An Evaluation of Differential Impedance in PCBs Using Two Single-Ended Probes Only

There is an emerging need to measure differential transmission lines in printed circuit boards (PCBs). However, conventional measurement techniques are not simple because they require broadband baluns or matched termination. In this paper, we suggest a simple measurement technique using two coaxial probes only. To validate the method, coupled microstrip lines were tested. The results show very good agreement with those from the conventional methods. The rationale of this method is also clearly stated. Finally, it is reconfirmed by the full-wave simulation.