Vector network analysis for nonlinear systems

Introduction The measurement of the nonlinear behavior of microwave systems and components has evolved a lot over the last years. Starting from instrument prototypes, vector network analyzers for nonlinear systems (NVNA) have now entered the product lines of all the major instrumentation vendors. The major challenge for the scientific community is to embed these devices in the mainstream design and characterization of nonlinear devices and circuits. As the NVNA is still young, most currently active professionals did not experience NVNA technology during their education or their career. Therefore, it is extremely important to clearly define what can be expected from an NVNA. There is a need for an explanation of what an NVNA is and is not. Explaining the limitations of the NVNA technology is also extremely important, as this can avoid false expectations and deceptions. This text has the ambition to take a small step in this direction. This is why much effort is spent in the first sections of this chapter in drawing the big picture around the NVNA. Our hope is that this might help practitioners to position the NVNA and to obtain some intuition about the actual measurements the NVNA makes. The remainder of the text explains the ideas behind the different instruments that have NVNA capability. The setups are very different, but the measurements they make are very similar. The key idea is that to characterize a nonlinear device under test, one needs to measure the complete spectrum (amplitude and phase) of all the port quantities (waves or voltages and currents) that are present at all the ports of the device.