Analog Implementation of Fractional-Order Elements and Their Applications

With advancements in the theory of fractional calculus and also with widespread engineering application of fractional-order systems, analog implementation of fractional-order integrators and differentiators have received considerable attention. This is due to the fact that this powerful mathematical tool allows us to describe and model a real-world phenomenon more accurately than via classical “integer” methods. Moreover, their additional degree of freedom allows researchers to design accurate and more robust systems that would be impractical or impossible to implement with conventional capacitors. Throughout this thesis, a wide range of problems associated with analog circuit design of fractional-order systems are covered: passive component optimization of resistive-capacitive and resistive-inductive type fractional-order elements, realization of active fractional-order capacitors (FOCs), analog implementation of fractional-order integrators, robust fractional-order proportional-integral control design, investigation of different materials for FOC fabrication having ultra-wide frequency band, low phase error, possible low- and high-frequency realization of fractional-order oscillators in analog domain, mathematical and experimental study of solid-state FOCs in series-, parallel- and interconnected circuit networks. Consequently, the proposed approaches in this thesis are important considerations in beyond the future studies of fractional dynamic systems

NASA Tech Briefs Index, 1977, volume 2, numbers 1-4

Announcements of new technology derived from the research and development activities of NASA are presented. Abstracts, and indexes for subject, personal author, originating center, and Tech Brief number are presented for 1977

Advances in Solid State Circuit Technologies

This book brings together contributions from experts in the fields to describe the current status of important topics in solid-state circuit technologies. It consists of 20 chapters which are grouped under the following categories: general information, circuits and devices, materials, and characterization techniques. These chapters have been written by renowned experts in the respective fields making this book valuable to the integrated circuits and materials science communities. It is intended for a diverse readership including electrical engineers and material scientists in the industry and academic institutions. Readers will be able to familiarize themselves with the latest technologies in the various fields

Theory, Modelling and Implementation of Graphene Field-Effect Transistor

PhDTwo-dimensional materials with atomic thickness have attracted a lot of attention from researchers worldwide due to their excellent electronic and optical properties. As the silicon technology is approaching its limit, graphene with ultrahigh carrier mobility and ultralow resistivity shows the potential as channel material for novel high speed transistor beyond silicon. This thesis summarises my Ph.D. work including the theory and modelling of graphene field-effect transistors (GFETs) as well as their potential RF applications. The introduction and review of existing graphene transistors are presented. Multiscale modelling approaches for graphene devices are also introduced. A novel analytical GFET model based on the drift-diffusion transport theory is then developed for RF/microwave circuit analysis. Since the electrons and holes have different mobility variations against the channel potential in graphene, the ambipolar GFET cannot be modelled with constant carrier mobility. A new carrier mobility function, which enables the accurate modelling of the ambipolar property of GFET, is hence developed for this purpose. The new model takes into account the carrier mobility variation against the bias voltage as well as the mobility difference between electrons and holes. It is proved to be more accurate for the DC current calculation. The model has been written in Verilog-A language and can be import into commercial software such as Keysight ADS for circuit simulation. In addition, based on the proposed model two GFET non-Foster circuits (NFCs) are conducted. As a negative impedance element, NFCs find their applications in impedance matching of electrically small antennas and bandwidth improvement of metasurfaces. One of the NFCs studied in this thesis is based on the Linvill's technique in which a pair of identical GFETs is used while the other circuit utilises the negative resistance of a single GFET. The stability analysis of NFCs is also presented. Finally, a high impedance surface loaded with proposed NFCs is also studied, demonstrating significant bandwidth enhancement.Engineering and Physical Sciences Research Council (EPSRC) Grant on `Graphene Flexible Electronics and Optoelectronics' (EP/K01711X/1), the EU Graphene Flagship (FP7-ICT-604391) and Graphene Core 1 (H2020 696656

Integrated RF oscillators and LO signal generation circuits

This thesis deals with fully integrated LC oscillators and local oscillator (LO) signal generation circuits. In communication systems a good-quality LO signal for up- and down-conversion in transmitters is needed. The LO signal needs to span the required frequency range and have good frequency stability and low phase noise. Furthermore, most modern systems require accurate quadrature (IQ) LO signals. This thesis tackles these challenges by presenting a detailed study of LC oscillators, monolithic elements for good-quality LC resonators, and circuits for IQ-signal generation and for frequency conversion, as well as many experimental circuits. Monolithic coils and variable capacitors are essential, and this thesis deals with good structures of these devices and their proper modeling. As experimental test devices, over forty monolithic inductors and thirty varactors have been implemented, measured and modeled. Actively synthesized reactive elements were studied as replacements for these passive devices. At first glance these circuits show promising characteristics, but closer noise and nonlinearity analysis reveals that these circuits suffer from high noise levels and a small dynamic range. Nine circuit implementations with various actively synthesized variable capacitors were done. Quadrature signal generation can be performed with three different methods, and these are analyzed in the thesis. Frequency conversion circuits are used for alleviating coupling problems or to expand the number of frequency bands covered. The thesis includes an analysis of single-sideband mixing, frequency dividers, and frequency multipliers, which are used to perform the four basic arithmetical operations for the frequency tone. Two design cases are presented. The first one is a single-sideband mixing method for the generation of WiMedia UWB LO-signals, and the second one is a frequency conversion unit for a digital period synthesizer. The last part of the thesis presents five research projects. In the first one a temperature-compensated GaAs MESFET VCO was developed. The second one deals with circuit and device development for an experimental-level BiCMOS process. A cable-modem RF tuner IC using a SiGe process was developed in the third project, and a CMOS flip-chip VCO module in the fourth one. Finally, two frequency synthesizers for UWB radios are presented

High performance continuous-time filters for information transfer systems

Vast attention has been paid to active continuous-time filters over the years. Thus as the cheap, readily available integrated circuit OpAmps replaced their discrete circuit versions, it became feasible to consider active-RC filter circuits using large numbers of OpAmps. Similarly the development of integrated operational transconductance amplifier (OTA) led to new filter configurations. This gave rise to OTA-C filters, using only active devices and capacitors, making it more suitable for integration. The demands on filter circuits have become ever more stringent as the world of electronics and communications has advanced. In addition, the continuing increase in the operating frequencies of modern circuits and systems increases the need for active filters that can perform at these higher frequencies; an area where the LC active filter emerges. What mainly limits the performance of an analog circuit are the non-idealities of the used building blocks and the circuit architecture. This research concentrates on the design issues of high frequency continuous-time integrated filters. Several novel circuit building blocks are introduced. A novel pseudo-differential fully balanced fully symmetric CMOS OTA architecture with inherent common-mode detection is proposed. Through judicious arrangement, the common-mode feedback circuit can be economically implemented. On the level of system architectures, a novel filter low-voltage 4th order RF bandpass filter structure based on emulation of two magnetically coupled resonators is presented. A unique feature of the proposed architecture is using electric coupling to emulate the effect of the coupled-inductors, thus providing bandwidth tuning with small passband ripple. As part of a direct conversion dual-mode 802.11b/Bluetooth receiver, a BiCMOS 5th order low-pass channel selection filter is designed. The filter operated from a single 2.5V supply and achieves a 76dB of out-of-band SFDR. A digital automatic tuning system is also implemented to account for process and temperature variations. As part of a Bluetooth transmitter, a low-power quadrature direct digital frequency synthesizer (DDFS) is presented. Piecewise linear approximation is used to avoid using a ROM look-up table to store the sine values in a conventional DDFS. Significant saving in power consumption, due to the elimination of the ROM, renders the design more suitable for portable wireless communication applications

An investigation of the microwave upset of avionic circuitry

Circuit technology of the 1970-90 era appears fairly resilient to microwave radio frequency interference, with few reported occurrences of interference. However, a proposition has been developed which substantiates fears that new technologies, with their extremely high packing densities, small device p-n junctions and very high clock rates, will be very susceptible to interference throughout the microwave band It has been postulated that the mechanism for this upset is demodulation and that it will come about by either the predicted changes in the microwave RF environment by the year 2000, or by a suitable choice of phasing and frequency at high power. The postulation is studied by developing an overall ingress equation, relating incident power density at the aircraft to the load voltage at an avionic circuit component. The equation's terms are investigated to quantif' their contribution to the likelihood of interference. The operational RF environment for aircraft is studied and predictions of the current and maximum future environments are made. A practical investigation of 2-18 GH.z airframe shielding is described, with comparison of the results with those from a number of other aircraft and helicopter types. A study of ingress into avionic boxes is presented and is followed by the results of an investigation of energy coupling via the cables and connectors, including the development and practical examination of a coupling model based on transmission line theory. A study is then presented of circuit technology developments, electronic component interference and damage mechanisms, and evidence of upset of electronic equipment is given. Investigations show that there is more 1-18 GHz upset of electronic equipment than originally thought and data suggest that thermal damage of active devices may dominate over-voltage stressing of p-n junctions. Aircraft investigations have shown that incident microwave radiation is attenuated approximately 20 dB by the airframe, in a complex fashion which does not lend itself to being modelled easily. Under some conditions this value of airframe attenuation is seen to approach zero, removing any shielding of avionics by the airframe for these cases. A predictor for airframe shielding independent of air vehicle type has been developed, based on cumulative density ftrnctions of all data from each of the aircraft types examined. The cable coupling model gives good agreement with measured data except for the dependency of load voltage on cable length and illuminating antenna position along the cable, for which an empirical equation has been developed. Computer power limitations and significant variations of most of the parameters in the overall ingress equation suggest that modelling of the complex innards of aircraft and avionics at these frequencies will remain impractical for the foreseeable future and that probabilistic models are the only achievable goal. It is concluded that all avionic circuit technologies may well be upset as postulated above or by speculative High Power Microwave weapons, but that careful use of existing aircraft and equipment design methodologies can offer adequate protection. An improved protection regime is proposed for future aircraft and a number of fUture research areas are identified to enable better understanding of the microwave hazard to aircraft. The three areas which will add most to this understanding are modelling of the precise microwave environment to be encountered, further airframe shielding measurements and analyses, from all incidence angles and on different aircraft types, and the construction and cumulative probability fUnction analyses of electronic component and equipment upset databases

VLSI Design

This book provides some recent advances in design nanometer VLSI chips. The selected topics try to present some open problems and challenges with important topics ranging from design tools, new post-silicon devices, GPU-based parallel computing, emerging 3D integration, and antenna design. The book consists of two parts, with chapters such as: VLSI design for multi-sensor smart systems on a chip, Three-dimensional integrated circuits design for thousand-core processors, Parallel symbolic analysis of large analog circuits on GPU platforms, Algorithms for CAD tools VLSI design, A multilevel memetic algorithm for large SAT-encoded problems, etc