# The meaning of RLGC matrix in Sonnet software

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#### mohandes79

##### Junior Member level 3 Hi all,

Just a simple question came across here. As Sonnet software computes RLGC matrix at desired frequencies, I was wondering how the matrix can be explained in terms of the R & L & G & C units e.g the capacitance is 1.2e-12 per unit length.
I am not sure that the software does convert the data to /meter or still needs to be considered as the unit length of the line?

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#### volker_muehlhaus

##### Guest I am not sure that the software does convert the data to /meter or still needs to be considered as the unit length of the line?

This depends on the Sonnet version. The old format in v11 and older is per analyzed length. Example: if your analyzed line was 1.2mm long, the values are per 1.2mm length.

The new model in v12 has values per meter.
Note that there where some issues with line length for RLCG extraction in v12.52. The later version (12.54 and 12.56) are fine.

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#### mohandes79

##### Junior Member level 3 Thanks for your reply Volker. There is slightly difference when we have a look at RLGC file at 1GHz and the plotted equation e.g Inductance. Is it because the equation is calculated based on PI model?

Do you think considering RLGC matrix would be much beneficial rather than plotting the equations?

Thanks

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#### volker_muehlhaus

##### Guest Which Sonnet version do you use?

#### mohandes79

##### Junior Member level 3 The sonnet version is 11.5

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#### volker_muehlhaus

##### Guest There is slightly difference when we have a look at RLGC file at 1GHz and the plotted equation e.g Inductance. Is it because the equation is calculated based on PI model?

The inductance2 equation interprets the series path between port 1 and 2 as an inductor with series resistor. For each frequency, the (effective) inductance is calculated from Y21. If you physically have an inductor with parallel C, the equation will show a frequency dependent inductor without parallel C.

The lumped PI model output in v11.52 works a little but different because it takes data from two frequencies, and from the frequency dependence calculates the L and C components of that parallel circuit.

For the RLGC output, I am not sure. I was thinking that in v11.52, calculating the L component works the same way as the inductance2 equation.

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