Lee A. Barford

Apparatus and method for computer-aided design of sheet metal fabricated parts

A CAD system and method for designing sheet metal parts. A proposed design is automatically tested against a set of design rules. Available tools are selected according to criteria computed with reference to the part to the fabricated and then are tested to determine whether they can be used to make desired bends. A fabrication sequence is computed.

Fast time domain simulation in SPICE with frequency domain data

The capability of time domain simulation with frequency domain data exists in some time-domain simulators, but the computations can be time-consuming. We decrease this computational burden by exploiting S-parameter fitter and fast recursive convolution methods. With recursive convolution the frequencies at which the S-parameters are sampled may be spaced in any way. For example, a logarithmic frequency spacing allows S-parameters to be sampled over a broader band without increasing the number of frequencies measured. We use two different system identification techniques for extracting the closed-form equations describing measured or simulated S-parameter data. Lumped parameter systems are approximated as a rational polynomial modulated by a complex exponential. Distributed parameter systems are approximated by the sum of complex exponentials. The recursive convolution engine handles both forms. The HP SPICE circuit simulator has been extended to allow fast, recursive convolution methods to be employed for transient analysis. The resulting simulator is called SSpice v2. Significant speed-up in the simulation of several circuits have been achieved using this new technique compared to both the traditional approach in SPICE and our previous direct-convolution-based approach in SSpice v1. In this paper, we present the algorithms and applications of the simulator. Three applications are demonstrated in the paper which are MR head flex line modeling, chip-to-chip signal modeling on MCM, and on-chip inductor modeling.

Manufacturability tools: an engineer's use and needs

The Hewlett-Packard Company (HP) has successfully incorporated design for manufacturability (DFM) as a company philosophy by disseminating several assembly analysis techniques. HP is using the results of this philosophy to help identify future DFM needs. This work contains a history of DFM tools at HP, a discussion of the contributions, the shortcomings of these tools in the electronics manufacturing environment, and some recommendations to designers of DFM tools. For DFM tools to have a significant impact on manufacturing cost, design engineers must use them throughout the design process. The tools should be easy to use and provide the designer with beneficial analysis and advice.<<ETX>>

A parametric design assistant for concurrent engineering

The Explorer parametric design assistant, an interactive tool that provides intelligent support for searching concurrent-engineering trade-spaces under multiple, conflicting objectives, is described. The system provides a convenient means for specifying multiple, cross-disciplinary constraints in terms of tables, formulas, and logical sentences. Based on these data, the system performs interactive constraint checking, computes feasible designs, and provides graphical analysis facilities, allowing users to compare designs based on multiple criteria. As a first application, Explorer has been used as a printed circuit board (PCB) construction design assistant. In initial tests, Explorer has helped users to find design configurations not previously considered that yield comparable performance and cost while offering better manufacturability and reliability. The capabilities and use of the Explorer system are described in detail, the underlying technologies are outlined, and an evaluation of the prototype system is presented.