A 10 GHz oversampling delta modulating analogue-to-digital converter implemented with hybrid superconducting digital logic

Thesis (MScEng)--University of Stellenbosch, 2001.ENGLISH ABSTRACT: Rapid Single Flux Quantum (RSFQ) logic cells are discussed, and new cells developed. The expected yield of every cell is computed through a Monte Carlo analysis, and where necessary these cells are optimized for use in a complex system. A mathematical study of the Josephson junction and SQUIDs (Superconducting Quantum Interference devices) as switching elements precede a discussion on the operation of RSFQ and COSL (Complementary Output Switching Logic.) These logic families are implemented in low temperature niobium technology, and require liquid helium cooling. A 10 GHz oversampling delta modulating analogue-to-digital converter is then designed and constructed using RSFQ and COSL building blocks in a hybrid configuration. The design emphasis is on devising ways to test the operation of RSFQ with limited equipment. Yield analysis procedures on the complex system are discussed, followed by a detailed discussion on the circuit layout and layout problems. Software routines are developed to calculate the required dimensions of layout structures.AFRIKAANSE OPSOMMING: Rapid Single Flux Quantum (RSFQ) logiese selle word bespreek, en enkele nuwe selle word ontwikkel. Die verwagte opbrengs, of kans dat 'n sel sal werk, word bereken deur 'n Monte Carlo analise. Waar nodig word selle met behulp van die analise verbeter vir gebruik in 'n komplekse stelsel. 'n Wiskundige studie van die Josephson-vlak en SQUIDs (Superconducting Quantum Interference devices) word gevolg deur 'n bespreking oor die werking van RSFQ en COSL (Complementary Output Switching Logic.) Hierdie logiese families word geïmplementeer in laetemperatuur niobiumtegnologie, en vereis vloeibare helium-verkoeling. 'n Deltamodulerende analoog-na-digitale omsetter met 'n intree-monstertempo van 10 GHz word ontwerp en vervaardig met 'n hibriede samestelling van RSFQ en COSL boublokke. Die ontwerp fokus op maniere om die werking van RSFQ teen 10 GHz te kan toets met die beperkte toerusting wat beskikbaar is. Opbrengsanalise op die komplekse stelsel word bespreek, gevolg deur 'n volledige bespreking van die stroombaanuitlegprosedure en uitlegprobleme. Roetines word in sagteware ontwikkel om die nodige dimensies van uitlegstrukture te bereken

A tool kit for the design of superconducting programmable gate arrays

Thesis (PhD)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: The development of a tool kit for the design of superconducting programmable gate arrays (SPGAs) is discussed. A circuit optimizer using genetic algorithms is developed and evaluated. Techniques and a program are also developed for the generation of segmentized 3D models with which to calculate inductance in circuit structures through FastHenry. The ability to add random variations to the dimensions of the models is included. These tools are then used to design novel latching elements that allow the construction of reprogrammable Rapid Single Flux Quantum (RSFQ) circuits. A circular process is used, whereby layouts are converted back to circuit diagrams through element extraction, and reoptimized if necessary. Two programmable frequency dividers are then designed; one for testing the routing and switch structures and programming architecture of an SPGA, and another compact one for testing the latching elements and off-chip interface. The dissertation concludes with an overview of the circuits necessary for the implementation of a fully functional SPGA.AFRIKAANSE OPSOMMING: Die ontwikkeling van ’n gereedskapstel vir die ontwerp van supergeleier FPGA’s (SPGA’s) word bespreek. Eerstens word ’n stroombaanoptimeerder, wat met genetiese algoritmes funksioneer, ontwikkel en geëvalueer. Daarna word tegnieke en ’n program ontwikkel om driedimensionele segmentmodelle te genereer waaruit FastHenry die induktansie van stroombaanstrukture kan bepaal. Die vermoë om toevalsveranderinge by die dimensies van die modelle te voeg, is ook ingesluit. Hierdie gereedskap word dan gebruik om nuwe grendelelemente te ontwerp waarmee herprogrammeerbare Rapid Single Flux Quantum (RSFQ) stroombane gebou kan word. ’n Sirkulêre proses word gevolg, waarvolgens uitlegte na stroombaandiagramme teruggeskakel kan word (deur elementonttrekkings) en, indien nodig, heroptimeer kan word. Twee programmeerbare frekwensiedelers word daarna ontwerp; een om die pulsvervoer- en skakelstrukture, asook programmeringsargitektuur van ’n SPGA te toets, en ’n ander, kompakter een om die grendelelemente en warmlogika koppelvlakke mee te toets. Die proefskrif sluit af met ’n oorsig oor die stroombane benodig vir die implementering van ’n volledig funksionele SPGA

Numerical approach for inductance determination of SQUID washers

1EOrA-08International audienc

Analysis of a Shielding Approach for Magnetic Field Tolerant SFQ Circuits

International audienceThe operating margins of unshielded SFQ circuits are influenced by external magnetic fields, and earlier research showed experimental results of operating region versus bias current for circuits with in-plane and perpendicularly applied magnetic fields. Here, we report a method that can be used to analyze shields to protect SFQ circuits from external magnetic fields. To validate the approach, we investigated a grid-patterned shield of varying spacing. The analysis was done with cell layouts made according to the Hypres' 4.5 kA/cm 2 process, in which the top-most layer, M3, was used to implement the shields. It was calculated that a grid shield of 2.5 μm grid bar width and spacing of 5 μm offered a good compromise at both providing shielding and causing a relatively small drift in circuit inductance. In order to make SFQ circuits more tolerant to magnetic fields, we have simulated with circuit parameter alterations to realize the best bias and higher operating held margins, due to external magnetic fields. The external magnetic fields are modeled through three orthogonal coils that generate roughly a uniform magnetic held density throughout the cell under test

Leveraging digitilisation and machine learning for improved railway operations and maintenance

The efficient and safe movement of goods and people require reliable railway systems. Quality assurance of manufactured and assembled systems and correct maintenance of such systems are required to keep rolling stock in good operational condition. Quality assurance and maintenance in the railway industry can be costly and time-consuming, but the expansive growth of data due to smart sensors and monitoring technologies makes it possible to leverage the potential of machine learning to reduce cost and labour. Improved reliability and safety, and reduced costs are benefits that the use of “Big Data” and machine learning techniques can realise. However, despite these potential benefits for manufacturers, rail operators, and passengers, the rail industry is still labelled for its lack of innovation, while in most other industries, data is regarded as a strategic asset for competitive advantage. This paper demonstrates how machine learning and data analysis can be used to benefit railway industry manufacturers and operators when applied to rolling stock data. It also illustrates the lost opportunity in the rail industry for not applying data-driven solutions to their full potential. The paper also discusses the current applications of machine learning in the railway industry and provides the requirements for the implementation of machine learning techniques. Machine learning is applied to pantograph data of a South African railway operator's rolling stock. Classification – a machine learning technique – is used to identify and categorise events within the dataset to discover whether pantograph bounce occurs due to faulty sensors, faulty pantographs, or defective infrastructure. In this paper it is demonstrated how machine learning can benefit rail manufacturers and operators to improve manufacturing and assembly processes, as well as maintenance practices. It is concluded that railways should treat data similarly to other railway assets, with suitable management and governance practices