité différente essentiellement liée au process. En revanche la composante CMF n'est pas altérée par la réduction des dimensions contrairement à la mobilité des porteurs qui décroit fortement avec L. Finalement, les mesures de bruit 1/f ont été comparées aux spécifications ITRS 2013 pour les transistors multi-grilles en vue des futurs nœuds technologiques de la logique CMOS, et démontrent que nos transistors nanofils satisfont les exigences en la matière. / In this thesis, electrical properties of gate oxide/channel interface in ultra-scaled nanowire (NW) MOSFETs were experimentally investigated by carrier transport and low-frequency noise (LFN) characterizations. NW FETs, which have aggressively downscaled cross-section of the body, are strong candidates for near future CMOS node. However, the interface quality could be a critical issue due to the large surface/volume ratio, the multiple surface orientations, and additional strain technology to enhance the performance. Understanding of carrier transport and channel interface quality in NW FETs with advanced high-k/metal gate is thus particularly important. LFN provides deep insights into the interface properties of MOSFET without lower limit of required channel size. LFN measurement thus can be a powerful technique for ultra-scaled NW FETs. Also, fitting mobility (such as low-field mobility) extraction by Y-function method is an efficient method. Omega-gate NW FETs were fabricated from FD-SOI substrates, and with Hf-based high-k/metal gate (HfSiON/TiN), reducing detrimental effects by device downscaling. In addition, strain technologies to the channel were additively processed. Tensile strained-SOI substrate was used for NMOS, whereas compressive stressors were used for PMOS devices. Strained Si channel for PMOS was processed by raised SiGe S/D and CESL formations. Strained SiGe channel (SGOI) was also fabricated for further high-performance PMOS FETs. Firstly, the most common Id-Vg was characterized in single-channel NW FETs as the basic performance. Reference SOI NWs provided the excellent static control down to short channel of 17nm. Stressors dramatically enhanced on-current owing to a modification of channel energy-band structure. Then, extracted low-field mobility in NWs also showed large improvement of the performance by stressors. The mobility extraction effectively evaluated FET performance even for ultra-scaled NWs. Next, LFN investigated for various technological and architectural parameters. Carrier number fluctuations with correlated mobility fluctuations (CNF+CMF) model described 1/f noise in all our FETs down to the shortest NWs. Drain current noise behavior was basically similar in both N- and PMOS FETs regardless of technological splits. Larger 1/f noise stemming from S/D regions in PMOS FETs was perfectly interpreted by the CNF+CMF model completed with Rsd fluctuations. This observation highlighted an advantage of SGOI NW with the lowest level of S/D region noise. Geometrical variations altered the CNF component with simple impact of device scaling (reciprocal to both Wtot and Lg). No large impact of surface orientation difference between the channel (100) top and (110) side-walls in [110]-oriented NWs was observed. Scaling regularity with both Wtot and Lg, without much quantum effect, could be attributed to the use of HfSiON/TiN gate and carrier transport occurring mostly near top and side-wall surfaces even in NW geometry. Meanwhile, the CMF factor was not altered by decreasing dimensions, while the mobility strongly depends on the impact. Extracted oxide trap density was roughly steady with scaling, structure, and technological parameter impacts. Simple separation method of the contributions between channel top surface and side-walls was demonstrated in order to evaluate the difference. It revealed that oxide quality on (100) top and (110) side-walls was roughly comparable in all the [110]-devices. The density values lie in similar order as the recent reports. An excellent quality of the interface with HfSiON/TiN gate was thus sustained for all our technological and geometrical splits. Finally, our NWs fulfilled 1/f LFN requirements stated in the ITRS 2013 for future MG CMOS logic node. Consequently, we concluded that appropriate strain technologies powerfully improve both carrier transport and LFN property for future CMOS circuits consisting of NW FETs, without any large concern about the interface quality.

O ruído de baixa frequência é um limitador de desempenho em circuitos analógicos, digitais e de radiofrequência, introduzindo ruído de fase em osciladores e reduzindo a estabilidade de células SRAM, por exemplo. Transistores de efeito de campo de metalóxido- semicondutor (MOSFETs) são conhecidos pelos elevados níveis de ruído 1= f e telegráfico, cuja potência pode ser ordens de magnitude maior do que a observada para ruído térmico para frequências de até dezenas de kHz. Além disso, com o avanço da tecnologia, a frequência de corner —isto é, a frequência na qual as contribuições dos ruídos térmico e shot superam a contribuição do ruído 1= f — aumenta, tornando os ruídos 1= f e telegráfico os mecanismos dominantes de ruído na tecnologia CMOS para frequências de até centenas de MHz. Mais ainda, o ruído de baixa frequência em transistores nanométricos pode variar significativamente de dispositivo para dispositivo, o que torna a variabilidade de ruído um aspecto importante para tecnologias MOS modernas. Para assegurar o projeto adequado de circuitos do ponto de vista de ruído, é necessário, portanto, identificar os mecanismos fundamentais responsáveis pelo ruído de baixa frequência em MOSFETs e desenvolver modelos capazes de considerar as dependências do ruído com geometria, polarização e temperatura. Neste trabalho é proposta uma técnica para análise de ruído de baixa frequência baseada na autocorrelação dos espectros de ruído em função de parâmetros como frequência, polarização e temperatura. A metodologia apresentada revela informações importantes sobre os mecanismos responsáveis pelo ruído 1= f que são difíceis de obter de outras formas. As análises de correlação realizadas em três tecnologias CMOS comerciais (140 nm, 65 nm e 45 nm) fornecem evidências contundentes de que o ruído de baixa frequência em transistores MOS tipo-n e tipo-p é composto por um somatório de sinais telegráficos termicamente ativados. / Low-frequency noise (LFN) is a performance limiter for analog, digital and RF circuits, introducing phase noise in oscillators and reducing the stability of SRAM cells, for example. Metal-oxide-semiconductor field-effect-transistors (MOSFETs) are known for their particularly high 1= f and random telegraph noise levels, whose power may be orders of magnitude larger than thermal noise for frequencies up to dozens of kHz. With the technology scaling, the corner frequency — i.e. the frequency at which the contributions of thermal and shot noises to noise power overshadow that of the 1= f noise — is increased, making 1= f and random telegraph signal (RTS) the dominant noise mechanism in CMOS technologies for frequencies up to several MHz. Additionally, the LFN levels from device-to-device can vary several orders of magnitude in deeply-scaled devices, making LFN variability a major concern in advanced MOS technologies. Therefore, to assure proper circuit design in this scenario, it is necessary to identify the fundamental mechanisms responsible for MOSFET LFN, in order to provide accurate LFN models that account not only for the average noise power, but also for its variability and dependences on geometry, bias and temperature. In this work, a new variability-based LFN analysis technique is introduced, employing the autocorrelation of multiple LFN spectra in terms of parameters such as frequency, bias and temperature. This technique reveals information about the mechanisms responsible for the 1= f noise that is difficult to obtain otherwise. The correlation analyses performed on three different commercial mixed-signal CMOS technologies (140-nm, 65-nm and 40-nm) provide strong evidence that the LFN of both n- and p-type MOS transistors is primarily composed of the superposition of thermally activated random telegraph signals (RTS).