Computer-aided transistor design, characterization, and optimization

A systematic and general method of computing ac and dc characteristics of double-diffused junction transistors using major process parameters such as dimensions of the device, surface concentration, junction depth, diffusion time, temperature, and diffusion coefficient as a function of temperature and impurity concentration is described. These parameters can be checked during the process and, therefore, can aid the process control problem by predicting the expected values of junction depth and sheet resistivity. If the specified control parameters are met during the fabrication, the ac and dc characteristics of the device will be realized. The time and/or frequency response of a circuit can be computed using the ac and dc characteristics of the diffused devices of the circuit on the basis of a distributed or an equivalent lumped model. The measurement of important ac parameters on the basis of these models has also been simulated on the computer, thus aiding the characterization problem of the device in the integrated circuit environment. Also, the switching speed of a loaded logic net can be computed and optimized by trading off interacting parameters and relating them back to the original diffusion process parameters and dimensions of the components. Finally, experimental verification of the computed results has been accomplished and found to be satisfactory.     

COMPUTER-AIDED OPTIMIZATION DESIGN OF BANDPASS FILTER WITH DIELECTRIC RESONATORS

By way of employing a multimode method together with the multimode transmission matrixtechnique based on the theory of planar circuits, the paper presents computer-aided design and optimized de-sign of bandpass fllters with dielectric resonators, and their sample was tested. The experimental result ofthe sample shows a reasonable agreement with the designed one.     

Computer-aided design and optimization of a broad-band high-frequency monolithic amplifier

A monolithic wide-band amplifier for applications in counters from dc to UHF frequencies has been realized. The use of computer-aided design techniques, using a transistor model, and a broad-band feedback configuration has resulted in a monolithic amplifier that previously could only be constructed in hybrid form. This paper describes the development of a new high-frequency transistor model and a dc-coupled monolithic high-frequency amplifier that incorporates a final masking step option to obtain a maximally flat response over a 700-MHz bandwidth.     

Computer-aided design

The November issue of the Proceedings of the IEEE will be a special issue on computer-aided design, consisting of many papers on specialized aspects of this growing field. To put the new development in proper perspective, this article examines just what it is that justifies all the excitement. It discusses the nature of the engineering design process, man-computer systems, both passive and active computer graphics, nongraphic applications, and problems of computer technology, and points out for engineers the importance of computer-aided design for the future.     

Analysis and design of a new type NRD-guide E-plane Y-junction circulator

A new type of E-plane Y-junction circulator has been developed based on the nonradiative dielectric waveguide (NRD-guide) in Ka- band. First, the circulation principle has been analysed by the theory of polarization wave. The field components in the nonreciprocal Y-junction zone and the conclusion of 60° phase difference between clockwise and counterclockwise rotating polarization modes has been obtained. And then, the resonant frequency of the non-dc biased triangle ferrite sample has also been calculated. This kind of structure is benefit to enlarge the bandwidth of the Y-junction circulator. As an example, we had designed and fabricated a circulator in Ka-band. Its operating frequency is 35. 1GHz, the 1.5dB insertion loss and 20dB isolation bandwidth is about 1. 0GHz.     

Computer-aided photonics design

Photonics-the technology of using particles of light as carriers of information-is catching on because of the advantages of optical fiber over copper cable for data transmission, and the use of optoelectronic techniques for sensing and instrumentation. Here, the author describes how powerful laser models in photonics system simulators are a vital step toward virtual optical benches for optimizing such communication system design     

Computer-aided network optimization the state-of-the-art

Formal optimization procedures are destined to assume an increasingly useful role in network design. To form a basis for continued development, this paper summarizes the field by 1) presenting an extensive and detailed review of the optimization methods used in computer-aided network design and 2) giving state-of-the-art examples of iterative network design.     

Ultra-wide-band NRD-guide Antenna

A new ultra-wide-band(UWB) horn antenna based on the nonradiative dielectric waveguide (NRD-guide) was proposed to solve the problem of UWB antennas, TEM horns for example, generally suffer from large side leakage. The rule of the theoretical selection of its parameters, if NRD-guide is used as the UWB antennas, is studied firstly, then the radiation characteristics for an open-ended NRD-guide are calculated by FDTD (finite-difference time-domain) method.     

Computer-aided design of FIR filters

A computer-aided technique for designing FIR digital filters with close to linear phase property is presented. The approach is based on a constrained optimisation problem designed to minimise the mean-square error between a desired response and the filter response over a passband of interest subject to a mean-square stopband constraint. Numerical results are presented to illustrate the performance achievable.<>     

Computer-aided design of VLSI circuits

With the rapid evolution of integrated circuit (IC) technology to larger and more complex circuits, new approaches are needed for the design and verification of these very-large-scale integrated (VLSI) circuits. A large number of design methods are currently in use. However, the evolution of these computer aids has occurred in an ad hoc manner. In most cases, computer programs have been written to solve specific problems as they have exist and no truly integrated computer-aided desisn (CAD) systems exist for the design of IC's. A structured approach both to circuit desisn and to circuit verification, as well as the development of integrated design systems, is necessary to produce cost-effective error-free VLSI circuits. This paper presents a review of the CAD techniques which have been used in the design of IC's, as well as a number of design methods to which the application of computer aids has proven most successful. The successful application of design-aids to VLSI circuits requites an evolution from these techniques and design methods.     

Computer-aided design of analog and mixed-signal integratedcircuits

This survey presents an overview of recent advances in the state of the art for computer-aided design (CAD) tools for analog and mixed-signal integrated circuits (ICs). Analog blocks typically constitute only a small fraction of the components on mixed-signal ICs and emerging systems-on-a-chip (SoC) designs. But due to the increasing levels of integration available in silicon technology and the growing requirement for digital systems to communicate with the continuous-valued external world, there is a growing need for CAD tools that increase the design productivity and improve the quality of analog integrated circuits. This paper describes the motivation and evolution of these tools and outlines progress on the various design problems involved: simulation and modeling, symbolic analysis, synthesis and optimization, layout generation, yield analysis and design centering, and test. This paper summarizes the problems for which viable solutions are emerging and those which are still unsolved     

Computer-aided design in civil engineering

The paper reviews the development and current status of computer-aided design (CAD) in structural-engineering, a branch of civil engineering. The Similarities to and differences from electrical engineering practice are emphasized. The presentation deals first with well-developed CAD application areas, namely those supporting analysis, component selection and the preparation of design documents, Problematic areas, still subject to intense research, in synthesis, optimization, the representation of design specifications, the use of databases and the role of software engineering tools are briefly described.     

Analysis and application of NRD-guide excitors

In this paper, the NRD-guide excitors using a length of coaxial line which consists of a rectangle external conductor and a thin round inner conductor are presented, and the characteristics of the input impedances of LSE ₁₁ ^o mode and LSM ₁₁ ^o mode at the insertion points are analysed and calculated by using the method of the rector Green's function respectively. The computation results show that the mode excitors are able to improve the operating modes matching between NRD-guide and the quasi-TEM transmission line. The structures are suitable for fabrication LSE ₁₁ ^o mode oscillator and LSM ₁₁ ^o mode oscillator to compose millimeter wave NRD-guide integrated front ends. An example of an LSE ₁₁ ^o mode oscillator in Ka-band is given. Its oscillation frequency and output power could be easily adjusted by changing the parameters of the excitor.     

Computer-aided design of VLSI FIR filters

A CAD tool is presented for producing very high-throughput FIR filters. Because the CAD tool is application-specific, it is a very high-level tool. An engineer only needs to specify 1) the filter order, N; 2) the input word size; and 3) the output word size. Using this information, the CAD tool generates CIF files for a filter system that can process 10N million samples per second. The purpose of the paper is to illustrate the benefits of applying both bit-level systolic array architecture and application-specific CAD to the problem of FIR filtering. The resulting CAD system reduces the costs of very high-throughput FIR filters with respect to design, fabrication, and operation.     

Recent development in NRD-guide technology

Recent achievements in the field of the NRD-guide integrated circuits and antennas are reviewed. The main emphasis is placed on a new class of planar antennas which employ a leaky NRD-guide as the feed medium and can be contained in a common housing together with the NRD-guide integrated circuits.     

Computer-aided design: limitations in automating design anddrafting

The impact of CAD (computer-aided design) on employment and skill is examined. First, the relationship between the adoption of mechanical CAD systems and employment of drafters in the aerospace and automobile industries is assessed. Contrary to many employment projections, drafting employment in these industries increased with increases in the adoption of CAD systems. Second, the effects of design automation and skill transformation capacities of electronic CAD systems on printed circuit board designers are evaluated. Third, the limits to automation of design are explored, suggesting that there are trade-offs between automation of the design process and innovation in product design. The logical limits of software, flaws in programming, and the dynamic nature of product markets are evaluated as factors limiting automation     

Computer-aided design tools in chemical engineering process design

This paper reviews the design activity for chemical engineering process design, starting from the earliest step of selecting which products to manufacture and ending with designing the operating procedures for a process plant. At each step we discuss computer-aided design tools which have been or are being developed. Throughout synthesis aids which help make discrete design decisions are contrasted with analysis aids which help to select the proper values for continuous variables. Computer aids are abundant to aid in process design. The future holds promise for an integrated design tool which will aid the engineer from start to finish in his task.     

Computer-aided design and application of integrated LC filters

In this paper, methods of design and application of an integrated inductor-capacitor-transformer (LCT) are presented. A generalized modeling approach is also described. On the basis of this model and by using practical data, CAD software is developed for LCT, Several integrated LC and LCT samples were designed, built, and tested. Finally, a resonant power converter, using the integrated LCT, was built and tested     

Computer-aided design and analysis of direct-driven wheel motordrive

This paper presents the computer-aided design (CAD) and performance analysis of a novel direct-driven wheel brushless DC motor drive for electric vehicles (EVs). The proposed motor is a permanent magnet square-wave motor, whose rotor with rare earth magnets forms the exterior of the motor, which can be fitted with a wheel tire to realize the direct drive for each wheel of an EV. The interior stator with its windings is rigidly mounted onto the suspension and frame structure of the vehicle. In order to achieve the direct drive without any mechanical transmission for EVs, the wheel motor has been designed as a low-speed high-torque motor. The design and optimization of the motor geometry was achieved with the aid of finite-element electromagnetic field analysis. Simulation studies on the transient performance of the motor drive were also carried out. This involved the creation of the motor transient model and formulation of a motor control strategy to ensure the wheel motor drive runs efficiently in the entire permitted speed and load range. The application of CAD techniques in the design of this very unconventional drive is described in this paper     

Computer-aided analysis and design of circular waveguide tapers

Two computer programs have been developed for the rigorous performance analysis of circular waveguide tapers. They are based on the direct integration of the coupled wave equations and on a mode-matching procedure applied to a step-ladder equivalent of the taper, respectively. Close agreement has been obtained between the predictions of these two approaches. The computer programs are utilized to examine the usefulness of existing taper design procedures. It has been found that a Dolph-Chebychev design is actually capable of predicting the level of the first unwanted mode, provided that the operational frequency is far above its cutoff. The spurious mode excitation can still be improved by taking into account the reconversion of power from the unwanted into the wanted modes. It has been verified by the computer analysis that the above design procedures are applicable even for frequencies near cutoff of the dominant spurious mode; however, that is at the expense of a certain degradation of the input reflection of the incident mode. A further improvement of the performance is possible only by direct computer optimization of the taper