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From this link I understand the definitions of a Maxwell matrix and a SPICE matrix

Maxwell and Spice Matrices - ANSYS

However, what is the meaning of a negative main-diagonal entry in a SPICE matrix? Since the main diagonal element in this matrix is the self-capacitance or the capacitance between this point and ground on a PCB. For example, I have this matrix from a parasitic extraction simulation I ran,

EDIT 1:

Here is the maxwell matrix which confirms the values of the cap to Ground value, enter image description here

enter image description here

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  • \$\begingroup\$ What does your Maxwell matrix look like? \$\endgroup\$
    – Ste Kulov
    Commented Aug 5, 2022 at 15:15
  • \$\begingroup\$ @SteKulov edited the answer, thanks! \$\endgroup\$
    – SM32
    Commented Aug 6, 2022 at 17:18
  • \$\begingroup\$ I don't know enough regarding the tools/software you're using, but it sounds like the physical phenomena you're modeling for simulation is best done using things not physically realizable such as a negative capacitor. On the other hand, a SPICE simulator has no problem using the negative values in its internal calculations. The only thing that changes is the phase response, since a negative C changes \$\frac{1}{j \omega C}\$ to \$\frac{j}{\omega C}\$. \$\endgroup\$
    – Ste Kulov
    Commented Aug 7, 2022 at 4:15

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