CST2013: Special Integral Equation Solver Parameters 

Simulation: Solver Start Simulation Integral Equation Solver Specials

In this dialog the properties of the Integral Equation Solver simulation can be specified. For most simulations the default settings should be used.

General frame

Solver order: This option allows to specify whether the integral equation solver uses first-, second- or third-order accuracy. First-order is the default. If the structure is geometrically complex and therefore comes along with huge memory requirements, first-order is the best choice. A calculation with higher order provides higher accuracy (requires most memory). If a mixed order is specified the solver chooses the most appropriate order for each triangle automatically.

Use double precision: If activated the solver uses double-precision (64-bit) for representing floating-point values. Otherwise the solver uses single-precision (32-bit). The single-precision representation saves memory whereas the double-precision representation might speed up the convergence of the iterative equation system solver.

Fast RCS sweep: A fast calculation of monostatic RCS for different angles is available if a plane wave is used as excitation. To enable and disable the fast RCS calculation check and uncheck this option respectively. Use the monostatic RCS sweep settings to customize the RCS calculation.

Treat electric and magnetic boundary cond. as infinite ground plane (XMin, YMin, ZMin):  If this option is checked and an electric or magnetic boundary condition is defined for XMin, YMin or ZMin this boundary will be considered as infinite ground plane. If it is unchecked the boundary will be meshed if an electric boundary condition is defined and an magnetic boundary condition will be handled as open boundary condition.

This option is supported by all linear equation system solver except the iterative (MLFMM)  and iterative ( MLFMM)  AP solver.

Low frequency stabilization: This option controls the low frequency stabilization for the iterative and direct MoM solver. If enabled the accuracy for electrically small models or models with small triangles compared to the wavelength will increase. Please note that this option is not compatible with MLFMM.

Linear solver frame

Solver type: This option allows you to specify whether an

• iterative (MLFMM)

• iterative (MoM)

• direct

linear equation system solver should be used.  The iterative (MLFMM) solver is advantageous for large problems. For simulations with only few surfaces (and hence only small number of degrees of freedom) the direct solver should be used.

As a default, the integral equation solver automatically chooses the solver type.

Maximum number of iterations: Terminates the solver after the given number of iterations by enabling this option.

Preconditioner: This option specifies the preconditioner for the iterative linear equation system solver.

• The default value is "Auto". Chooses automatically one of the following preconditioner.

• For most applications the preconditioner "Type 1 (AP)" is the best choice in terms of calculation time, memory requirements and number of iterations.

• For simulations with several excitations per frequency point the preconditioner "Type 2 (SPAI)" might be the best choice  in terms of total calculation time.

• The preconditioner  "Type 3 (Diag)" is the most memory efficient choice.

For the preconditioner "Type 2 (SPAI)" a tolerance can be specified for the iterative (MLFMM) solver. The default value for the tolerance is 0.15. The smaller the tolerance of the preconditioner the better is the convergence and the more memory is required.

Materials frame

Activate the check button Constant, dispersion and surf. imp. fit as in Time Domain to consider the fit procedure of the tangent delta settings in the Material Parameter Conductivity Dialog using a dispersive Debye model correspondent to the time domain. By deactivating this button, the constant fit option is realized as a constant tangent delta over the complete frequency range while a dispersive fit results in a linear interpolation between the defined loss angle values.

The setting affects also the treatment of ohmic sheet. With this button activated the ohmic sheet impedance will be computed accordingly to the same fitting scheme used for the time domain solver. Otherwise a constant (frequency independent) value of the impedance will be applied.

The setting also affects the treatment of dispersive materials if the model simplification is configured so that lossy materials are treated as lossfree.

PEC solid handling: Select here the formulation for closed PEC solids The default is CFIE. The faster convergence of the linear equation system solver is an advantage of this option.

For electrically small or complex PEC solids it is recommended to select the alternative CFIE formulation. The accuracy for rather coarse mesh will be improved.

Also for electrically small PEC solids the EFIE formulation can be used. Be aware that EFIE does not suppress spurious resonances as the other two options do. Spurious resonances can appear for structures which are not electrically small.

Iterative solver frame

MLFMM accuracy: This accuracy determines the accuracy of the coupling between the boxes. A lower accuracy leads to lower memory requirement but also to a lower accuracy.

Minimum Box size in wavelength: Depending on the frequency at each simulation point the box size of the MLFMM is choosen automatically. This option allows you to specify the minimum box size the MLFMM can use. A smaller box size might lead to more levels in the MLFMM; which decreases the near field memory and increases the far field memory.

If the box size is too small the results show a low accuracy.

Iterative MoM accuracy: This accuracy determines the accuracy of the system matrix. A lower accuracy leads to lower memory requirement but also to a lower accuracy.

OK

Accepts the input and closes the dialog.

Cancel

Closes this dialog box without performing any further action.

Help

Shows this help text.