Measure PDN on a budget

As the use of microcontrollers, CPUs and FPGAs continues to grow, more engineers are facing challenges with their power distribution network (PDN) design. Many engineers are just starting to perform PDN measurement.  Typically, these measurements are performed using a vector network analyzer (VNA).  A 1-port measurement can be used for impedance levels above a few hundred m?.  A 2-port shunt-thru measurement is used for applications as low as 1m? and in some cases even lower.  Both of these measurements are based on S-parameters, allowing the cable to match the instrument impedance all the way to the point of measurement. (For background on s-parameters, head to the S-parameter collection on EDN).

There are many good analyzers available for measuring PDN High performance VNAs are available from all of the major test equipment manufacturers, including Agilent, Tektronix, Teledyne Lecroy, and Rohde & Schwarz.  Most product lines include offerings of S-parameter measurements up to 40GHz or higher.

Many of these are above our price range While these are all excellent instruments, and I use them myself, we don’t all have a budget that can support such an expense.  There are other options available. If you only need an instrument for a short time, you might consider renting one from one of the many test equipment rental companies.  Depending on your measurement requirements, you might be able to make use of some lower cost instruments, two of which we will discuss in this article.

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