Make Accurate Impedance Measurements Using a VNA (.PDF Download)

A vector network analyzer (VNA) is a very useful test instrument for characterizing RF circuits and amplifiers. But what about measurements of simple passive components? What’s the best way to characterize a chip capacitor or an inductor—or even a resistor?

In the past, without giving it much thought, this author has measured chip capacitors by grounding one end. After doing a careful port extension to the end of a homemade probe, the cap would be measured with the Smith chart mode engaged and read off the value from an R + jX marker. As it turns out, this method is only appropriate for a narrow range of component impedances and this measurement probably had significant error.