Separating dc resistance from PCB trace characteristic impedance measurement.

Though both measured in Ohms, it may come as a surprise that characteristic impedance and dc resistance are not the same:

0:00 Welcome and introduction
0:30 Controlled impedance traces on PCBs
0:35 Impedance of coax cable
1:20 Simulated coax cables on PCBs
1:50 Simulation v measured impedance
2:30 DC resistance clouding measurement on fine line traces
2:57 DC resistance in cables – rising traces
3:46 De-embedding DC resistance from impedance measurements
4:45 Modelling the DC resistance and simulating the effect on a TDR trace
6:00 Launch Point Extrapolation
6:45 CITS DC resistance compensation
7:25 Summary

This presentation at the EIPC Summer conference shows you how to untangle one from the other. Both are important specifications but should not be combined.