4. Impedance measurement

There are many different methods of measuring impedance. For frequencies below around 1 GHz, there are three different impedance measurement methods. Above this frequency, impedance measurement is mainly carried out using network analyzers operating in the frequency or time domain. To define an impedance, we need to consider two cases:

• when the signal wavelength is large relative to the device under test, as well as its access points for connection to the measuring device;

• when the signal wavelength is of the same order of magnitude, or even smaller, than the device under test.

• In the first case, we can precisely define the physical accesses of the device under test; impedance is then defined as the ratio of voltage and current across the device....