Computer-aided Circuit Design Research Articles

Look-up table based I-V model for GaN HEMT devices for Microwave Applications

In this work, a newly found innovative interposable lookup table based nonlinear empirical DC I-V model for GaN HEMT device has been formulated. Angelov and Yang's models have been taken as reference models to study the effects of bias (Vgs, Vds) dependent traps (gate lag and drain lag), self-healing, virtual gate formation, etc. on I-V characteristics functions and their inclusion into I-V equation functions of the proposed model. A new polynomial ratio function of Vds with its coefficients varying with Vgs has been formulated as a first function of the I-V model equation, to describe the transfer characteristics of the GaN HEMT. The obtained coefficients of the polynomial ratio function have been calculated by the curve fitting tool, are used to form a look-up table so that the I-V model is fast and accurate. Model verification has been done using 8 × 75 µm gate periphery and 0.25 µm gate length GaN HEMT of UMS foundry. The measured and modeled results of I-V characteristics as well as transfer characteristics are compared and found to be matched accurately with each other. Because of this, this model is more accurate and proficient in the representation of GaN HEMT I-V characteristics when compared to the Angelov DC I-V model. The proposed methodology can be used to model all GaN HEMT devices.Using the proposed nonlinear I-V equation, an empirical model has been generated in AWR MWO using an interpolable lookup table of coefficients varying with Vgs for the GaN HEMT of UMS, CREE and WIN foundry, which can be used for Computer-Aided Design (CAD) of RF circuits, etc.

A Parallel Approach to Perform Threshold Value and Propagation Delay Analyses of Genetic Logic Circuit Models.

Experiments with synthetic genetic logic circuits can be time-consuming and expensive. Accordingly, advances in the field of computer-aided design and simulation of genetic circuits have reduced the cost and time required for experimentation. D-VASim is the first genetic circuit simulation tool that allows users to interact with the model during run-time. In contrast to electronic circuits, genetic circuits have different threshold values for different circuits, which need to be estimated prior to simulation. D-VASim allows the user to perform threshold concentration and propagation delay analysis before simulating the circuit. The algorithm currently used in D-VASim has considerable scope for improvements. Thus, we propose a parallel implementation of the algorithm, significantly faster by up to 16 times. In adddition, we improve the algorithm for consistent runtimes across multiple simulation runs under the same parameter settings, reducing the worst-case standard deviation in runtime from 6.637 to 1.841. Our algorithm also estimates the threshold value more accurately, as evident from experimentation for long runtimes. With these modifications, the utility of D-VASim as a virtual laboratory environment has been significantly enhanced.

A Compact Gated-Synapse Model for Neuromorphic Circuits

This work reports a compact behavioral model for gated-synaptic memory. The model is developed in Verilog-A for easy integration into computer-aided design of neuromorphic circuits using emerging memory. The model encompasses various forms of gated synapses within a single framework and is not restricted to only a single type. The behavioral theory of the model is described in detail along with a full list of the default parameter settings. The model includes parameters, such as a device's ideal set time, threshold voltage, general evolution of the conductance with respect to time, decay of the device's state, etc. Finally, the model's validity is shown via extensive simulation and fitting to experimentally reported data on published gated-synapses.

Design Database of Cad System as the Basis of the Digital Twin of the Automation System of Power Plants and Substations

The principles of the formation and use of the “digital twin” of a digital substation automation system based on the design database developed as part of a computer-aided design of secondary switching circuits (CAD CVC) are considered. A description of the design database structure and the information model, that provides integrated work both with circuit diagrams and installation documentation, and with digital exchange models in accordance with IEC 61850, is given. Auser interface for searching information is presented. It is proposed to use the “digital twin” at all stages of the object’s life cycle: design, installation, commissioning, and operation.

Exploiting Errors for Efficiency

When a computational task tolerates a relaxation of its specification or when an algorithm tolerates the effects of noise in its execution, hardware, system software, and programming language compilers or their runtime systems can trade deviations from correct behavior for lower resource usage. We present, for the first time, a synthesis of research results on computing systems that only make as many errors as their end-to-end applications can tolerate. The results span the disciplines of computer-aided design of circuits, digital system design, computer architecture, programming languages, operating systems, and information theory. Rather than over-provisioning the resources controlled by each of these layers of abstraction to avoid errors, it can be more efficient to exploit the masking of errors occurring at one layer and thereby prevent those errors from propagating to a higher layer. We demonstrate the potential benefits of end-to-end approaches using two illustrative examples. We introduce a formalization of terminology that allows us to present a coherent view across the techniques traditionally used by different research communities in their individual layer of focus. Using this formalization, we survey tradeoffs for individual layers of computing systems at the circuit, architecture, operating system, and programming language levels as well as fundamental information-theoretic limits to tradeoffs between resource usage and correctness.

Grammatical Evolution-based Analog Circuit Synthesis

Computer aided circuit design is becoming one of the mainstream methods for helping circuit designers. Multiple new methods have been developed in this field including Evolutionary Electronics. A lot of work has been done in this field but there is still a room for improvement since some of the solutions lack the flexibility (diversity of components, limited topology etc.) in circuit design or lack complex fitness functions that would enable the synthesis of more complex circuits. The research presented in this article aims to improve this by introducing Grammatical Evolution-based approach for circuit synthesis. Grammatical Evolution offers great flexibility since it is rule based – adding a new element is as simple as writing one additional line of initialization code. In addition, the use of a complex multi-criteria function allows us to create circuits that can be as complex as required thus further increasing the flexibility of the approach. To achieve this, we use a combination of Python and SPICE to create a series of netlists, evaluate them in the PyOpus environment, and select the best possible circuit for the task. We demonstrate the efficiency of our approach in three different case studies where we automatically generate oscillators and high/low-pass filters of second and third order.

NANODEVICES WITH PROGRAMMABLE LOGIC

The paper describes the computer-aided design of nanoelectronic circuits with programmable logic on quantum majority components is implemented. The single-electronic component base has the greatest influence on such basic parameters of modern computer systems as performance exceeding 10 THz, power consumption less than 1 nW and submicron dimensions. Methods of constructing arithmeticological computing devices of combinational and sequential types, which realize almost complete system of logical functions both in majority and in Boolean bases, are offered. The design of reliable nanoelectronic circuits with programmable logic based on the technology of quantum automata has been described. While constructing majority circuits the interaction of Colomb forces using. The order of syntesis and programming of various types of arithmetic-logic nanodevices has been analyzed.

A novel empirical I-V model for GaN HEMTs

In this paper, a novel eight-parameter empirical nonlinear current-voltage (I-V) model for gallium nitride (GaN) high electron mobility transistors (HEMTs) is presented. A hyperbolic sine function is introduced in this model to describe the transfer characteristics between drain-source current, Ids, and gate-source voltage, Vgs. The self-heating and trapping effects have been considered and incorporated into the proposed model through expansion parameters. The proposed model has been verified on four different types of GaN HEMTs with good agreements between the simulated curves and the measured data. Comparison between the proposed model and other traditional non-square-law models indicates a significant accuracy improvement especially in linear region by the proposed model. This simple but accurate empirical I-V model can be easily implemented for computer aided circuit design and simulation with GaN HEMTs.

Analysis and Compact Modeling of Magnetic Tunnel Junctions Utilizing Voltage-Controlled Magnetic Anisotropy

A macrospin compact model of a perpendicularly magnetized voltage-controlled magnetic tunnel junction (MTJ) is introduced, for the evaluation of electronic and magnetic characteristics associated with its switching behavior. The voltage-driven precessional switching has been shown to outperform current-driven switching in terms of energy, speed, and bit density. However, to realize the device in embedded system memory applications, developing a compact model for simulating hybrid MTJ/CMOS circuits is necessary. This framework also needs to be compatible with conventional computer-aided circuit design tools and flows. In this paper, the voltage-controlled magnetic anisotropy effect is included as a component of the effective magnetic field in a Landau–Lifshitz–Gilbert (LLG) equation-based model. The compact model is described by Verilog-A, providing a numerical solution for a 3-D magnetization trajectory and the corresponding conductance change of the MTJ. We also include the thermal noise effect in the LLG equation to allow the evaluation of stochastic switching behavior under a wide variety of bias conditions, which can be quantified in terms of write error rate (WER). It is shown that the model allows for optimization of write pulse shape and design considerations to achieve the lowest WER for given MTJ parameters.

The Resonant Tunneling Diode characterization for high frequency communication systems

In this paper, a detailed derivation process is proposed to characterize the Resonant Tunneling Diode (RTD) for high frequency regime. The proposed model is used to design and analyze a simple microwave oscillator based on the RTD using the commercial circuit simulation software, ADS from Agilent Technologies. The simulation is carried out using different equivalent circuit models; the proposed model, the original constant RC model, and the series/parallel double RC model, which is an alternative to the quantum-inductance RLC model. This is performed in terms of oscillation frequency and output power against resonant circuit elements, considering the CPU time. A comparison between the simulation results of the three models indicates that the proposed model is simple, accurate, and appropriate to investigate the behavior of the RTD at high frequency without any singularity and convergence problems. Also, its complexity (CPU time) is less than that of the series/parallel double RC model and higher than that of constant RC model. However, the constant RC model is inaccurate, especially in high frequency regime. In addition, the proposed technique can be easily incorporated into computer aided circuit design software, such as SPICE and ADS software, to simulate circuits containing RTD in high frequency regime. In brief, this work adds important contributions to the accurate characterization and modeling of RTDs and analyzes its based circuits in high frequency regime by addressing the problems of the current RTD equivalent circuit models.

Computer-aided design of resistance micro-fluidic circuits for 3D printing

Microfluidic circuits, a sub class of lab-on-a-chip systems, are rapidly expanding into biological, chemical and physical research. Resistance microfluidic circuits are particularly useful for precise control of tempo-spatial conditions at a Nano-liter scale. The current design process of resistance microfluidic circuits starts with system specifications and concludes with a geometric realization of a topological graph that describes a 2-dimensional network of mechanical micro-scale channels. This design paradigm often relies on manual design and drawing. Moreover, since fabrication of microfluidic circuits is dominantly based on soft-lithography, the design-to-production transition often requires manual intervention. In this work, we present an automatic design process for resistance microfluidic circuits that outputs a fabrication-ready circuit model following a given set of specifications. We exploit the hydraulic–electric circuit analogy to define an abstract specification of microfluidic circuits. Based on this abstract specification, we defined an algorithm that uses fabrication-related constraint propagation and an optimization protocol to suggest a spatially optimized design for the proposed circuit. Finally, we automatically generate a vector-graphics model for 3D printing. Our approach can significantly reduce the design time of resistance microfluidic circuits, allowing a seamless computer-aided transition from concept to production.

Analytical and electrical modeling of a MEMS thermoelectric microwave power sensor

A new analytical method which can support full computer-aided circuit design for a microelectromechanical (MEMS) thermoelectric microwave power sensor operable at X-band is presented in this paper. A reduced dimensional form of a heat transfer equation is built in the radial direction based on point heat source approximation and precise volume mesh of the sensor. Frequency dependent losses are discussed to explain the sensitivity degradation with frequency. Based on this analysis, an electrical model for the power sensor is established. This approach facilitates the modeling of the coupled energy domains in the power sensor straightforwardly by means of a computer-aided simulation. Better estimation property is obtained compared to our previous works. Verifications are both conducted through ANSYS simulation and measurements with close agreements are observed. Relative errors between them are smaller than 13%. The deviations are discussed in detail. Fabrication of the thermoelectric power sensor is based on MEMS technology and the GaAs MMIC process.

Influences of Electric Parameters of Pulsed Power Supply on Electromagnetic Railgun System

To analyze the electric parameters of a pulsed power supply (PPS) system and their influence on muzzle velocity, a stable and reliable 200-kJ compact PPS system used for electromagnetic railgun system has been developed. The PPS system consists of ten modules, and each module is comprised of a high energy density capacitor (3270 $\mu $ F/3.5 kV), 4-in thyristor, a pulse shaping inductor (1.5 $\mu $ H), and a crowbar diode. At the same time, a railgun circuit model for simulation was established. In this model, velocity skin effect, current skin effect, and friction were taken into consideration. Some electromagnetic launching experiments were carried out to verify the correctness of the railgun circuit model. Influence of different electric parameters of PPS on muzzle velocity was analyzed by the computer aided circuit design program PSPICE based on this model. The parameters include capacitance, equivalent series resistance (ESR) of the capacitor, inductance, and jitter time of the thyristor. The simulation results show that the ESR is the most critical influencing factor (the deviation of velocity is −4.286% when the ESR is 5 m $\Omega $ ). The following is the change of the capacitance (the deviation of velocity is −3.827% when the capacitance decreases to 95%C0). In the meantime, the changes of the resistance of inductor do have an influence on muzzle velocity (the deviation of velocity is −0.908% when the resistance of inductor is 1 m $\Omega $ ). However, the changes of inductance and the jitter time of the thyristor impose no significant effect on muzzle velocity. The conclusions provide reference to the overall optimization of PPS design and quality control of the manufacturing process.

A Microstrip Circuit Tool Kit App with FDTD Analysis Including Lumped Elements

At the 2014 IEEE Microwave Theory and Techniques Society (MTT-S) International Microwave Symposium (IMS2014), the Apps for MTT Student Design Contest was held,sponsored by the Microwave Field Theory (MTT-15) Technical Committee. One objective of the design contest is to take advantage of the growing computing capacity of smart handheld and mobile devices to promote their use for the computer-aided analysis and design of microwave components and circuits. With the rapid development of recent iOS and Android smart phones or pads, some advanced scientific computation programs can now be executed on these portable devices. These handy devices can also deal with microwave circuit calculations if the applications (apps) are well designed. Since these devices are always accessible, it may be more convenient for engineers and students to analyze and design microwave circuits on the phones or pads directly. Note that full-wave, three-dimensional (3-D) simulations for complicated microwave circuits usually require a large amount of memory and a central processing unit with high performance, so it may be difficult to run full-wave 3-D simulations on portable smart devices.

FAST: A Framework for Simulation and Analysis of Large-Scale Protein-Silicon Biosensor Circuits

This paper presents a computer aided design (CAD) framework for verification and reliability analysis of protein-silicon hybrid circuits used in biosensors. It is envisioned that similar to integrated circuit (IC) CAD design tools, the proposed framework will be useful for system level optimization of biosensors and for discovery of new sensing modalities without resorting to laborious fabrication and experimental procedures. The framework referred to as FAST analyzes protein-based circuits by solving inverse problems involving stochastic functional elements that admit non-linear relationships between different circuit variables. In this regard, FAST uses a factor-graph netlist as a user interface and solving the inverse problem entails passing messages/signals between the internal nodes of the netlist. Stochastic analysis techniques like density evolution are used to understand the dynamics of the circuit and estimate the reliability of the solution. As an example, we present a complete design flow using FAST for synthesis, analysis and verification of our previously reported conductometric immunoassay that uses antibody-based circuits to implement forward error-correction (FEC).

Computational methods in synthetic biology: towards computer-aided part design

A number of computational tools have been developed for composing synthetic gene circuits, managing workflows, and simulating their behavior. Less attention has been directed towards the underlying parts that go into these designs. New computational approaches nonetheless are being developed for engineering these parts and relating their underlying DNA or amino-acid sequences to functional parameters. These approaches range from detailed mechanistic models to simple ones based on statistical correlations. The challenges will be to integrate the disparate tools into a common framework for the computer-aided design of synthetic gene circuits.

Model-Driven Engineering of RNA Devices to Quantitatively Program Gene Expression

The models and simulation tools available to design functionally complex synthetic biological devices are very limited. We formulated a design-driven approach that used mechanistic modeling and kinetic RNA folding simulations to engineer RNA-regulated genetic devices that control gene expression. Ribozyme and metabolite-controlled, aptazyme-regulated expression devices with quantitatively predictable functions were assembled from components characterized in vitro, in vivo, and in silico. The models and design strategy were verified by constructing 28 Escherichia coli expression devices that gave excellent quantitative agreement between the predicted and measured gene expression levels (r = 0.94). These technologies were applied to engineer RNA-regulated controls in metabolic pathways. More broadly, we provide a framework for studying RNA functions and illustrate the potential for the use of biochemical and biophysical modeling to develop biological design methods.

(Invited) Integrated Photodetectors in CMOS Chips and their Spectral Sensitivity

Diodes inherent in a CMOS process are light sensitive and could be exploited as photodetectors. To detect light the photo generated carriers need to be separated by the electrical field of an internal pn junction. They are either generated inside the depletion region or can get there by diffusion. The depth where these carriers are generated depends strongly on the wavelength. The generation profile, the pn junction depth and the diffusion length all impact the spectral sensitivity. A simple model is presented to describe these dependencies. It has enabled spectral response to be optimized within physical limits. Furthermore, a special diode was built and integrated which achieved more than 90% efficiency in the demanding blue corner of the visible spectrum. As the analytical description is based on only 5 parameters it can be incorporated in a behavioral diode model to support computer aided circuit design.

A Historical Review of Circuit Simulation

Within the Circuits and Systems (CAS) Society, developments in computer-aided circuit analysis and circuit design commenced in the early 1950's using the earliest digital computers. Initially, computer-aided circuit analysis of linear circuits was used in design optimization, design centering, and in determining the effects of parasitics on circuit performance. Although this use of computer-aided circuit analysis has continued, computer-aided design (CAD) and circuit design automation within the CAS Society are now principally concerned with problems associated with the overall design and evaluation of very large circuits and systems.

Study of the methods of calibration of the process OPC VT-5 models with a variable threshold

One of the most widely used approaches to simulation of complex lithographic systems is considered. The approach makes it possible to take into account the effect of the features of the manufacturing process on the transfer of very large-scale integration (VLSI) topology to a silicon wafer. The approach is based on the present-day aids for simulation and computer-aided design (CAD) of VLSI circuits and provides a means for reducing errors (that arise from the imperfection of the manufacturing process) in transferring the design onto the silicon wafer. A family of empirical VT-5 mathematical models involving a variable threshold is analyzed. The models are used in the CAD Calibre, Mentor Graphics Ltd. The results of calibration and verification of the process model for a polysilicon layer produced by the technology of Department of Microtechnology (DMT), Scientific Research Institute of System Analysis, Russian Academy of Sciences, in compliance with the 0.25 μm design standards are reported. The results of verification of the developed model over the contours of complex topological structures are reported. The verification was conducted with the use of the SEMCal module of the CAD Calibre.