Abstract This thesis describes the development of low-voltage, low-power circuit blocks and structures for portable, battery-operated applications such as heart rate detectors, pacemakers and hearing-aid devices. In this work, the definition for low supply voltage operation is a voltage equal to or less than the minimum supply voltage needed to operate an analogue switch, i.e. VDD(min) ≤ 2VT + Vov, which enables the use of a single cell battery whose polar voltage is 1 – 1.5 V. The targeted power consumption is in a range of microwatts. The design restrictions for analogue circuit design caused by the low supply voltage requirement of the latest and future CMOS process technologies were considered and a few circuit blocks, namely two operational amplifiers, a Gm–C filter and a bandgap voltage reference circuit, were first designed to investigate their feasibility for the above-mentioned low-voltage and low-power environment. Two operational amplifiers with the same target specifications were designed with two different types of input stages, i.e. a floating-gate and a bulk-driven input stage, in order to compare their properties. Based on the experiences collected from the designed circuit blocks, an analogue CMOS preprocessing stage for a heart rate detector and a self-calibrating RC oscillator for clock and resistive/capacitive sensor applications were designed, manufactured and tested. The analogue preprocessing stage for a heart rate detector includes a continuous-time offset-compensated preamplifier with a gain of 40 dB, an 8th-order switched-opamp switched-capacitor bandpass filter, a 32-kHz crystal oscillator and a bias circuit, and it achieves the required performance with a supply voltage range of 1.0 – 1.8 V and a current consumption of 3 μA. The self-calibrating RC oscillator operates with supply voltages of 1.2 – 3.0 V and achieves a tunable frequency range of 0.2 – 150 MHz with a total accuracy of ±1% within a supply voltage range of 1.2 – 1.5 V, a temperature range from -20 to 60 °C and a current consumption of less than 70 μA @ 5 MHz with external high precision resistor and capacitor. The measurement results prove that the developed low-voltage low-power analogue circuit structures can achieve the required performance and therefore be successfully implemented with modern CMOS process technologies with limited supply voltages. / Tiivistelmä Tämä väitöskirja käsittelee matalan käyttöjännitteen pienitehoisten piirirakenteiden kehittämistä kannettaviin, paristokäyttöisiin sovelluksiin kuten esimerkiksi sykemittareihin, sydämen tahdistimiin ja kuulolaitteisiin. Matalalla käyttöjännitteellä tarkoitetaan jännitettä, joka on pienempi tai yhtäsuuri kuin analogisen kytkimen tarvitsema pienin mahdollinen käyttöjännite, VDD(min) ≤ 2VT + Vov, joka mahdollistaa piirin toiminnan yhdellä paristolla, jonka napajännite on 1 – 1,5 V. Tavoiteltu tehonkulutus on mikrowattiluokkaa. Piirirakenteiden suunnittelussa otettiin huomioon viimeisimpien ja lähitulevaisuuden CMOS-valmistusteknologioiden aiheuttamat matalan käyttöjännitteen erityisvaatimukset ja niiden pohjalta kehitettiin aluksi kaksi erilaista operaatiovahvistinta, GmC-suodatin, ja bandgap-jännitereferenssi. Operaatiovahvistimet toteutettiin samoin tavoitevaatimuksin kahdella eri tekniikalla käyttäen toisen vahvistimen tuloasteessa ns. kelluvahilaisia tulotransistoreita ja toisen tuloasteessa ns. allasohjattuja tulotransistoreita. Kehitetyistä rakenteista saatujen kokemusten pohjalta suunniteltiin, valmistettiin ja testattiin kaksi erilaista CMOS-teknologialla toteutettua mikropiiriä, jotka olivat analoginen esikäsittelypiiri sydämen sykkeen mittaukseen ja itsekalibroiva RC-oskillaattori resistiivisiin/kapasitiivisiin sensorisovelluksiin. Sydämen sykkeen esikäsittelypiiri sisältää jatkuva-aikaisen, offset-kompensoidun esivahvistimen, jonka vahvistus on 40 dB, kytketyistä kapasitansseista ja kytketyistä operaatiovahvistimista koostuvan kahdeksannen asteen kaistanpäästösuodattimen, 32 kHz kideoskillaattorin ja bias-piirin. Esikäsittelypiiri saavuttaa vaadittavan suorituskyvyn 1,0 – 1,8 V käyttöjännitteellä ja 3 μA virrankulutuksella. Itsekalibroivan RC-oskillaattorin käyttöjännitealue puolestaan on 1,2 – 3,0 V ja käyttökelpoinen taajuusalue 0,2 – 150 MHz. Ulkoista tarkkuusvastusta ja kondensaattoria käytettäessä oskillaattori saavuttaa ±1 % tarkkuuden 1,2 – 1,5 V käyttöjännitteillä ja -20 – 60 °C lämpötila-alueella virrankulutuksen jäädessä alle 70 μA @ 5 MHz. Mittaustulokset osoittavat, että kehitetyt matalan käyttöjännitteen pienitehoiset analogiset rakenteet saavuttavat vaadittavan suorituskyvyn ja voidaan näin ollen menestyksekkäästi valmistaa moderneilla matalan käyttöjännitteen CMOS-teknologioilla.

The purpose of this bachelor thesis is to assess whether it is possible to create a simplified model that estimates the hosting capacity of a low-voltage grid. The Simplified model is compared with a more elaborate model created by the Built Environment Energy Systems Group (BEESG) at Uppsala University. The Simplified model takes three easily obtainable variables into account. The model created by BEESG allows us to observe both the amount of photovoltaic (PV) power that is installed as well as the voltages in each bus in a grid. The hosting capacity is found by gradually increasing the amount of PV power installed in a low-voltage grid until overvoltage is reached. Simulations with BEESG’s model are done for a week in July when the PV generation has its peak and the load is generally low. The Simplified model is created using linear regression with the calculated values from the BEESG’s model as a reference. The report shows that the Simplified model will give an estimation of the low-voltage grid’s hosting capacity that is comparable to the value calculated with BEESG’s model. The results show that it is rarely the low-voltage grid that restricts the installation of PV facilities and that a high self-consumption is advantageous regarding to the grids hosting capacity.

The main outcome of this research is the development of a Probabilistic Impact Assessment methodology to comprehensively understand the effects of low carbon technologies (LCTs) in low voltage (LV) distribution networks and the potential solutions available to increase their adoption. The adoption of LCTs by domestic customers is an alternative to decreasing carbon emissions. Given that these customers are connected to LV distribution networks, these assets are likely to face the first impacts of LCTs. Thus, to quantify these problems a Monte Carlo-based Probabilistic Impact Assessment methodology is proposed in this Thesis. This methodology embeds the uncertainties related to four LCTs (PV, EHPs, µCHP and EVs). Penetration levels as a percentage of houses with a particular LCT, ranging from 0 to 100% in steps of 10%, are investigated. Five minute time-series profiles and three-phase four-wire LV networks are adopted. Performance metrics related to voltage and congestion are computed for each of the 100 simulations per penetration level. Given the probabilistic nature of the approach, results can be used by decision makers to determine the occurrence of problems according to an acceptable probability of technical issues. To implement the proposed methodology, electrical models of real LV networks and high resolution profiles for loads and LCTs are also developed. Due to the historic passive nature of LV circuits, many Distribution Network Operators (DNOs) have no model for them. In most cases, the information is limited to Geographic Information Systems (GIS) typically produced for asset management purposes and sometimes with connectivity issues. Hence, this Thesis develops a methodology to transform GIS data into suitable computer-based models. In addition, thousands of residential load, PV, µCHP, EHP and EV profiles are created. These daily profiles have a resolution of five minutes. To understand the average behaviour of LCTs and their relationship with load profiles, the average peak demand is calculated for different numbers of loads with and without each LCT.The Probabilistic Impact Assessment methodology is applied over 25 UK LV networks (i.e., 128 feeders) for the four LCTs under analysis. Findings show that about half of the studied feeders are capable of having 100% of the houses with a given LCT. A regression analysis is carried out per LCT, to identify the relationships between the first occurrence of problems and key feeder parameters (length, number of customers, etc.). These results can be translated into lookup tables that can help DNOs produce preliminary and quick estimates of the LCT impacts on a particular feeder without performing detailed studies. To increase the adoption of LCTs in the feeders with problems, four solutions are investigated: feeder reinforcement, three-phase connection of LCTs, loop connection of LV feeders and implementation of OLTCs (on-load tap changers) in LV networks. All these solutions are embedded in the Probabilistic Impact Assessment. The technical and economic benefits of each of the solutions are quantified for the 25 networks implemented.

Neste trabalho, apresenta-se um método para o Planejamento de Redes de Distribuição Secundária. O modelo básico desenvolvido baseia-se em técnica de programação dinâmica a fim de selecionar a política de evolução de trocas de transformadores de distribuição e rede secundária, com mínimo custo operacional dentro de limites de qualidade de serviço, para o atendimento de carga crescente no tempo em uma área de estudo restrita. Inicialmente, apresenta-se a filosofia básica do método, incluindo-se os dados necessários, critérios de planejamento e metodologia para o cálculo elétrico de redes secundárias. Em sequência, são apresentados três modelos para a solução do problema; tais modelos são diferenciados pela eliminação progressiva de hipóteses simplificativas. Nos dois primeiros modelos, a carga e seu crescimento são supostos uniformemente distribuídos ao longo dos trechos da rede secundária. No terceiro modelo, a distribuição da carga dos pontos presentes na rede secundária, durante o período de estudo, é estabelecida por procedimento randômico, com o único vínculo de serem mantidos os mercados globais de demanda e número de consumidores na área em estudo. Posteriormente, estabelece-se um exemplo de aplicação que permite proceder à comparação entre os três modelos desenvolvidos. Finalizando o trabalho, são estabelecidas as conclusões, possibilidades de aplicação do método em diversos estudos do sistema de Distribuição Secundária e são tecidos comentários sobre tópicos para ulterior desenvolvimento. / This work focuses on a method for the Planning of Secondary Distribution Systems. The basic model deals with dynamic programming in order to get an optimized design - Distribution Transformer and Secondaries - which presents the lowest operation cost within service quality limits in order to supply growing load on a restricted area. Initially the basic concepts of the method are presented, including the establishment of the data base, planning criteria and methodology in order to get operating conditions at secondary networks. Concerning this method, three computational models were established. These models differ form each other as far as some of the simplified hypothesis are eliminated. The first two models consider a uniform distribution of loads along the secondary system. The third model establishes a randomic distribution of loads on the restricted studying area. Following an application example, comparison is proceeded among the developed models. Eventually the conclusions, some possible applications of the method on Distribution system studies and research topics for further developments are settled.

This work deals with issues of design and optimize of an operational amplifiers using CMOS transistor models. The main focus of work is to propose a circuit suitable for low voltage applications with low power. The proposed circuit consists of sub-circuits, each of which must operate in the desired voltage range. Detailed design of input and output stages will reach range of rail-to-rail type with a minimum quiescent current.

This diploma thesis aims to briefly interpret problems relating to continuity of distribution of electrical energy in a distribution network of low voltage. It also mentions methods of calculation of a distribution system´s reliability which are the most used in practice. Next, there is a chapter dedicated to how distribution networks are projected and operated in the Czech Republic and in the United Kingdom. Based on experiences with meshed networks operation this thesis designs protection of meshed distribution network of low voltage. In the end, a non-sequential method of Monte Carlo is used to calculate System Average Interruption Index (SAIDI) and System Average Interruption Frequency index (SAIFI).

This thesis concentrates on the methodology of semiconductor samples preparation for low voltage scanning electron microscopy. In the first part a detailed theory of sample imaging using electron beam and difference between classical scanning electron microscopy (SEM) and low voltage scanning electron microscopy (LVSEM) is described. It is given a description of a contrast formation in SEM and LVSEM and theories describing a contrast formation of differently doped semiconductors. The second part contains experimental data. The advantages and disadvantages of cleavage and focused ion beam (FIB) milling as sample preparation techniques are discussed. FIB was found as the best method for sample preparation for the analysis of precisely defined location on the sample. It is necessary to use the lowest possible FIB accelerating voltage for final polishing, ideally 1 kV.

Die Berechnung der Netzverluste in Niederspannungsnetzen kann nur über Umwege erfolgen, da viele Netzbetreiber keine digitalisierten Daten ihrer Netze besitzen. Hier wird ein Ansatz zur Ermittlung der technischen Verluste anhand vorhandener Netzdaten beschrieben. / The major part of network operator of low voltage nets do not have digitised data of their nets. That’s why net losses must be calculated indirectly. This article describes an approach for getting results in a direct way.

In the present study, we sought to investigate the agreement between late gadolinium enhancement (LGE) in cardiovascular magnetic resonance (CMR) and electro-anatomical maps (EAM) of patients with non-ischemic dilated cardiomyopathy (NIDCM) and how it relates with the procedural outcome after catheter ablation of ventricular arrhythmias (VA). We identified 50 patients with NIDCM who underwent CMR and ablation for VA. LGE was detected in 16 patients (32%), mostly in those presenting with sustained VT (15 patients). Low-voltage areas (<1.5 mV) were observed in 23 patients (46%), in 7 patients (14%) without evidence of LGE. Using a threshold of 1.5 mV, a good and partially good agreement between the bipolar EAM and LGE-CMR was observed in only 4 (8%) and 9 (18%) patients, respectively. With further adjustments of EAM to match the LGE, we defined new cut-off limits of median 1.5 mV and 5 mV for bipolar and unipolar maps, respectively. Most VT exits were found in areas with LGE (12 out of 16 patients). VT exits were found in segments without LGE in 2 patients with unsuccessful ablation as well as in 2 patients with successful ablation, P=0.77. In patients with VT recurrence, the LGE volume was significantly larger than in those without recurrence: 12.2 ± 5.8% vs. 6.9 ± 3.4%; P=0.049. Myocardial heterogeneity provides the electrophysiological substrate of ventricular arrhythmias in patients with myocardial infarction. Fibrosis and reduction in the number of gap junctions of surviving myocytes allow the occurrence of re-entry (23). However, the relationship between fibrosis and VA is complex and involves not only fixed anatomical barriers but also functional blocks caused by differences in the fiber orientation, myocardial thickness mismatch or connexin downregulation (24-26). Studies involving EAM in patients with scar-related VT demonstrated that homogenization of the low-voltage areas with elimination of the signals showing abnormal amplitude and fractionation was associated with improved acute and long-term success rates (27). On the other hand, animal studies showed that CMR can be useful to characterize LV fibrosis. Moreover, the amount of LGE has been associated with inducibility of VT and is considered a powerful and independent predictor of adverse prognosis, especially in myocardial infarction patients (28-29). In contrast to ischemic cardiomyopathy, LGE is infrequently found in patients with NIDCM. A previous study of 399 patients with NIDCM demonstrated that LGE was detected in approximately one-fourth of the patients and was associated with a 9-fold increase of risk for SCD (30). In accordance with these data, we observed LGE in approximately one third of the patients, and most of them had a history of spontaneous sustained VT. In contrast to the VT patients who have frequently LGE, all patients with ventricular premature beats but without any sustained VT did not show any evidence of LGE in CMR. These observations support the general understanding that the presence of LGE identifies more advanced cardiomyopathy as well as a higher risk for more malignant ventricular arrhythmias. Although myocardial fibrosis is associated with a higher likelihood for VT occurrence, the absence of LGE in CMR does not completely eliminate the risk for VT. Some patients had sustained ventricular arrhythmias even without detectable scar in CMR, which suggests a poorer negative predictive value for the LGE. Although CMR imaging is currently considered the reference standard for the detection of LV scar, it has a limited spatial resolution in vivo. Therefore, minute scars as well as diffuse fibrosis that can still trigger VA may remain undetected. The alternative approach to detect myocardial scar is to characterize the electrical properties of the myocardium by using bipolar EAM in order to find low-voltage areas and late potentials that are markers of abnormal tissue. However, abnormal fragmentation and amplitudes below 1,5 mV are less frequently found in NIDCM in comparison to post-myocardial infarction patients. These findings illustrate the downsides of the EAM in NIDCM. Moreover, numerous animal and clinical studies underlined other technical drawbacks of the EAM that can influence the size and the characteristics of the low-voltage areas such as mapping electrode size and spacing, the angle of contact with the underlying tissue, wave-front direction (31-33). Recently, Betensky and al. analyzed the agreement between CMR and EAM in patients with NIDCM and found a significant discordance between both approaches in 36% of the patients. Using lower signal intensity threshold of 2 standard deviations they increased the CMR-EAM agreement up to almost 90% (34). In contrast to Betensky, who used a simplified approach analyzing only the septal to lateral disagreement, we choose to perform more precise analysis using the 17 segments AHA model of the LV. We found 23 out of 50 patients with low-voltage areas and 15 (71.4%) of them had sustained VT. Moreover only 16 (32%) patients with low-voltage had also LGE in the CMR. In our study the basal inferolateral, inferior and infero-septal segments were most frequently affected by LGE in contrast to the basal anterior and anteroseptal segments affected in the EAM. However, in the LGE positive patients, the best pace-mapping sites of the clinical VT coincided with areas of LGE. One possible explanation for the low correlation between EAM and LGE-CMR is the non-transmurality of the fibrosis in patients with NIDCM. A previous study in post-infarct patients demonstrated that median bipolar voltage <1.5 mV was only found in segments demonstrating ≥75% infarct transmurality (35). In a recently published article, Zeppenfeld et al. found that EAM voltages showed a linear relationship with the LV wall thickness and the amount of fibrosis in patients with non-ischemic DCM. However, no cutoff value for the voltage could be found to reliably delineate fibrotic areas in NIDCM (36). Regarding the quantification of the arrhythmogenic substrate, we could not find any correlation between the amount of LGE and the size of the low-voltage areas (endo- or epicardial), which can be explained by the impact of LGE transmurality as well as the sparse distribution of the LV fibrosis. In this regard, an advantage of the LGE-CMR is that it can visualize the presence of intramyocardial and epicardial scar which are not visible by endocardial EAM. The reason is that the bipolar EAM has narrower field of view and proved insensitive to delineate scar that lies deeper within the myocardium (37). Previously, Hutchinson et al. reported that by using a unipolar 8.27 mV threshold endocardial it was possible to identify epicardial bipolar low-voltage areas consistent with macroscopic scarring in patients with NIDCM and normal endocardial bipolar voltage (38). However, we found that the agreement between LGE and unipolar maps using this cutoff of 8.27 mV was poor. After adjusting the unipolar and bipolar threshold on the basis of CMR, the resulting median thresholds for the bipolar and unipolar low-voltage maps were 1.5 mV and 5 mV respectively, which are close to those observed in a previous study (37). 4.1 Conclusions LGE was observed in approximately one-third of the patients with dilated cardiomyopathy of non-ischemic origin and ventricular arrhythmias. LGE was seen mainly in patients with sustained VT. The agreement between the distribution or the extent of LGE and bipolar low-voltage areas was fairly poor. No particular cutoff values for bipolar and unipolar electro-anatomical maps could be found. On the other hand, most VT exits in patient with sustained VT were found in areas of LGE. The procedural success after VA ablation were related to LGE volume only.

Power line communication has been around in past decades and gained renewed attention thanks to the demand of high-speed Internet access. With the significant advantages of existing infrastructure and accessibility to even remote areas, power grid has become one of the promising competitors for multi-media transmission in household. However, the power line was not oriented for data transmission providing a rather hash environment. To overcome the difficulties, advanced modulation and channel coding schemes should be employed. In the thesis low density parity check code (LDPC) is employed to reduce the loss caused by various kinds of effects in the channel especially the noise since its performance approaches to Shannon capacity limit. Moreover, OFDM multi-carrier transmission technique is involved which could decrease the inter-symbol interference and frequency selective fading. Nevertheless, LDPC decoding process was designed specifically for the common Gaussian white noise condition, combined with OFDM modulation the system still could not provide satisfying and practicable performance so improvements are needed for the system. The main works of the thesis are as follows. Set up an environment of power line transmission investigating and simulating the channel characteristics; employ multi-path channel model and Class‐A noise model for further developing the improvement algorithms to deal with the selective fading and impulse noise. Two algorithms proposed here are from different perspectives: the first one is modifying initial posterior information for LDPC decoding and the second one aims at suppressing the impulse noise after demodulation. Finally, a few simulations are performed to reveal the effectiveness of proposed methods. As a result, the improved scheme shows a great superiority improving the performance by no less than 5dB compared to traditional system.