LC is simulation tool for the analysis of the electromagnetic properties of electrical interconnects. The full three-dimensional circuit is modeled, so all interactions are automatically included in the solution. The model can be excited by numerous types of waveforms, and the transient response measured using common values such as voltage and current. Circuit parameters such as inductance, capacitance, and impedance can be derived from the transient response, and frequency-domain results such as S-parameters can also be calculated. Far field radiation patterns can be obtained.
LC is primarily an electromagnetic simulation and uses the Finite-Difference Time-Domain (FD-TD) technique. FD-TD is a full wave explicit solution of Maxwell's equations in three dimensions. In FD-TD, the rectangular volume enclosing the model is discretized into a large number of small cells, which may be uniformly-sized, or may vary in size within the simulation space. The dielectric, permeable, lossy, and conducting material properties of each cell are incorporated into the field updates, which are performed iteratively in small time steps.
An interface between the electromagnetic simulation and the circuit simulation program SPICE is available within LC. This allows the user to add arbitrary SPICE circuits, such as drivers and loads, into the interconnect model. The interconnect performance is calculated using the electromagnetic simulation, while the lumped-element circuits are evaluated by SPICE. Both simulations are performed in the time domain, and proceed in lock step.
LC was orignally developed by Cray Research as an internal design tool. Like many projects, this one has a long roster of contributors from a variety of organizations.
LC has been used internally at SGI for the analysis of computer systems for electromagnetic compatability, and for design of high speed interconnect systems. It is also used for research and education at the University of Colorado at Boulder and San Francisco State University.
LC is being distributed in executable form for users of SGI and Cray Research computers. It is available without cost, and is unsupported software. LC is in use at over 50 sites, of which about half are universities, and the balance companies and government organizations.
The lc-users mailing list is an open forum for discussions about LC.
LC is an integrated model editor, simulator, and analysis tool. It's composed of 150,000 lines of C++ and Fortran, uses OSF/Motif, and is portable to most Unix-based computers. Its companion plotting program, LCPlot, is also included in the executable distribution. The simulator has fully dynamic memory allocation, and can use multiple processors in parallel to reduce the time to solution.
Also included is SPICE 3, the circuit simulator from the UC Berkeley CAD group. Both LC and FDTD can call SPICE 3 when a combined electromagnetic and circuit simulation is performed.
A number of enhancements were addded to LC during 1998 based on the valuable feedback from the users. Non-cubic and variable-size cells can now be included in the simulation grid. Improvements for visualization include contour plots and refined interpolation. Sphere-shaped primatives were added, and blocks can now be rotated arbitrarily to model diagonal traces or other complex geometry. The far-field calculation capability has been extended with many new options. Many ease-of-use and model integrity features were also added.
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