CST2013: Frequency Domain Solver Sampling 

Simulation: Solver Start Simulation Frequency Domain Solver Frequency samples: Properties

Interpolative frequency sweep frame

Stop if error criterion is met: If the broadband frequency sweep (see the frequency samples frame in Frequency Domain Solver Parameters) is enabled and automatically chosen frequency samples are defined, the solver stops calculating additional frequency samples as soon as an error criterion is met, which is defined by the options listed hereafter.

S-parameter error threshold value: The value serves as a termination criterion for the broadband frequency sweep. It usually refers to the maximum deviation of the linear S-parameters between two successive Frequency Domain solver runs. Please note that for the distributed calculation of frequency samples, the broadband sweep is usually applied after a certain number of frequency samples have been calculated. See the section Distributed computing and adaptive sampling in the Frequency Domain Solver Overview for details.

The progression of this error measure is appended to the result tree:

By default, all S-parameters are taken into account. Evanescent modes can be excluded by specifying a zero Weight for evanescent modes below. Uncheck Consider all S-parameters to select S-parameters which then will be considered for the error criterion.

Number of error threshold checks: The value serves as an additional termination criterion for the broadband frequency sweep. Because the convergence of the S-parameter sweep's error measure is not necessarily monotonic, it is recommended to check the convergence a couple of times (twice by default).

Minimum number of samples: This option allows you to specify a minimum number of frequency samples that are calculated without terminating the broadband sweep, even if the S-parameter sweep error criterion is already met.

Weight for evanescent modes: When the frequency range includes cutoff frequencies of some waveguide ports, and the S-parameters related to these modes are of minor interest below cutoff, this weight factor can be set to a value less than one. This has the potential of accelerating the S-parameter sweep. The default error weight is one, meaning that evanescent modes are considered just as important for the S-parameter sweep as propagating modes.

Frequency sweep frame

Consider all S-parameters: If this option is enabled, all S-parameters are taken into account when calculating the S-parameter sweep error criterion, and the estimated error of all S-parameters determines where the next automatically chosen frequency sample is placed. Whenever some S-parameters are not required to be highly accurate, e.g., for higher order modes, a faster S-parameter sweep convergence might be achieved by de-selecting this option. Thereafter, a list of S-parameters to consider will be shown. For instance, to focus on the transmission of a two port device, select

Number of interpolated samples

The number of interpolated S-parameter frequency samples is related to the resolution of the equidistantly evaluated S-parameter curves by

Increasing this number does not significantly increase the time required for the simulation. Please note that it is possible to recalculate the broadband S-parameter curves with a higher number of samples as a postprocessing step.

Resonant: Fast S-Parameter sweep frame

This option is only available for the Frequency Domain solver with tetrahedral mesh. Enable Run after adaptive mesh refinement if applicable to let the general purpose solver stop after the adaptive mesh refinement without performing the interpolative sweep. Afterwards, the fast resonant solver method will be executed to calculate the broadband results. This is an alternative and efficient way of using the fast resonant solver method, especially if the faster single point adaptive mesh refinement of the general purpose method is preferred. If a required feature prevents the fast resonant solver from being applied, the default interpolative sweep is used. The solver log file provides a hint about the missing features, which possibly can then be removed (for instance, some field monitors which are unsupported by the fast resonant solver.)

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