2.3 Crosstalk Model Consider two coupling nets in Fig. 1(a). They can be modelled as a circuit shown in Fig. 1(b). In this figure V1and V2 represent the voltages at the output of the sources/driver which are the two net R1 and R2 represent the source resistance. C represent the coupling capacitance between the net, where as C1 and C2 represents all other capacitance. The crosstalk affect on net 2 can be thought of as the difference of voltages on node O with or without the signal switching in net 1. Here, we can find that besides the coupling capacitance C, the crosstalk effect also depends on the driver strengths (R1 and R2), other load capacitance (C1 and C2) , and the voltages (v1 and v2).
************************ Fig.1:Modeling Two Coupling Nets
For a net, the crosstalk effects from other nets may not happen at the same time. Characterizing all cases requires exhaustive analysis which depend on crosstalk. In the worst case, we can use the summation of all the effects from other nets as the total crosstalk on on one net. Cij represents the coupling capacitance between net, i and j That is
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For each net i, the crosstalk coefficient (eij) from net j is a real number Eij***. Generally speaking, each element in a chip is coupled with every other element. However coupling capacitance decreases rapidly when an element is out of the neighbourhood of the other element. For interconnection, coupling capacitance between perpendicular wires is also very small and can be represented by the following formula.
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Where 1 is the length of gap, d is the distance between coupling nets, and beta is a constant which was estimated to be about 2 in [6].