C_GRID

	C_GRID Data Item Coplanar Grid Data Definition Perameters Notes
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Coplanar Grid Data Definition

In this data item, grid and simulation control data are defined for the implemented Finite Difference-Solver. Parameters like simulation box size, discretization mesh size, error boundry for the numerical iteration and the maximum deviation of structure dimensions from grid can be specified.

Parameters

Parameter	Discreption	Range of Usage
BOUND	Maximum iteration error used by iterative solver	1E-06 £ BOUND £ 1E-02
L1	Width of shielding box (L1=- 1, - 2 ® auto sizing)	see notes of related element
L2	Length of shielding box (L2=- 1, - 2 ® auto sizing)	see notes of related element
DL	Size of smallest grid element	> 0
ACC	Maximum deviation from grid in %	0 £ ACC £ 100

Notes

BOUND is the maximum iteration error for the applied "Over Relaxation Method", which can be specified by theuser. Following table shows the influence of this parameter on simulation time and accuracy of results for a coplanar cross junction. The time and error values are related to the results for BOUND=10^-6. A value of 10^-3is recommended for a first run simulation. For the final analysis, a BOUND=10^-4 is always sufficient (see chapter 2 for more detailed information on this subject).

No.	BOUND	Simulation Time Related to No. 5	Error Related to No. 5
1	10^-2	9 %	60 %
2	10^-3	28 %	2.5 %
3	10^-4	54 %	0.3 %
4	10^-5	77 %	0.03 %
5	10^-6	100 %	0 %

L1 and L2 are the shielding box dimensions, which effect the accuracy of the results. In order to keep these effects as small as possible, L1 (Box width) and L2(Box depth) should be as large as possible. The simulator adapts the box sizes on the structure automatically if L1 and L2 are set to –1 or –2. The following table shows the possible combinations for L1 and L2 (for BOUND=10^-4) and their effect on the accuracy and simulation time.

No.	L1	L2	Simulation Time Related to No.4	Error Related to No. 4
1	–2	–2	14 %	8 %
2	–1	–2	36 %	7 %
3	–2	–1	36 %	6 %
4	–1	–1	100 %	0 %

In cases where user like to investigate the shielding effects on structure characteristics, Box sizes can be specified manually. For such applications, the minimum values for L1 and L2 (given in the notes of the related element) and their compatibility to the grid (see below notes) are. Manually selected box sizes could lead to errors if the user optimize the structure dimensions, since in this case the box size is not automatically adapted to the changed dimensions.
The parameter L2is ignored for the elements: C_LIN, C_METVIA, C_TFG, C_TFR, C_MIM, C_CAPLIN.
DL is the external grid size and represents the smallest mesh used by the discretization of the structure. The internal grid size is DL/2. The metallization edges of the structure have to lie on grid points, this means that the structure dimensions have to be an integer multiple of DL/2. A (DL=1/2 of the smallest structure dimension) is recommended.
ACC presents the deviation of the structure parameters from grid mesh. Normally the structure edges have to lie on grid points. However, it is possible to simulate structures with arbitrary dimensions. In this case the user can specify a maximum deviation from grid size ACC. The simulator adapts the incompatible structure dimensions into the grid by changing these dimensions slightly (warnings will be reported). For ACC=0 (no deviation from grid) the simulator reports error and the next compatible value will be suggested in the error message. These changes are not considered by automatic layout generation. In order to avoid any discrepancies between simulation and layout, a value of ACC=0 is recommended.
The value for metallization thickness t_n (n=1,2) and dielectric height die_h_n (n=0,1,2) can be independent from grid size DL. However, for these two parameters, the ratio t/DL and die_h /DL should be between 0.2 and 5.0. Otherwise, the accuracy of the simulation can not be guaranteed.