Realization of Integrable Low- Voltage Companding Filters for Portable System Applications

Undoubtedly, today’s integrated electronic systems owe their remarkable performance primarily to the rapid advancements of digital technology since 1970s. The various important advantages of digital circuits are: its abstraction from the physical details of the actual circuit implementation, its comparative insensitiveness to variations in the manufacturing process, and the operating conditions besides allowing functional complexity that would not be possible using analog technology. As a result, digital circuits usually offer a more robust behaviour than their analog counterparts, though often with area, power and speed drawbacks. Due to these and other benefits, analog functionality has increasingly been replaced by digital implementations. In spite of the advantages discussed above, analog components are far from obsolete and continue to be key components of modern electronic systems. There is a definite trend toward persistent and ubiquitous use of analog electronic circuits in day-to-day life. Portable electronic gadgets, wireless communications and the widespread application of RF tags are just a few examples of contemporary developments. While all of these electronic systems are based on digital circuitry, they heavily rely on analog components as interfaces to the real world. In fact, many modern designs combine powerful digital systems and complementary analog components on a single chip for cost and reliability reasons. Unfortunately, the design of such systems-on-chip (SOC) suffers from the vastly different design styles of analog and digital components. While mature synthesis tools are readily available for digital designs, there is hardly any such support for analog designers apart from wellestablished PSPICE-like circuit simulators. Consequently, though the analog part usually occupies only a small fraction of the entire die area of an SOC, but its design often constitutes a major bottleneck within the entire development process. Integrated continuous-time active filters are the class of continuous-time or analog circuits which are used in various applications like channel selection in radios, anti-aliasing before sampling, and hearing aids etc. One of the figures of merit of a filter is the dynamic range; this is the ratio of the largest to the smallest signal that can be applied at the input of the filter while maintaining certain specified performance. The dynamic range required in the filter varies with the application and is decided by the variation in strength of the desired signal as well as that of unwanted signals that are to be rejected by the filter. It is well known that the power dissipation and the capacitor area of an integrated active filter increases in proportion to its dynamic range. This situation is incompatible with the needs of integrated systems, especially battery operated ones. In addition to this fundamental dependence of power dissipation on dynamic range, the design of integrated active filters is further complicated by the reduction of supply voltage of integrated circuits imposed by the scaling down of technologies to attain twin objective of higher speed and lower power consumption in digital circuits. The reduction in power consumption with decreasing supply voltage does not apply to analog circuits. In fact, considerable innovation is required with a reduced supply voltage even to avoid increasing power consumption for a given signal to noise ratio (S/N). These aspects pose a great hurdle to the active filter designer. A technique which has attracted the attention of circuit designers as a possible route to filters with higher dynamic range per unit power consumption is “companding”. Companding (compression-expansion) filters are a very promising subclass of continuous-time analog filters, where the input (linear) signal is initially compressed before it will be handled by the core (non-linear) system. In order to preserve the linear operation of the whole system, the non-linear signal produced by the core system is converted back to a linear output signal by employing an appropriate output stage. The required compression and expansion operations are performed by employing bipolar transistors in active region or MOS transistors in weak inversion; the systems thus derived are known as logarithmic-domain (logdomain) systems. In case MOS transistors operated in saturation region are employed, the derived structures are known as Square-root domain systems. Finally, the third class of companding filters can also be obtained by employing bipolar transistors in active region or MOS transistors in weak inversion; the derived systems are known as Sinh-domain systems. During the last several years, a significant research effort has been already carried out in the area of companding circuits. This is due to the fact that their main advantages are the capability for operation in low-voltage environment and large dynamic range originated from their companding nature, electronic tunability of the frequency characteristics, absence of resistors and the potential for operations in varied frequency regions.Thus, it is obvious that companding filters can be employed for implementing high-performance analog signal processing in diverse frequency ranges. For example, companding filters could be used for realizing subsystems in: xDSL modems, disk drive read channels, biomedical electronics, Bluetooth/ZigBee applications, phaselocked loops, FM stereo demodulator, touch-tone telephone tone decoder and crossover network used in a three-way high-fidelity loudspeaker etc. A number of design methods for companding filters and their building blocks have been introduced in the literature. Most of the proposed filter structures operate either above 1.5V or under symmetrical (1.5V) power supplies. According to data that provides information about the near future of semiconductor technology, International Technology Roadmap for Semiconductors (ITRS), in 2013, the supply voltage of digital circuits in 32 nm technology will be 0.5 V. Therefore, the trend for the implementation of analog integrated circuits is the usage of low-voltage building blocks that use a single 0.5-1.5V power supply. Therefore, the present investigation was primarily concerned with the study and design of low voltage and low power Companding filters. The work includes the study about: the building blocks required in implementing low voltage and low power Companding filters; the techniques used to realize low voltage and low power Companding filters and their various areas of application. Various novel low voltage and low power Companding filter designs have been developed and studied for their characteristics to be applied in a particular portable area of application. The developed designs include the N-th order universal Companding filter designs, which have been reported first time in the open literature. Further, an endeavor has been made to design Companding filters with orthogonal tuning of performance parameters so that the designs can be simultaneously used for various features. The salient features of each of the developed circuit are described. Electronic tunability is one of the major features of all of the designs. Use of grounded capacitors and resistorless designs in all the cases makes the designs suitable for IC technology. All the designs operate in a low-voltage and low-power environment essential for portable system applications. Unless specified otherwise, all the investigations on these designs are based on the PSPICE simulations using model parameters of the NR100N bipolar transistors and BSIM 0.35μm/TSMC 0.25μm /TSMC 0.18μm CMOS process MOS transistors. The performance of each circuit has been validated by comparing the characteristics obtained using simulation with the results present in the open literature. The proposed designs could not be realized in silicon due to non-availability of foundry facility at the place of study. An effort has already been started to realize some of the designs in silicon and check their applicability in practical circuits. At the basic level, one of the proposed Companding filter designs was implemented using the commercially available transistor array ICs (LM3046N) and was found to verify the theoretical predictions obtained from the simulation results

Towards Compelling Cases for the Viability of Silicon-Nanophotonic Technology in Future Many-core Systems

Many crossbenchmarking results reported in the open literature raise optimistic expectations on the use of optical networks-on-chip (ONoCs) for high-performance and low-power on-chip communications in future Manycore Systems. However, these works ultimately fail to make a compelling case for the viability of silicon-nanophotonic technology for two fundamental reasons: (1)Lack of aggressive electrical baselines (ENoCs). (2) Inaccuracy in physical- and architecture-layer analysis of the ONoC. This thesis aims at providing the guidelines and minimum requirements so that nanophotonic emerging technology may become of practical relevance. The key enabler for this study is a cross-layer design methodology of the optical transport medium, ranging from the consideration of the predictability gap between ONoC logic schemes and their physical implementations, up to architecture-level design issues such as the network interface and its co-design requirements with the memory hierarchy. In order to increase the practical relevance of the study, we consider a consolidated electrical NoC counterpart with an optimized architecture from a performance and power viewpoint. The quality metrics of this latter are derived from synthesis and place&route on an industrial 40nm low-power technology library. Building on this methodology, we are able to provide a realistic energy efficiency comparison between ONoC and ENoC both at the level of the system interconnect and of the system as a whole, pointing out the sensitivity of the results to the maturity of the underlying silicon nanophotonic technology, and at the same time paving the way towards compelling cases for the viability of such technology in next generation many-cores systems

Fluigi: an end-to-end software workflow for microfluidic design

One goal of synthetic biology is to design and build genetic circuits in living cells for a range of applications with implications in health, materials, and sensing. Computational design methodologies allow for increased performance and reliability of these circuits. Major challenges that remain include increasing the scalability and robustness of engineered biological systems and streamlining and automating the synthetic biology workflow of “specify-design-build-test.” I summarize the advances in microfluidic technology, particularly microfluidic large scale integration, that can be used to address the challenges facing each step of the synthetic biology workflow for genetic circuits. Microfluidic technologies allow precise control over the flow of biological content within microscale devices, and thus may provide more reliable and scalable construction of synthetic biological systems. However, adoption of microfluidics for synthetic biology has been slow due to the expert knowledge and equipment needed to fabricate and control devices. I present an end-to-end workflow for a computer-aided-design (CAD) tool, Fluigi, for designing microfluidic devices and for integrating biological Boolean genetic circuits with microfluidics. The workflow starts with a ``netlist" input describing the connectivity of microfluidic device to be designed, and proceeds through placement, routing, and design rule checking in a process analogous to electronic computer aided design (CAD). The output is an image of the device for printing as a mask for photolithography or for computer numerical control (CNC) machining. I also introduced a second workflow to allocate biological circuits to microfluidic devices and to generate the valve control scheme to enable biological computation on the device. I used the CAD workflow to generate 15 designs including gradient generators, rotary pumps, and devices for housing biological circuits. I fabricated two designs, a gradient generator with CNC machining and a device for computing a biological XOR function with multilayer soft lithography, and verified their functions with dye. My efforts here show a first end-to-end demonstration of an extensible and foundational microfluidic CAD tool from design concept to fabricated device. This work provides a platform that when completed will automatically synthesize high level functional and performance specifications into fully realized microfluidic hardware, control software, and synthetic biological wetware

Design and Control of Power Converters for High Power-Quality Interface with Utility and Aviation Grids

Power electronics as a subject integrating power devices, electric and electronic circuits, control, and thermal and mechanic design, requires not only knowledge and engineering insight for each subarea, but also understanding of interface issues when incorporating these different areas into high performance converter design.Addressing these fundamental questions, the dissertation studies design and control issues in three types of power converters applied in low-frequency high-power transmission, medium-frequency converter emulated grid, and high-frequency high-density aviation grid, respectively, with the focus on discovering, understanding, and mitigating interface issues to improve power quality and converter performance, and to reduce the noise emission.For hybrid ac/dc power transmission,• Analyze the interface transformer saturation issue between ac and dc power flow under line unbalances.• Proposed both passive transformer design and active hybrid-line-impedance-conditioner to suppress this issue.For transmission line emulator,• Propose general transmission line emulation schemes with extension capability.• Analyze and actively suppress the effects of sensing/sampling bias and PWM ripple on emulation considering interfaced grid impedance.• Analyze the stability issue caused by interaction of the emulator and its interfaced impedance. A criterion that determines the stability and impedance boundary of the emulator is proposed.For aircraft battery charger,• Investigate architectures for dual-input and dual-output battery charger, and a three-level integrated topology using GaN devices is proposed to achieve high density.• Identify and analyze the mechanisms and impacts of high switching frequency, di/dt, dv/dt on sensing and power quality control; mitigate solutions are proposed.• Model and compensate the distortion due to charging transition of device junction capacitances in three-level converters.• Find the previously overlooked device junction capacitance of the nonactive devices in three-level converters, and analyze the impacts on switching loss, device stress, and current distortion. A loss calculation method is proposed using the data from the conventional double pulse tester.• Establish fundamental knowledge on performance degradation of EMI filters. The impacts and mechanisms of both inductive and capacitive coupling on different filter structures are understood. Characterization methodology including measuring, modeling, and prediction of filter insertion loss is proposed. Mitigation solutions are proposed to reduce inter-component coupling and self-parasitics

NASA Tech Briefs, October 1990

Topics: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical' Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

COBE's search for structure in the Big Bang

The launch of Cosmic Background Explorer (COBE) and the definition of Earth Observing System (EOS) are two of the major events at NASA-Goddard. The three experiments contained in COBE (Differential Microwave Radiometer (DMR), Far Infrared Absolute Spectrophotometer (FIRAS), and Diffuse Infrared Background Experiment (DIRBE)) are very important in measuring the big bang. DMR measures the isotropy of the cosmic background (direction of the radiation). FIRAS looks at the spectrum over the whole sky, searching for deviations, and DIRBE operates in the infrared part of the spectrum gathering evidence of the earliest galaxy formation. By special techniques, the radiation coming from the solar system will be distinguished from that of extragalactic origin. Unique graphics will be used to represent the temperature of the emitting material. A cosmic event will be modeled of such importance that it will affect cosmological theory for generations to come. EOS will monitor changes in the Earth's geophysics during a whole solar color cycle

Applied high resolution digital control for universal precision systems

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 223-225).This thesis describes the design and characterization of a high-resolution analog interface for dSPACE digital control systems and a high-resolution, high-speed data acquisition and control system. These designs are intended to enable higher precision digital control than currently available. The dSPACE system was previously designed within the PMC Lab and includes higher resolution A/D and D/A interfaces than natively available. Characterization on the custom A/D channel demonstrates 20.1 effective bits, or a 121 dB dynamic range, and the custom D/A channel demonstrates 15.1 effective bits, or a 91 dB dynamic range. This compares to a 15.7 effective bits on the A/D dSPACE channel and 12.3 effective bits on the D/A dSPACE channel. The increased resolution is attained by higher performance hardware and oversampling and averaging the A/D channel. The sampling rate is limited to 8 kHz. The high-resolution, high-speed data acquisition and control system can sample two A/D channels at 2.5 MHz and display/save an acquired one second burst. The A/D channel is characterized at 109 dB dynamic range with a grounded input and 96 dB dynamic range, or 0.74 nm RMS over a 50 [mu]m range, with a fixtured capacitive probe. Acquisition at 2.5 MHz and closed-loop control at 625 kHz sampling rate is implemented on a National Instruments FPGA. The A/D circuit was designed and built on a custom printed circuit board around the commercially available AD7760 sigma-delta converter from Analog Devices and includes fully differential ±10 V inputs, a dedicated microcontroller to provide an initialization sequence, and digital galvanic isolation. LabVIEW FPGA code demonstrates arbitrary transfer function control implementation.(cont.) The digital platform is applied to a 1-DOF positioner to demonstrate 0.10 nm RMS control over a 10 [mu]m mechanical range when filtered to the 1.5 kHz closed-loop bandwidth, which is limited by the A/D converter architecture propagation delay.by Aaron John Gawlik.S.M

From CoA ester supply to a yeast communication toolkit in Saccharomyces cerevisiae

Saccharomyces cerevisiae is the most widely used eukaryotic chassis in synthetic biology, as hu-manity and yeast share a long and fruitful history. For synthetic biology applications, S. cerevisiae was extensively used for metabolic engineering as well as for the construction of artificial net-works. To contribute to the metabolic engineering achievements conducted in S. cerevisiae, we extended its metabolic capacities by providing non-native short-chain acyl-coenzyme A esters as metabolic precursors. In order to advance the construction of artificial networks to multicel-lular systems we provided a comprehensive yeast communication toolkit (YCTK), and demon-strated its usability for the rapid assembly of synthetic cell-cell communication systems. Engineered production of short-chain acyl-coenzyme A esters in Saccharomyces cerevisiae Globally, S. cerevisiae is one of the most commonly used chassis organisms in modern biotech-nology and constitutes a high economic value to the growing bioecomomy. With the objective to produce novel natural products in S. cerevisiae a bottleneck of the chassis was uncovered. Short-chain acyl-coenzyme A esters serve as intermediate compounds in fatty acid biosynthesis, and are building blocks for the production of polyketides, biopolymers, and other value-added chemicals. However, S. cerevisiae’s limited repertoire of short-chain acyl-CoAs effectively pre-vents its application as a production host for a plethora of natural products. To address and re-solve this limitation, we introduced metabolic pathways to five different acyl-CoA esters into S. cerevisiae. We engineered plasmid-based yeast strains that provide propionyl-CoA, methylmalonyl-CoA, n-butyryl-CoA, isovaleryl-CoA, and n-hexanoyl-CoA. For the production of propionyl-CoA and methylmalonyl-CoA, we reestablished a published feeding-dependent pro-duction route using the PrpE and Pcc enzymes to serve as benchmark for our feeding-independent production pathways that provided in our study comparable product concentra-tions. To ensure efficient extraction of the produced metabolites we established a yeast-specific metabolite extraction protocol to determine the intracellular acyl-CoA concentrations in the engineered strains. For the production of isovaleryl-CoA, we tested two different pathways but only obtained product formation from the alternative isovaleryl-CoA biosynthetic (AIB) pathway originating from Myxococcus xanthus and obtained 5.5±1.2 µM isovaleryl-CoA. To our knowledge, this is the first reported functional heterologous expression of this pathway in S. cerevisiae. For the production of n-butyryl-CoA and n-hexanoyl-CoA, we adapted the butanol production pathway for our purposes and measured approximately 6 µM intracellular concen-tration of butyryl-CoA and hexanoyl-CoA. For the feeding-dependent pathway towards propio-nyl-CoA we obtained intracellular concentrations of 5.3 ± 2.4 µM while the feeding independ-ent 3-hydroxypropionate (3HP) pathway produced 8.5 ± 3.7 µM. The extension of both propio-nyl-CoA pathways to produce methylmalonyl-CoA resulted only into production of 0.5 ± 0.1 µM and 0.3 ± 0.3 µM methylmalonyl-CoA. Not only but particularly for the production of methylmalonyl-CoA further optimization is required. To allow rapid pathway prototyping, op-timization and testing of alternative enzymes, we established a short-chain acyl-CoA Golden Gate collection. This collection enables together with the well-known Dueber yeast toolkit YTK collection the examination of different enzymes variants and to investigate optimized expres-sion of the corresponding genes. We conclude that the acyl-CoAs produced here, that are common building blocks of secondary metabolites, prepared the ground for prospective engineered production of a variety of natural products in S. cerevisiae. These acyl-CoA producing strains together with the short-chain acyl-CoA collection lay the foundation to further explore S. cerevisiae as a heterologous production host for high-value secondary metabolite production. Yeast communication toolkit The construction of multicellular networks was a proposed aim already early on in synthetic biology. Today, they still hold many promises like the division of labor or the performance of more complex tasks. Most of the systems so far were implemented in bacterial chassis and only a few examples exist for the eukaryotic chassis S. cerevisiae. Especially for gram-negative bacterial chassis, the quorum sensing system provides a large diversity of ready to use communication systems. Also, yeast species evolved a communication system using peptide-based pheromones to interact with the opposite mating type. Here, we employed the natural diversity of the pep-tide α-factor pheromones, the corresponding GPCR receptors, as well as of barrier proteases, that function similarly to quorum quenching enzymes. With the establishment of the Golden Gate yeast communication toolkit (YCTK) we provide a standardized collection of parts that al-low the rapid construction of multicellular networks in the model organism S. cerevisiae. The feasible designs are limitless as well as the number of envisioned applications. The YCTK collec-tion consists of responder (pheromone-responsive promoters), sender (mfα1 genes – α-factors), receiver (Ste2 receptors) and barrier (Bar1 proteases) parts. We characterized the dynamics of the pheromone-inducible promoters in the different mating-type strain backgrounds and de-termined the dose-response to the α-factor as well as their temporal response. The different promoters exhibited a range of different dynamics and properties that enable the implementa-tion of different prospective network design motives. The characterization results of the Ste2 receptors indicated that our collection is comprised of receptors with high α-factor promiscuity and of receptors with high substrate specificity for their cognate α-factor. Further we found that different Ste2 receptors exhibit different sensitivities towards the cognate as well as to non-cognate α-factors. The promiscuity of the Ste2 receptors did not correlate with the α-factor se-quences. Our likelihood analysis of the Ste2 receptors indicated that the ones closer related to S. cerevisiae tend to be stimulated by the α-factors of related species. Our likelihood analysis of the Ste2 receptors coincided with the phylogenetic relationships of the species. Interesting is also the finding that α-factors of species for which the receptor exhibited high α-factor promis-cuity stimulated only a few receptors. Even though only five of the selected barrier proteases were functionally expressed the characterization of the protease promiscuity was to our knowledge the most comprehensive study of its kind so far. Similar to the receptors we identi-fied promiscuous and substrate specific barrier proteases. The proposed model of a coevolution between the receptor and barrier proteases to recognize similar sequence motives of the α-factor was partly validated, however, the model is not universally applicable according to our results. The extended knowledge of the pheromone-inducible promoters, the crosstalk be-tween α-factors, receptors and barrier proteases, and an initial tunability test enabled proof of principle construction of multicellular systems using the YTCK collection. We engineered mul-ticellular logic gate-like population networks that allow the receiver cells to conditionally re-spond to the population composition. While the α-factor signaling motif is functional and was used to successfully establish OR and AND gate-like systems, signal disruption by a barrier pro-tease of a self-stimulating or a signaling motif requires further optimization. Overall, the reali-zation of multicellular networks using the YCTK was proven to be successful. To summarize, with the YCTK we provide a set of comprehensively characterized sender, re-ceiver, and barrier parts to facilitate the implementation of cell-cell and thus multicellular communication networks in S. cerevisiae