An active load pull system is presented for measuring devices from 50 um to 1 mm gate width in Ka Band. It permits in a first configuration to measure the scattering parameters in small- and large-signal conditions. In the other configuration, it permits to extract all gains, power levels, impedances of interest, average currents and efficiencies for a given device, even for very large gate width. It can scan automatically the interesting area of the Smith chart. The system protects the tested devices because the impedance is presented at the output of the device only if the gate current is lower than a fixed value
