STOP DC resistance clouding your high speed measurements

Remove DC trace resistance errors from characteristic impedance measurements

“Surely characteristic impedance and resistance are the same as they are both measured in Ohms?”

In fact, they are both important parameters of a transmission line – but only have the same units because of a convenient coincidence of the laws of physics.

This video shows how to avoid the DC resistance of a transmission line causing errors in your measurement of the line's characteristic impedance. Both are important specifications but they should not be mixed up with each other.

Contents

00:00 Welcome and introduction
00:30 Controlled impedance traces on PCBs
00:35 Impedance of coax cable
01:20 Simulated coax cables on PCBs
01:50 Simulated v Measured impedance
02:30 DC resistance clouding measurement on fine line traces
02:57 DC resistance in cables – rising traces
03:46 De-embedding DC resistance from impedance measurements
04:45 Modelling the DC resistance and simulating the effect on a TDR trace
06:00 Launch Point Extrapolation
06:45 CITS DC resistance compensation
07:25 Summary