A. The Active Load-Pull Measurement System

In order to evaluate and match the optimum load of multi-finger high-power transistors the following active load-pull system was established and used to match transistors of ${\it W}_{\mathrm{g}}$= 480 $\mu$m and beyond in the Ka-frequency band (26.5 GHz-40 GHz).

Figure A.1: Active load-pull system for 26.5-40 GHz.

The system follows a description given in [298]. A Traveling Wave Tube (TWT) Amplifier is used with a minimum output power of 40 dBm and minimum gain of 50 dB. Devices with an output power up to ${\it P}_{\mathrm{sat}}$= 352 mW have been be characterized in the Ka-band.