There are many questions about measuring Power Delivery Networks (PDN), but these two are very common ones. Why do we calibrate the 2-port measurement with a 1Ω shunt resistor and why do I use DC blockers on both ports? In this article I’ll provide responses to both of these questions. The measurement setup in Figure 1 is an example where I used both the 1Ω calibration and the inclusion of the DC blockers.