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The conventional approach to EM modeling requires a designer to develop an equivalent circuit topology based on the geometry of an EM structure. Then the designer must tweak the values of circuit elements to obtain the best fitting response. If tweaking does not generate a good agreement with the response of the structure, the topology is discarded and a designer goes through the same process again with a new circuit topology. However, this is a very time consuming and tedious approach that is heavily dependent on the designer's skill and experience.

EMtoSPICE is a software tool that converts scattering parameters (S-parameters) to broadband SPICE macromodels (or subcircuits), allowing simulation of any device using its S-parameters in SPICE. EMtoSPICE accepts S-parameters in Touchstone format or raw data format. S-parameters may be obtained from measurements, full-wave EM solvers or any RF analysis/simulation tools. A macromodel generated by EMtoSPICE may be combined with other devices in SPICE for simulation in time domain or frequency domain.

For the users of HSPICE®, EMtoSPICE generates macromodels that are optimized for speed using LAPLACE and rational functions (quotients of two polynominals). For the users of all other SPICE simulators (PSPICE® for example), EMtoSPICE generates macromodels in General SPICE Format using lumped elements (R's, L's and C's) and controlled sources.

EMtoSPICE does not need a full set of data to generate a macromodel. Only a limited sample of data is needed because EMtoSPICE interpolates data. This is a useful feature since a full-wave EM simulation may often require a long simulation time even with modern computing resources. Obtaining data at a small number of frequency points reduces EM simulation time. Of course, a full set of S-parameter data may be used if it is available.

Typical applications include modeling or characterization of RF components, IC packages, PCB's, cables, connectors, etc.

The following diagram gives overview of how EMtoSPICE may be used.

flow chart

EMtoSPICE can generate highly accurate models over broadband frequencies. The figures below show examples of interpolation using EMtoSPICE. Very few tools can imitate the accuracy and bandwidth that EMtoSPICE is capable of.

Magnitude of S13 Phase of S13 Figure 1: An interpolation example of a stripline

Magnitude of S13 Phase of S13 Figure 2: An interpolation example of a coupled traces in adjacent layers in a multilayered board

Magnitude of S11 Magnitude of S21 Figure 3: An interpolation example of an interdigitated capacitor