A. James Clark School of Engineering

Permanent URI for this communityhttp://hdl.handle.net/1903/1654

The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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Subject: search.filters.subject.CAD

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Now showing 1 - 4 of 4
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    Development of a CAD Model Simplification Framework for Finite Element Analysis
    (2012) Russ, Brian Henry; Gupta, Satyandra K; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Analyzing complex 3D models using finite element analysis software requires suppressing features/parts that are not likely to influence the analysis results, but may significantly improve the computational performance both in terms of mesh size and mesh quality. The suppression step often depends on the context and application. Currently, most analysts perform this step manually. This step can take a long time to perform on a complex model and can be tedious in nature. The goal of this thesis was to generate a simplification framework for both part and assembly CAD models for finite element analysis model preparation. At the part level, a rule-based approach for suppressing holes, rounds, and chamfers is presented. Then a tool for suppressing multiple specified part models at once is described at the assembly level. Upon discussion of the frameworks, the tools are demonstrated on several different models to show the complete approach and the computational performances. The work presented in this thesis is expected to significantly reduce the manual time consuming activities within the model simplification stage. This is accomplished through multiple feature/part suppression compared to the industry standard of suppressing one feature/part at a time. A simplified model speeds up the overall analysis, reducing the meshing time and calculation of the analysis values, while maintaining and on occasion improving the quality of the analysis.
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    VLSI CAD Tool Protection by Birthmarking Design Solutions
    (IEEE, 2005-04) Yuan, Lin; Qu, Gang; Srivastava, Ankur
    Many techniques have been proposed in the past for the protection of VLSI design IPs (intellectual property). CAD tools and algorithms are intensively used in all phases of modern VLSI designs; however, little has been done to protect them. Basically, given a problem P and a solution S, we want to be able to determine whether S is obtained by a particular tool or algorithm. We propose two techniques that intentionally leave some trace or birthmark, which refers to certain easy detectable properties, in the design solutions to facilitate CAD tool tracing and protection. The pre-processing technique provides the ideal protection at the cost of losing control of solution’s quality. The post-processing technique balances the level of protection and design quality. We conduct a case study on how to protect a timing-driven gate duplication algorithm. Experimental results on a large set of MCNC benchmarks confirm that the pre-processing technique results in a significant reduction (about 48%) of the optimization power of the tool, while the post-processing technique has almost no penalty (less than 2%) on the tool’s performance.
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    Computer Aided Design of Wide-Band Microwave Components
    (2007-11-27) Fahmi, Mohamed Mohamed; Zaki, Kawthar A; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    In recent years there was a notable developmental leap in communications systems operating at microwave frequencies. In the dissertation, the goal is to demonstrate the challenges and to propose solutions that enable the successful design and realization of very wide band microwave components, in particular, microwave directional couplers and filters. Directional couplers are an essential part in microwave systems. They are commonly used for dividing or combining signals. For example they are used in the generation of the desired power division in beam-forming networks for spacecraft antennas. In other applications, they are used for power monitoring. In the dissertation, a comprehensive treatment of wide-band ridge waveguide directional couplers is included. Analysis and design of different configurations and arrangement of couplers realized in ridge waveguides are discussed. A new detailed systematic design procedure for ridge waveguide couplers in the two most used configurations "E-plane and H-plane" is proposed. Filters are also an integral part of any communication system. They separate communication channels operating at different frequencies thus eliminating interference between different channels. In the dissertation, design issues of wide-band ridge waveguide elliptic function filters realized in Low Temperature Co-fired Ceramics (LTCC) are discussed. Ridge waveguide filters have excellent characteristics such as wide stop-band and compact size. An excellent approach in manufacturing RF/microwave systems is the integration of components into multilayer substrates using LTCC which facilitates the design of microwave modules in the same package thus increasing reliability and reducing size. A new scheme to achieve the strong couplings, a crucial requirement for the realization of wide band elliptic filters is proposed in the dissertation. As an example, rigorous mode matching method is successfully used in the analysis and design of a challenging wide-band ridge waveguide filter realized in LTCC technology. Another interesting realization of couplers is the realization in strip-line transmission lines. In the dissertation, new proposed multi-section multi-layer LTCC stripline couplers are designed and analyzed. The proposed design enables the designer to achieve precise performance otherwise restricted by limitations posed by available technologies. The realization of wideband performance is made possible by such proposed design.
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    Modeling and Design of Microwave-Millimeterwave Filters and Multiplexers
    (2006-11-27) Zhang, Yunchi; Zaki, Kawthar A.; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Modern communication systems require extraordinarily stringent specifications on microwave and millimeter-wave components. In mobile and integrated communication systems, miniature, ultra-wideband and high performance filters and multiplexers are required for microwave integrated circuits (MICs) and monolithic microwave integrated circuits (MMICs). In satellite communications and wireless base stations, small volume, high quality, high power handling capability and low cost filters and multiplexers are required. In order to meet these requirements, three aspects are mainly pursued: design innovations, precise CAD procedures, and improved manufacturing technologies. This dissertation is, therefore, devoted to creating novel filter and multiplexer structures, developing full-wave modeling and design procedures of filters and multiplexers, and integrating waveguide structures for MICs and MMICs in Low Temperature Co-fired Ceramic (LTCC) technology. In order to realize miniature and broadband filters, novel multiple-layer coupled stripline resonator structures are proposed for filter designs. The essential of the resonators is investigated, and the design procedure of the filters is demonstrated by examples. Rigorous full-wave mode matching program is developed to model the filters and optimize the performance. The filters are manufactured in LTCC technology to achieve high-integration. In order to obtain better quality than planar structures, new ridge waveguide coupled stripline resonator filters and multiplexers are introduced for LTCC applications. Planar and waveguide structures are combined in such filter and multiplexer designs to improve the loss performance. A rigorous CAD procedure using mode matching technique is developed for the modeling and design. To design wideband multiplexers for LTCC applications, ridge waveguide divider junctions are presented to achieve wideband matching performance. Such junctions and ridge waveguide evanescent-mode filters are cascaded together to realize the multiplexer designs. The design methodology, effects of spurious modes and LTCC manufacturing procedure are discussed. Additional important issues of microwave filter and multiplexer designs addressed in this dissertation are: (1) Systematic approximation, synthesis and design procedures of multiple-band coupled resonator filters. Various filter topologies are created by analytical methods, and utilized in waveguide and dielectric resonator filter designs. (2) Dual-mode filter designs in circular and rectangular waveguides. (3) Systematic tuning procedure of quasi-elliptic filters. (4) Improvement of filter spurious performance by stepped impedance resonators (SIRs). (5) Multipaction effects in waveguide structures for space applications.