The difficulty of assessing these impedances increases with frequency.Ī: A sophisticated test instrument called a vector network analyzer (VNA), as well as a test suite are used ( Figure 1.) The VNA sweeps across the frequency range of interest, measures the impedance, and then provides a table or graphical representation of the results. In these cases, impedances must be measured. In many cases, impedances must be determined by a detailed model of the circuit and its many elements, which is a difficult task for high-frequency RF.
In some cases, such as individual components, the vendor provides this data however, parasitics and other in-circuit factors will change these values. Q: What are the challenges in impedance matching?Ī: The first challenge is figuring out what the source output impedance and load impedance actually are. The Smith chart is a very helpful graphical tool for developing the matching network. It may seem that doing a few calculations using a software package is all that is needed, but the reality is far more complicated. Once the need for an impedance-matching network is determined - and it is very likely needed - the next challenge is defining and creating this network. Part 1 looked at impedance matching and the need for a complex conjugate impedance at the load, compared to the source impedance.
