It is important to use the right equipment for the right measurement to get results that are accurate. Precision millimeter-wave (mmWave) measurements normally require a VNA with built-in capability or mmWave extenders to augment the frequency range. This equipment may be used to evaluate mmWave mixers which are commonly used to up-convert or down-convert 5G signals back and forth from baseband frequencies.
It’s also possible to analyze the performance of a mmWave mixer using a low-frequency VNA. Because the baseband IF frequency is often in range for a microwave frequency VNA, a “Reference” mixer can operate with the same Local Oscillator (LO) to generate the mmWave signal needed to analyze a Mixer Under Test (MUT).